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The original directory structure was scattered and unorganized.
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diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
new file mode 100644
index 00000000..b7413cb4
--- /dev/null
+++ b/Documentation/filesystems/proc.txt
@@ -0,0 +1,1614 @@
+------------------------------------------------------------------------------
+                       T H E  /proc   F I L E S Y S T E M
+------------------------------------------------------------------------------
+/proc/sys         Terrehon Bowden <terrehon@pacbell.net>        October 7 1999
+                  Bodo Bauer <bb@ricochet.net>
+
+2.4.x update	  Jorge Nerin <comandante@zaralinux.com>      November 14 2000
+move /proc/sys	  Shen Feng <shen@cn.fujitsu.com>		  April 1 2009
+------------------------------------------------------------------------------
+Version 1.3                                              Kernel version 2.2.12
+					      Kernel version 2.4.0-test11-pre4
+------------------------------------------------------------------------------
+fixes/update part 1.1  Stefani Seibold <stefani@seibold.net>       June 9 2009
+
+Table of Contents
+-----------------
+
+  0     Preface
+  0.1	Introduction/Credits
+  0.2	Legal Stuff
+
+  1	Collecting System Information
+  1.1	Process-Specific Subdirectories
+  1.2	Kernel data
+  1.3	IDE devices in /proc/ide
+  1.4	Networking info in /proc/net
+  1.5	SCSI info
+  1.6	Parallel port info in /proc/parport
+  1.7	TTY info in /proc/tty
+  1.8	Miscellaneous kernel statistics in /proc/stat
+  1.9 Ext4 file system parameters
+
+  2	Modifying System Parameters
+
+  3	Per-Process Parameters
+  3.1	/proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer
+								score
+  3.2	/proc/<pid>/oom_score - Display current oom-killer score
+  3.3	/proc/<pid>/io - Display the IO accounting fields
+  3.4	/proc/<pid>/coredump_filter - Core dump filtering settings
+  3.5	/proc/<pid>/mountinfo - Information about mounts
+  3.6	/proc/<pid>/comm  & /proc/<pid>/task/<tid>/comm
+
+  4	Configuring procfs
+  4.1	Mount options
+
+------------------------------------------------------------------------------
+Preface
+------------------------------------------------------------------------------
+
+0.1 Introduction/Credits
+------------------------
+
+This documentation is  part of a soon (or  so we hope) to be  released book on
+the SuSE  Linux distribution. As  there is  no complete documentation  for the
+/proc file system and we've used  many freely available sources to write these
+chapters, it  seems only fair  to give the work  back to the  Linux community.
+This work is  based on the 2.2.*  kernel version and the  upcoming 2.4.*. I'm
+afraid it's still far from complete, but we  hope it will be useful. As far as
+we know, it is the first 'all-in-one' document about the /proc file system. It
+is focused  on the Intel  x86 hardware,  so if you  are looking for  PPC, ARM,
+SPARC, AXP, etc., features, you probably  won't find what you are looking for.
+It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
+additions and patches  are welcome and will  be added to this  document if you
+mail them to Bodo.
+
+We'd like  to  thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
+other people for help compiling this documentation. We'd also like to extend a
+special thank  you to Andi Kleen for documentation, which we relied on heavily
+to create  this  document,  as well as the additional information he provided.
+Thanks to  everybody  else  who contributed source or docs to the Linux kernel
+and helped create a great piece of software... :)
+
+If you  have  any comments, corrections or additions, please don't hesitate to
+contact Bodo  Bauer  at  bb@ricochet.net.  We'll  be happy to add them to this
+document.
+
+The   latest   version    of   this   document   is    available   online   at
+http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
+
+If  the above  direction does  not works  for you,  you could  try the  kernel
+mailing  list  at  linux-kernel@vger.kernel.org  and/or try  to  reach  me  at
+comandante@zaralinux.com.
+
+0.2 Legal Stuff
+---------------
+
+We don't  guarantee  the  correctness  of this document, and if you come to us
+complaining about  how  you  screwed  up  your  system  because  of  incorrect
+documentation, we won't feel responsible...
+
+------------------------------------------------------------------------------
+CHAPTER 1: COLLECTING SYSTEM INFORMATION
+------------------------------------------------------------------------------
+
+------------------------------------------------------------------------------
+In This Chapter
+------------------------------------------------------------------------------
+* Investigating  the  properties  of  the  pseudo  file  system  /proc and its
+  ability to provide information on the running Linux system
+* Examining /proc's structure
+* Uncovering  various  information  about the kernel and the processes running
+  on the system
+------------------------------------------------------------------------------
+
+
+The proc  file  system acts as an interface to internal data structures in the
+kernel. It  can  be  used to obtain information about the system and to change
+certain kernel parameters at runtime (sysctl).
+
+First, we'll  take  a  look  at the read-only parts of /proc. In Chapter 2, we
+show you how you can use /proc/sys to change settings.
+
+1.1 Process-Specific Subdirectories
+-----------------------------------
+
+The directory  /proc  contains  (among other things) one subdirectory for each
+process running on the system, which is named after the process ID (PID).
+
+The link  self  points  to  the  process reading the file system. Each process
+subdirectory has the entries listed in Table 1-1.
+
+
+Table 1-1: Process specific entries in /proc
+..............................................................................
+ File		Content
+ clear_refs	Clears page referenced bits shown in smaps output
+ cmdline	Command line arguments
+ cpu		Current and last cpu in which it was executed	(2.4)(smp)
+ cwd		Link to the current working directory
+ environ	Values of environment variables
+ exe		Link to the executable of this process
+ fd		Directory, which contains all file descriptors
+ maps		Memory maps to executables and library files	(2.4)
+ mem		Memory held by this process
+ root		Link to the root directory of this process
+ stat		Process status
+ statm		Process memory status information
+ status		Process status in human readable form
+ wchan		If CONFIG_KALLSYMS is set, a pre-decoded wchan
+ pagemap	Page table
+ stack		Report full stack trace, enable via CONFIG_STACKTRACE
+ smaps		a extension based on maps, showing the memory consumption of
+		each mapping
+..............................................................................
+
+For example, to get the status information of a process, all you have to do is
+read the file /proc/PID/status:
+
+  >cat /proc/self/status
+  Name:   cat
+  State:  R (running)
+  Tgid:   5452
+  Pid:    5452
+  PPid:   743
+  TracerPid:      0						(2.4)
+  Uid:    501     501     501     501
+  Gid:    100     100     100     100
+  FDSize: 256
+  Groups: 100 14 16
+  VmPeak:     5004 kB
+  VmSize:     5004 kB
+  VmLck:         0 kB
+  VmHWM:       476 kB
+  VmRSS:       476 kB
+  VmData:      156 kB
+  VmStk:        88 kB
+  VmExe:        68 kB
+  VmLib:      1412 kB
+  VmPTE:        20 kb
+  VmSwap:        0 kB
+  Threads:        1
+  SigQ:   0/28578
+  SigPnd: 0000000000000000
+  ShdPnd: 0000000000000000
+  SigBlk: 0000000000000000
+  SigIgn: 0000000000000000
+  SigCgt: 0000000000000000
+  CapInh: 00000000fffffeff
+  CapPrm: 0000000000000000
+  CapEff: 0000000000000000
+  CapBnd: ffffffffffffffff
+  voluntary_ctxt_switches:        0
+  nonvoluntary_ctxt_switches:     1
+
+This shows you nearly the same information you would get if you viewed it with
+the ps  command.  In  fact,  ps  uses  the  proc  file  system  to  obtain its
+information.  But you get a more detailed  view of the  process by reading the
+file /proc/PID/status. It fields are described in table 1-2.
+
+The  statm  file  contains  more  detailed  information about the process
+memory usage. Its seven fields are explained in Table 1-3.  The stat file
+contains details information about the process itself.  Its fields are
+explained in Table 1-4.
+
+(for SMP CONFIG users)
+For making accounting scalable, RSS related information are handled in
+asynchronous manner and the vaule may not be very precise. To see a precise
+snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
+It's slow but very precise.
+
+Table 1-2: Contents of the status files (as of 2.6.30-rc7)
+..............................................................................
+ Field                       Content
+ Name                        filename of the executable
+ State                       state (R is running, S is sleeping, D is sleeping
+                             in an uninterruptible wait, Z is zombie,
+			     T is traced or stopped)
+ Tgid                        thread group ID
+ Pid                         process id
+ PPid                        process id of the parent process
+ TracerPid                   PID of process tracing this process (0 if not)
+ Uid                         Real, effective, saved set, and  file system UIDs
+ Gid                         Real, effective, saved set, and  file system GIDs
+ FDSize                      number of file descriptor slots currently allocated
+ Groups                      supplementary group list
+ VmPeak                      peak virtual memory size
+ VmSize                      total program size
+ VmLck                       locked memory size
+ VmHWM                       peak resident set size ("high water mark")
+ VmRSS                       size of memory portions
+ VmData                      size of data, stack, and text segments
+ VmStk                       size of data, stack, and text segments
+ VmExe                       size of text segment
+ VmLib                       size of shared library code
+ VmPTE                       size of page table entries
+ VmSwap                      size of swap usage (the number of referred swapents)
+ Threads                     number of threads
+ SigQ                        number of signals queued/max. number for queue
+ SigPnd                      bitmap of pending signals for the thread
+ ShdPnd                      bitmap of shared pending signals for the process
+ SigBlk                      bitmap of blocked signals
+ SigIgn                      bitmap of ignored signals
+ SigCgt                      bitmap of catched signals
+ CapInh                      bitmap of inheritable capabilities
+ CapPrm                      bitmap of permitted capabilities
+ CapEff                      bitmap of effective capabilities
+ CapBnd                      bitmap of capabilities bounding set
+ Cpus_allowed                mask of CPUs on which this process may run
+ Cpus_allowed_list           Same as previous, but in "list format"
+ Mems_allowed                mask of memory nodes allowed to this process
+ Mems_allowed_list           Same as previous, but in "list format"
+ voluntary_ctxt_switches     number of voluntary context switches
+ nonvoluntary_ctxt_switches  number of non voluntary context switches
+..............................................................................
+
+Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
+..............................................................................
+ Field    Content
+ size     total program size (pages)		(same as VmSize in status)
+ resident size of memory portions (pages)	(same as VmRSS in status)
+ shared   number of pages that are shared	(i.e. backed by a file)
+ trs      number of pages that are 'code'	(not including libs; broken,
+							includes data segment)
+ lrs      number of pages of library		(always 0 on 2.6)
+ drs      number of pages of data/stack		(including libs; broken,
+							includes library text)
+ dt       number of dirty pages			(always 0 on 2.6)
+..............................................................................
+
+
+Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
+..............................................................................
+ Field          Content
+  pid           process id
+  tcomm         filename of the executable
+  state         state (R is running, S is sleeping, D is sleeping in an
+                uninterruptible wait, Z is zombie, T is traced or stopped)
+  ppid          process id of the parent process
+  pgrp          pgrp of the process
+  sid           session id
+  tty_nr        tty the process uses
+  tty_pgrp      pgrp of the tty
+  flags         task flags
+  min_flt       number of minor faults
+  cmin_flt      number of minor faults with child's
+  maj_flt       number of major faults
+  cmaj_flt      number of major faults with child's
+  utime         user mode jiffies
+  stime         kernel mode jiffies
+  cutime        user mode jiffies with child's
+  cstime        kernel mode jiffies with child's
+  priority      priority level
+  nice          nice level
+  num_threads   number of threads
+  it_real_value	(obsolete, always 0)
+  start_time    time the process started after system boot
+  vsize         virtual memory size
+  rss           resident set memory size
+  rsslim        current limit in bytes on the rss
+  start_code    address above which program text can run
+  end_code      address below which program text can run
+  start_stack   address of the start of the main process stack
+  esp           current value of ESP
+  eip           current value of EIP
+  pending       bitmap of pending signals
+  blocked       bitmap of blocked signals
+  sigign        bitmap of ignored signals
+  sigcatch      bitmap of catched signals
+  wchan         address where process went to sleep
+  0             (place holder)
+  0             (place holder)
+  exit_signal   signal to send to parent thread on exit
+  task_cpu      which CPU the task is scheduled on
+  rt_priority   realtime priority
+  policy        scheduling policy (man sched_setscheduler)
+  blkio_ticks   time spent waiting for block IO
+  gtime         guest time of the task in jiffies
+  cgtime        guest time of the task children in jiffies
+  start_data    address above which program data+bss is placed
+  end_data      address below which program data+bss is placed
+  start_brk     address above which program heap can be expanded with brk()
+..............................................................................
+
+The /proc/PID/maps file containing the currently mapped memory regions and
+their access permissions.
+
+The format is:
+
+address           perms offset  dev   inode      pathname
+
+08048000-08049000 r-xp 00000000 03:00 8312       /opt/test
+08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
+0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
+a7cb1000-a7cb2000 ---p 00000000 00:00 0
+a7cb2000-a7eb2000 rw-p 00000000 00:00 0
+a7eb2000-a7eb3000 ---p 00000000 00:00 0
+a7eb3000-a7ed5000 rw-p 00000000 00:00 0          [stack:1001]
+a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
+a8008000-a800a000 r--p 00133000 03:00 4222       /lib/libc.so.6
+a800a000-a800b000 rw-p 00135000 03:00 4222       /lib/libc.so.6
+a800b000-a800e000 rw-p 00000000 00:00 0
+a800e000-a8022000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
+a8022000-a8023000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
+a8023000-a8024000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
+a8024000-a8027000 rw-p 00000000 00:00 0
+a8027000-a8043000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
+a8043000-a8044000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
+a8044000-a8045000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
+aff35000-aff4a000 rw-p 00000000 00:00 0          [stack]
+ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
+
+where "address" is the address space in the process that it occupies, "perms"
+is a set of permissions:
+
+ r = read
+ w = write
+ x = execute
+ s = shared
+ p = private (copy on write)
+
+"offset" is the offset into the mapping, "dev" is the device (major:minor), and
+"inode" is the inode  on that device.  0 indicates that  no inode is associated
+with the memory region, as the case would be with BSS (uninitialized data).
+The "pathname" shows the name associated file for this mapping.  If the mapping
+is not associated with a file:
+
+ [heap]                   = the heap of the program
+ [stack]                  = the stack of the main process
+ [stack:1001]             = the stack of the thread with tid 1001
+ [vdso]                   = the "virtual dynamic shared object",
+                            the kernel system call handler
+
+ or if empty, the mapping is anonymous.
+
+The /proc/PID/task/TID/maps is a view of the virtual memory from the viewpoint
+of the individual tasks of a process. In this file you will see a mapping marked
+as [stack] if that task sees it as a stack. This is a key difference from the
+content of /proc/PID/maps, where you will see all mappings that are being used
+as stack by all of those tasks. Hence, for the example above, the task-level
+map, i.e. /proc/PID/task/TID/maps for thread 1001 will look like this:
+
+08048000-08049000 r-xp 00000000 03:00 8312       /opt/test
+08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
+0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
+a7cb1000-a7cb2000 ---p 00000000 00:00 0
+a7cb2000-a7eb2000 rw-p 00000000 00:00 0
+a7eb2000-a7eb3000 ---p 00000000 00:00 0
+a7eb3000-a7ed5000 rw-p 00000000 00:00 0          [stack]
+a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
+a8008000-a800a000 r--p 00133000 03:00 4222       /lib/libc.so.6
+a800a000-a800b000 rw-p 00135000 03:00 4222       /lib/libc.so.6
+a800b000-a800e000 rw-p 00000000 00:00 0
+a800e000-a8022000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
+a8022000-a8023000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
+a8023000-a8024000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
+a8024000-a8027000 rw-p 00000000 00:00 0
+a8027000-a8043000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
+a8043000-a8044000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
+a8044000-a8045000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
+aff35000-aff4a000 rw-p 00000000 00:00 0
+ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
+
+The /proc/PID/smaps is an extension based on maps, showing the memory
+consumption for each of the process's mappings. For each of mappings there
+is a series of lines such as the following:
+
+08048000-080bc000 r-xp 00000000 03:02 13130      /bin/bash
+Size:               1084 kB
+Rss:                 892 kB
+Pss:                 374 kB
+Shared_Clean:        892 kB
+Shared_Dirty:          0 kB
+Private_Clean:         0 kB
+Private_Dirty:         0 kB
+Referenced:          892 kB
+Anonymous:             0 kB
+Swap:                  0 kB
+KernelPageSize:        4 kB
+MMUPageSize:           4 kB
+Locked:              374 kB
+
+The first of these lines shows the same information as is displayed for the
+mapping in /proc/PID/maps.  The remaining lines show the size of the mapping
+(size), the amount of the mapping that is currently resident in RAM (RSS), the
+process' proportional share of this mapping (PSS), the number of clean and
+dirty private pages in the mapping.  Note that even a page which is part of a
+MAP_SHARED mapping, but has only a single pte mapped, i.e.  is currently used
+by only one process, is accounted as private and not as shared.  "Referenced"
+indicates the amount of memory currently marked as referenced or accessed.
+"Anonymous" shows the amount of memory that does not belong to any file.  Even
+a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
+and a page is modified, the file page is replaced by a private anonymous copy.
+"Swap" shows how much would-be-anonymous memory is also used, but out on
+swap.
+
+This file is only present if the CONFIG_MMU kernel configuration option is
+enabled.
+
+The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
+bits on both physical and virtual pages associated with a process.
+To clear the bits for all the pages associated with the process
+    > echo 1 > /proc/PID/clear_refs
+
+To clear the bits for the anonymous pages associated with the process
+    > echo 2 > /proc/PID/clear_refs
+
+To clear the bits for the file mapped pages associated with the process
+    > echo 3 > /proc/PID/clear_refs
+Any other value written to /proc/PID/clear_refs will have no effect.
+
+The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
+using /proc/kpageflags and number of times a page is mapped using
+/proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt.
+
+1.2 Kernel data
+---------------
+
+Similar to  the  process entries, the kernel data files give information about
+the running kernel. The files used to obtain this information are contained in
+/proc and  are  listed  in Table 1-5. Not all of these will be present in your
+system. It  depends  on the kernel configuration and the loaded modules, which
+files are there, and which are missing.
+
+Table 1-5: Kernel info in /proc
+..............................................................................
+ File        Content                                           
+ apm         Advanced power management info                    
+ buddyinfo   Kernel memory allocator information (see text)	(2.5)
+ bus         Directory containing bus specific information     
+ cmdline     Kernel command line                               
+ cpuinfo     Info about the CPU                                
+ devices     Available devices (block and character)           
+ dma         Used DMS channels                                 
+ filesystems Supported filesystems                             
+ driver	     Various drivers grouped here, currently rtc (2.4)
+ execdomains Execdomains, related to security			(2.4)
+ fb	     Frame Buffer devices				(2.4)
+ fs	     File system parameters, currently nfs/exports	(2.4)
+ ide         Directory containing info about the IDE subsystem 
+ interrupts  Interrupt usage                                   
+ iomem	     Memory map						(2.4)
+ ioports     I/O port usage                                    
+ irq	     Masks for irq to cpu affinity			(2.4)(smp?)
+ isapnp	     ISA PnP (Plug&Play) Info				(2.4)
+ kcore       Kernel core image (can be ELF or A.OUT(deprecated in 2.4))   
+ kmsg        Kernel messages                                   
+ ksyms       Kernel symbol table                               
+ loadavg     Load average of last 1, 5 & 15 minutes                
+ locks       Kernel locks                                      
+ meminfo     Memory info                                       
+ misc        Miscellaneous                                     
+ modules     List of loaded modules                            
+ mounts      Mounted filesystems                               
+ net         Networking info (see text)                        
+ pagetypeinfo Additional page allocator information (see text)  (2.5)
+ partitions  Table of partitions known to the system           
+ pci	     Deprecated info of PCI bus (new way -> /proc/bus/pci/,
+             decoupled by lspci					(2.4)
+ rtc         Real time clock                                   
+ scsi        SCSI info (see text)                              
+ slabinfo    Slab pool info                                    
+ softirqs    softirq usage
+ stat        Overall statistics                                
+ swaps       Swap space utilization                            
+ sys         See chapter 2                                     
+ sysvipc     Info of SysVIPC Resources (msg, sem, shm)		(2.4)
+ tty	     Info of tty drivers
+ uptime      System uptime                                     
+ version     Kernel version                                    
+ video	     bttv info of video resources			(2.4)
+ vmallocinfo Show vmalloced areas
+..............................................................................
+
+You can,  for  example,  check  which interrupts are currently in use and what
+they are used for by looking in the file /proc/interrupts:
+
+  > cat /proc/interrupts 
+             CPU0        
+    0:    8728810          XT-PIC  timer 
+    1:        895          XT-PIC  keyboard 
+    2:          0          XT-PIC  cascade 
+    3:     531695          XT-PIC  aha152x 
+    4:    2014133          XT-PIC  serial 
+    5:      44401          XT-PIC  pcnet_cs 
+    8:          2          XT-PIC  rtc 
+   11:          8          XT-PIC  i82365 
+   12:     182918          XT-PIC  PS/2 Mouse 
+   13:          1          XT-PIC  fpu 
+   14:    1232265          XT-PIC  ide0 
+   15:          7          XT-PIC  ide1 
+  NMI:          0 
+
+In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
+output of a SMP machine):
+
+  > cat /proc/interrupts 
+
+             CPU0       CPU1       
+    0:    1243498    1214548    IO-APIC-edge  timer
+    1:       8949       8958    IO-APIC-edge  keyboard
+    2:          0          0          XT-PIC  cascade
+    5:      11286      10161    IO-APIC-edge  soundblaster
+    8:          1          0    IO-APIC-edge  rtc
+    9:      27422      27407    IO-APIC-edge  3c503
+   12:     113645     113873    IO-APIC-edge  PS/2 Mouse
+   13:          0          0          XT-PIC  fpu
+   14:      22491      24012    IO-APIC-edge  ide0
+   15:       2183       2415    IO-APIC-edge  ide1
+   17:      30564      30414   IO-APIC-level  eth0
+   18:        177        164   IO-APIC-level  bttv
+  NMI:    2457961    2457959 
+  LOC:    2457882    2457881 
+  ERR:       2155
+
+NMI is incremented in this case because every timer interrupt generates a NMI
+(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
+
+LOC is the local interrupt counter of the internal APIC of every CPU.
+
+ERR is incremented in the case of errors in the IO-APIC bus (the bus that
+connects the CPUs in a SMP system. This means that an error has been detected,
+the IO-APIC automatically retry the transmission, so it should not be a big
+problem, but you should read the SMP-FAQ.
+
+In 2.6.2* /proc/interrupts was expanded again.  This time the goal was for
+/proc/interrupts to display every IRQ vector in use by the system, not
+just those considered 'most important'.  The new vectors are:
+
+  THR -- interrupt raised when a machine check threshold counter
+  (typically counting ECC corrected errors of memory or cache) exceeds
+  a configurable threshold.  Only available on some systems.
+
+  TRM -- a thermal event interrupt occurs when a temperature threshold
+  has been exceeded for the CPU.  This interrupt may also be generated
+  when the temperature drops back to normal.
+
+  SPU -- a spurious interrupt is some interrupt that was raised then lowered
+  by some IO device before it could be fully processed by the APIC.  Hence
+  the APIC sees the interrupt but does not know what device it came from.
+  For this case the APIC will generate the interrupt with a IRQ vector
+  of 0xff. This might also be generated by chipset bugs.
+
+  RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
+  sent from one CPU to another per the needs of the OS.  Typically,
+  their statistics are used by kernel developers and interested users to
+  determine the occurrence of interrupts of the given type.
+
+The above IRQ vectors are displayed only when relevant.  For example,
+the threshold vector does not exist on x86_64 platforms.  Others are
+suppressed when the system is a uniprocessor.  As of this writing, only
+i386 and x86_64 platforms support the new IRQ vector displays.
+
+Of some interest is the introduction of the /proc/irq directory to 2.4.
+It could be used to set IRQ to CPU affinity, this means that you can "hook" an
+IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
+irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
+prof_cpu_mask.
+
+For example 
+  > ls /proc/irq/
+  0  10  12  14  16  18  2  4  6  8  prof_cpu_mask
+  1  11  13  15  17  19  3  5  7  9  default_smp_affinity
+  > ls /proc/irq/0/
+  smp_affinity
+
+smp_affinity is a bitmask, in which you can specify which CPUs can handle the
+IRQ, you can set it by doing:
+
+  > echo 1 > /proc/irq/10/smp_affinity
+
+This means that only the first CPU will handle the IRQ, but you can also echo
+5 which means that only the first and fourth CPU can handle the IRQ.
+
+The contents of each smp_affinity file is the same by default:
+
+  > cat /proc/irq/0/smp_affinity
+  ffffffff
+
+There is an alternate interface, smp_affinity_list which allows specifying
+a cpu range instead of a bitmask:
+
+  > cat /proc/irq/0/smp_affinity_list
+  1024-1031
+
+The default_smp_affinity mask applies to all non-active IRQs, which are the
+IRQs which have not yet been allocated/activated, and hence which lack a
+/proc/irq/[0-9]* directory.
+
+The node file on an SMP system shows the node to which the device using the IRQ
+reports itself as being attached. This hardware locality information does not
+include information about any possible driver locality preference.
+
+prof_cpu_mask specifies which CPUs are to be profiled by the system wide
+profiler. Default value is ffffffff (all cpus if there are only 32 of them).
+
+The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
+between all the CPUs which are allowed to handle it. As usual the kernel has
+more info than you and does a better job than you, so the defaults are the
+best choice for almost everyone.  [Note this applies only to those IO-APIC's
+that support "Round Robin" interrupt distribution.]
+
+There are  three  more  important subdirectories in /proc: net, scsi, and sys.
+The general  rule  is  that  the  contents,  or  even  the  existence of these
+directories, depend  on your kernel configuration. If SCSI is not enabled, the
+directory scsi  may  not  exist. The same is true with the net, which is there
+only when networking support is present in the running kernel.
+
+The slabinfo  file  gives  information  about  memory usage at the slab level.
+Linux uses  slab  pools for memory management above page level in version 2.2.
+Commonly used  objects  have  their  own  slab  pool (such as network buffers,
+directory cache, and so on).
+
+..............................................................................
+
+> cat /proc/buddyinfo
+
+Node 0, zone      DMA      0      4      5      4      4      3 ...
+Node 0, zone   Normal      1      0      0      1    101      8 ...
+Node 0, zone  HighMem      2      0      0      1      1      0 ...
+
+External fragmentation is a problem under some workloads, and buddyinfo is a
+useful tool for helping diagnose these problems.  Buddyinfo will give you a 
+clue as to how big an area you can safely allocate, or why a previous
+allocation failed.
+
+Each column represents the number of pages of a certain order which are 
+available.  In this case, there are 0 chunks of 2^0*PAGE_SIZE available in 
+ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE 
+available in ZONE_NORMAL, etc... 
+
+More information relevant to external fragmentation can be found in
+pagetypeinfo.
+
+> cat /proc/pagetypeinfo
+Page block order: 9
+Pages per block:  512
+
+Free pages count per migrate type at order       0      1      2      3      4      5      6      7      8      9     10
+Node    0, zone      DMA, type    Unmovable      0      0      0      1      1      1      1      1      1      1      0
+Node    0, zone      DMA, type  Reclaimable      0      0      0      0      0      0      0      0      0      0      0
+Node    0, zone      DMA, type      Movable      1      1      2      1      2      1      1      0      1      0      2
+Node    0, zone      DMA, type      Reserve      0      0      0      0      0      0      0      0      0      1      0
+Node    0, zone      DMA, type      Isolate      0      0      0      0      0      0      0      0      0      0      0
+Node    0, zone    DMA32, type    Unmovable    103     54     77      1      1      1     11      8      7      1      9
+Node    0, zone    DMA32, type  Reclaimable      0      0      2      1      0      0      0      0      1      0      0
+Node    0, zone    DMA32, type      Movable    169    152    113     91     77     54     39     13      6      1    452
+Node    0, zone    DMA32, type      Reserve      1      2      2      2      2      0      1      1      1      1      0
+Node    0, zone    DMA32, type      Isolate      0      0      0      0      0      0      0      0      0      0      0
+
+Number of blocks type     Unmovable  Reclaimable      Movable      Reserve      Isolate
+Node 0, zone      DMA            2            0            5            1            0
+Node 0, zone    DMA32           41            6          967            2            0
+
+Fragmentation avoidance in the kernel works by grouping pages of different
+migrate types into the same contiguous regions of memory called page blocks.
+A page block is typically the size of the default hugepage size e.g. 2MB on
+X86-64. By keeping pages grouped based on their ability to move, the kernel
+can reclaim pages within a page block to satisfy a high-order allocation.
+
+The pagetypinfo begins with information on the size of a page block. It
+then gives the same type of information as buddyinfo except broken down
+by migrate-type and finishes with details on how many page blocks of each
+type exist.
+
+If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
+from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can
+make an estimate of the likely number of huge pages that can be allocated
+at a given point in time. All the "Movable" blocks should be allocatable
+unless memory has been mlock()'d. Some of the Reclaimable blocks should
+also be allocatable although a lot of filesystem metadata may have to be
+reclaimed to achieve this.
+
+..............................................................................
+
+meminfo:
+
+Provides information about distribution and utilization of memory.  This
+varies by architecture and compile options.  The following is from a
+16GB PIII, which has highmem enabled.  You may not have all of these fields.
+
+> cat /proc/meminfo
+
+The "Locked" indicates whether the mapping is locked in memory or not.
+
+
+MemTotal:     16344972 kB
+MemFree:      13634064 kB
+Buffers:          3656 kB
+Cached:        1195708 kB
+SwapCached:          0 kB
+Active:         891636 kB
+Inactive:      1077224 kB
+HighTotal:    15597528 kB
+HighFree:     13629632 kB
+LowTotal:       747444 kB
+LowFree:          4432 kB
+SwapTotal:           0 kB
+SwapFree:            0 kB
+Dirty:             968 kB
+Writeback:           0 kB
+AnonPages:      861800 kB
+Mapped:         280372 kB
+Slab:           284364 kB
+SReclaimable:   159856 kB
+SUnreclaim:     124508 kB
+PageTables:      24448 kB
+NFS_Unstable:        0 kB
+Bounce:              0 kB
+WritebackTmp:        0 kB
+CommitLimit:   7669796 kB
+Committed_AS:   100056 kB
+VmallocTotal:   112216 kB
+VmallocUsed:       428 kB
+VmallocChunk:   111088 kB
+
+    MemTotal: Total usable ram (i.e. physical ram minus a few reserved
+              bits and the kernel binary code)
+     MemFree: The sum of LowFree+HighFree
+     Buffers: Relatively temporary storage for raw disk blocks
+              shouldn't get tremendously large (20MB or so)
+      Cached: in-memory cache for files read from the disk (the
+              pagecache).  Doesn't include SwapCached
+  SwapCached: Memory that once was swapped out, is swapped back in but
+              still also is in the swapfile (if memory is needed it
+              doesn't need to be swapped out AGAIN because it is already
+              in the swapfile. This saves I/O)
+      Active: Memory that has been used more recently and usually not
+              reclaimed unless absolutely necessary.
+    Inactive: Memory which has been less recently used.  It is more
+              eligible to be reclaimed for other purposes
+   HighTotal:
+    HighFree: Highmem is all memory above ~860MB of physical memory
+              Highmem areas are for use by userspace programs, or
+              for the pagecache.  The kernel must use tricks to access
+              this memory, making it slower to access than lowmem.
+    LowTotal:
+     LowFree: Lowmem is memory which can be used for everything that
+              highmem can be used for, but it is also available for the
+              kernel's use for its own data structures.  Among many
+              other things, it is where everything from the Slab is
+              allocated.  Bad things happen when you're out of lowmem.
+   SwapTotal: total amount of swap space available
+    SwapFree: Memory which has been evicted from RAM, and is temporarily
+              on the disk
+       Dirty: Memory which is waiting to get written back to the disk
+   Writeback: Memory which is actively being written back to the disk
+   AnonPages: Non-file backed pages mapped into userspace page tables
+      Mapped: files which have been mmaped, such as libraries
+        Slab: in-kernel data structures cache
+SReclaimable: Part of Slab, that might be reclaimed, such as caches
+  SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
+  PageTables: amount of memory dedicated to the lowest level of page
+              tables.
+NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
+	      storage
+      Bounce: Memory used for block device "bounce buffers"
+WritebackTmp: Memory used by FUSE for temporary writeback buffers
+ CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
+              this is the total amount of  memory currently available to
+              be allocated on the system. This limit is only adhered to
+              if strict overcommit accounting is enabled (mode 2 in
+              'vm.overcommit_memory').
+              The CommitLimit is calculated with the following formula:
+              CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap
+              For example, on a system with 1G of physical RAM and 7G
+              of swap with a `vm.overcommit_ratio` of 30 it would
+              yield a CommitLimit of 7.3G.
+              For more details, see the memory overcommit documentation
+              in vm/overcommit-accounting.
+Committed_AS: The amount of memory presently allocated on the system.
+              The committed memory is a sum of all of the memory which
+              has been allocated by processes, even if it has not been
+              "used" by them as of yet. A process which malloc()'s 1G
+              of memory, but only touches 300M of it will only show up
+              as using 300M of memory even if it has the address space
+              allocated for the entire 1G. This 1G is memory which has
+              been "committed" to by the VM and can be used at any time
+              by the allocating application. With strict overcommit
+              enabled on the system (mode 2 in 'vm.overcommit_memory'),
+              allocations which would exceed the CommitLimit (detailed
+              above) will not be permitted. This is useful if one needs
+              to guarantee that processes will not fail due to lack of
+              memory once that memory has been successfully allocated.
+VmallocTotal: total size of vmalloc memory area
+ VmallocUsed: amount of vmalloc area which is used
+VmallocChunk: largest contiguous block of vmalloc area which is free
+
+..............................................................................
+
+vmallocinfo:
+
+Provides information about vmalloced/vmaped areas. One line per area,
+containing the virtual address range of the area, size in bytes,
+caller information of the creator, and optional information depending
+on the kind of area :
+
+ pages=nr    number of pages
+ phys=addr   if a physical address was specified
+ ioremap     I/O mapping (ioremap() and friends)
+ vmalloc     vmalloc() area
+ vmap        vmap()ed pages
+ user        VM_USERMAP area
+ vpages      buffer for pages pointers was vmalloced (huge area)
+ N<node>=nr  (Only on NUMA kernels)
+             Number of pages allocated on memory node <node>
+
+> cat /proc/vmallocinfo
+0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
+  /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
+0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
+  /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
+0xffffc20000302000-0xffffc20000304000    8192 acpi_tb_verify_table+0x21/0x4f...
+  phys=7fee8000 ioremap
+0xffffc20000304000-0xffffc20000307000   12288 acpi_tb_verify_table+0x21/0x4f...
+  phys=7fee7000 ioremap
+0xffffc2000031d000-0xffffc2000031f000    8192 init_vdso_vars+0x112/0x210
+0xffffc2000031f000-0xffffc2000032b000   49152 cramfs_uncompress_init+0x2e ...
+  /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
+0xffffc2000033a000-0xffffc2000033d000   12288 sys_swapon+0x640/0xac0      ...
+  pages=2 vmalloc N1=2
+0xffffc20000347000-0xffffc2000034c000   20480 xt_alloc_table_info+0xfe ...
+  /0x130 [x_tables] pages=4 vmalloc N0=4
+0xffffffffa0000000-0xffffffffa000f000   61440 sys_init_module+0xc27/0x1d00 ...
+   pages=14 vmalloc N2=14
+0xffffffffa000f000-0xffffffffa0014000   20480 sys_init_module+0xc27/0x1d00 ...
+   pages=4 vmalloc N1=4
+0xffffffffa0014000-0xffffffffa0017000   12288 sys_init_module+0xc27/0x1d00 ...
+   pages=2 vmalloc N1=2
+0xffffffffa0017000-0xffffffffa0022000   45056 sys_init_module+0xc27/0x1d00 ...
+   pages=10 vmalloc N0=10
+
+..............................................................................
+
+softirqs:
+
+Provides counts of softirq handlers serviced since boot time, for each cpu.
+
+> cat /proc/softirqs
+                CPU0       CPU1       CPU2       CPU3
+      HI:          0          0          0          0
+   TIMER:      27166      27120      27097      27034
+  NET_TX:          0          0          0         17
+  NET_RX:         42          0          0         39
+   BLOCK:          0          0        107       1121
+ TASKLET:          0          0          0        290
+   SCHED:      27035      26983      26971      26746
+ HRTIMER:          0          0          0          0
+     RCU:       1678       1769       2178       2250
+
+
+1.3 IDE devices in /proc/ide
+----------------------------
+
+The subdirectory /proc/ide contains information about all IDE devices of which
+the kernel  is  aware.  There is one subdirectory for each IDE controller, the
+file drivers  and a link for each IDE device, pointing to the device directory
+in the controller specific subtree.
+
+The file  drivers  contains general information about the drivers used for the
+IDE devices:
+
+  > cat /proc/ide/drivers
+  ide-cdrom version 4.53
+  ide-disk version 1.08
+
+More detailed  information  can  be  found  in  the  controller  specific
+subdirectories. These  are  named  ide0,  ide1  and  so  on.  Each  of  these
+directories contains the files shown in table 1-6.
+
+
+Table 1-6: IDE controller info in  /proc/ide/ide?
+..............................................................................
+ File    Content                                 
+ channel IDE channel (0 or 1)                    
+ config  Configuration (only for PCI/IDE bridge) 
+ mate    Mate name                               
+ model   Type/Chipset of IDE controller          
+..............................................................................
+
+Each device  connected  to  a  controller  has  a separate subdirectory in the
+controllers directory.  The  files  listed in table 1-7 are contained in these
+directories.
+
+
+Table 1-7: IDE device information
+..............................................................................
+ File             Content                                    
+ cache            The cache                                  
+ capacity         Capacity of the medium (in 512Byte blocks) 
+ driver           driver and version                         
+ geometry         physical and logical geometry              
+ identify         device identify block                      
+ media            media type                                 
+ model            device identifier                          
+ settings         device setup                               
+ smart_thresholds IDE disk management thresholds             
+ smart_values     IDE disk management values                 
+..............................................................................
+
+The most  interesting  file is settings. This file contains a nice overview of
+the drive parameters:
+
+  # cat /proc/ide/ide0/hda/settings 
+  name                    value           min             max             mode 
+  ----                    -----           ---             ---             ---- 
+  bios_cyl                526             0               65535           rw 
+  bios_head               255             0               255             rw 
+  bios_sect               63              0               63              rw 
+  breada_readahead        4               0               127             rw 
+  bswap                   0               0               1               r 
+  file_readahead          72              0               2097151         rw 
+  io_32bit                0               0               3               rw 
+  keepsettings            0               0               1               rw 
+  max_kb_per_request      122             1               127             rw 
+  multcount               0               0               8               rw 
+  nice1                   1               0               1               rw 
+  nowerr                  0               0               1               rw 
+  pio_mode                write-only      0               255             w 
+  slow                    0               0               1               rw 
+  unmaskirq               0               0               1               rw 
+  using_dma               0               0               1               rw 
+
+
+1.4 Networking info in /proc/net
+--------------------------------
+
+The subdirectory  /proc/net  follows  the  usual  pattern. Table 1-8 shows the
+additional values  you  get  for  IP  version 6 if you configure the kernel to
+support this. Table 1-9 lists the files and their meaning.
+
+
+Table 1-8: IPv6 info in /proc/net
+..............................................................................
+ File       Content                                               
+ udp6       UDP sockets (IPv6)                                    
+ tcp6       TCP sockets (IPv6)                                    
+ raw6       Raw device statistics (IPv6)                          
+ igmp6      IP multicast addresses, which this host joined (IPv6) 
+ if_inet6   List of IPv6 interface addresses                      
+ ipv6_route Kernel routing table for IPv6                         
+ rt6_stats  Global IPv6 routing tables statistics                 
+ sockstat6  Socket statistics (IPv6)                              
+ snmp6      Snmp data (IPv6)                                      
+..............................................................................
+
+
+Table 1-9: Network info in /proc/net
+..............................................................................
+ File          Content                                                         
+ arp           Kernel  ARP table                                               
+ dev           network devices with statistics                                 
+ dev_mcast     the Layer2 multicast groups a device is listening too
+               (interface index, label, number of references, number of bound
+               addresses). 
+ dev_stat      network device status                                           
+ ip_fwchains   Firewall chain linkage                                          
+ ip_fwnames    Firewall chain names                                            
+ ip_masq       Directory containing the masquerading tables                    
+ ip_masquerade Major masquerading table                                        
+ netstat       Network statistics                                              
+ raw           raw device statistics                                           
+ route         Kernel routing table                                            
+ rpc           Directory containing rpc info                                   
+ rt_cache      Routing cache                                                   
+ snmp          SNMP data                                                       
+ sockstat      Socket statistics                                               
+ tcp           TCP  sockets                                                    
+ tr_rif        Token ring RIF routing table                                    
+ udp           UDP sockets                                                     
+ unix          UNIX domain sockets                                             
+ wireless      Wireless interface data (Wavelan etc)                           
+ igmp          IP multicast addresses, which this host joined                  
+ psched        Global packet scheduler parameters.                             
+ netlink       List of PF_NETLINK sockets                                      
+ ip_mr_vifs    List of multicast virtual interfaces                            
+ ip_mr_cache   List of multicast routing cache                                 
+..............................................................................
+
+You can  use  this  information  to see which network devices are available in
+your system and how much traffic was routed over those devices:
+
+  > cat /proc/net/dev 
+  Inter-|Receive                                                   |[... 
+   face |bytes    packets errs drop fifo frame compressed multicast|[... 
+      lo:  908188   5596     0    0    0     0          0         0 [...         
+    ppp0:15475140  20721   410    0    0   410          0         0 [...  
+    eth0:  614530   7085     0    0    0     0          0         1 [... 
+   
+  ...] Transmit 
+  ...] bytes    packets errs drop fifo colls carrier compressed 
+  ...]  908188     5596    0    0    0     0       0          0 
+  ...] 1375103    17405    0    0    0     0       0          0 
+  ...] 1703981     5535    0    0    0     3       0          0 
+
+In addition, each Channel Bond interface has its own directory.  For
+example, the bond0 device will have a directory called /proc/net/bond0/.
+It will contain information that is specific to that bond, such as the
+current slaves of the bond, the link status of the slaves, and how
+many times the slaves link has failed.
+
+1.5 SCSI info
+-------------
+
+If you  have  a  SCSI  host adapter in your system, you'll find a subdirectory
+named after  the driver for this adapter in /proc/scsi. You'll also see a list
+of all recognized SCSI devices in /proc/scsi:
+
+  >cat /proc/scsi/scsi 
+  Attached devices: 
+  Host: scsi0 Channel: 00 Id: 00 Lun: 00 
+    Vendor: IBM      Model: DGHS09U          Rev: 03E0 
+    Type:   Direct-Access                    ANSI SCSI revision: 03 
+  Host: scsi0 Channel: 00 Id: 06 Lun: 00 
+    Vendor: PIONEER  Model: CD-ROM DR-U06S   Rev: 1.04 
+    Type:   CD-ROM                           ANSI SCSI revision: 02 
+
+
+The directory  named  after  the driver has one file for each adapter found in
+the system.  These  files  contain information about the controller, including
+the used  IRQ  and  the  IO  address range. The amount of information shown is
+dependent on  the adapter you use. The example shows the output for an Adaptec
+AHA-2940 SCSI adapter:
+
+  > cat /proc/scsi/aic7xxx/0 
+   
+  Adaptec AIC7xxx driver version: 5.1.19/3.2.4 
+  Compile Options: 
+    TCQ Enabled By Default : Disabled 
+    AIC7XXX_PROC_STATS     : Disabled 
+    AIC7XXX_RESET_DELAY    : 5 
+  Adapter Configuration: 
+             SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 
+                             Ultra Wide Controller 
+      PCI MMAPed I/O Base: 0xeb001000 
+   Adapter SEEPROM Config: SEEPROM found and used. 
+        Adaptec SCSI BIOS: Enabled 
+                      IRQ: 10 
+                     SCBs: Active 0, Max Active 2, 
+                           Allocated 15, HW 16, Page 255 
+               Interrupts: 160328 
+        BIOS Control Word: 0x18b6 
+     Adapter Control Word: 0x005b 
+     Extended Translation: Enabled 
+  Disconnect Enable Flags: 0xffff 
+       Ultra Enable Flags: 0x0001 
+   Tag Queue Enable Flags: 0x0000 
+  Ordered Queue Tag Flags: 0x0000 
+  Default Tag Queue Depth: 8 
+      Tagged Queue By Device array for aic7xxx host instance 0: 
+        {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 
+      Actual queue depth per device for aic7xxx host instance 0: 
+        {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 
+  Statistics: 
+  (scsi0:0:0:0) 
+    Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 
+    Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 
+    Total transfers 160151 (74577 reads and 85574 writes) 
+  (scsi0:0:6:0) 
+    Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 
+    Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 
+    Total transfers 0 (0 reads and 0 writes) 
+
+
+1.6 Parallel port info in /proc/parport
+---------------------------------------
+
+The directory  /proc/parport  contains information about the parallel ports of
+your system.  It  has  one  subdirectory  for  each port, named after the port
+number (0,1,2,...).
+
+These directories contain the four files shown in Table 1-10.
+
+
+Table 1-10: Files in /proc/parport
+..............................................................................
+ File      Content                                                             
+ autoprobe Any IEEE-1284 device ID information that has been acquired.         
+ devices   list of the device drivers using that port. A + will appear by the
+           name of the device currently using the port (it might not appear
+           against any). 
+ hardware  Parallel port's base address, IRQ line and DMA channel.             
+ irq       IRQ that parport is using for that port. This is in a separate
+           file to allow you to alter it by writing a new value in (IRQ
+           number or none). 
+..............................................................................
+
+1.7 TTY info in /proc/tty
+-------------------------
+
+Information about  the  available  and actually used tty's can be found in the
+directory /proc/tty.You'll  find  entries  for drivers and line disciplines in
+this directory, as shown in Table 1-11.
+
+
+Table 1-11: Files in /proc/tty
+..............................................................................
+ File          Content                                        
+ drivers       list of drivers and their usage                
+ ldiscs        registered line disciplines                    
+ driver/serial usage statistic and status of single tty lines 
+..............................................................................
+
+To see  which  tty's  are  currently in use, you can simply look into the file
+/proc/tty/drivers:
+
+  > cat /proc/tty/drivers 
+  pty_slave            /dev/pts      136   0-255 pty:slave 
+  pty_master           /dev/ptm      128   0-255 pty:master 
+  pty_slave            /dev/ttyp       3   0-255 pty:slave 
+  pty_master           /dev/pty        2   0-255 pty:master 
+  serial               /dev/cua        5   64-67 serial:callout 
+  serial               /dev/ttyS       4   64-67 serial 
+  /dev/tty0            /dev/tty0       4       0 system:vtmaster 
+  /dev/ptmx            /dev/ptmx       5       2 system 
+  /dev/console         /dev/console    5       1 system:console 
+  /dev/tty             /dev/tty        5       0 system:/dev/tty 
+  unknown              /dev/tty        4    1-63 console 
+
+
+1.8 Miscellaneous kernel statistics in /proc/stat
+-------------------------------------------------
+
+Various pieces   of  information about  kernel activity  are  available in the
+/proc/stat file.  All  of  the numbers reported  in  this file are  aggregates
+since the system first booted.  For a quick look, simply cat the file:
+
+  > cat /proc/stat
+  cpu  2255 34 2290 22625563 6290 127 456 0 0
+  cpu0 1132 34 1441 11311718 3675 127 438 0 0
+  cpu1 1123 0 849 11313845 2614 0 18 0 0
+  intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
+  ctxt 1990473
+  btime 1062191376
+  processes 2915
+  procs_running 1
+  procs_blocked 0
+  softirq 183433 0 21755 12 39 1137 231 21459 2263
+
+The very first  "cpu" line aggregates the  numbers in all  of the other "cpuN"
+lines.  These numbers identify the amount of time the CPU has spent performing
+different kinds of work.  Time units are in USER_HZ (typically hundredths of a
+second).  The meanings of the columns are as follows, from left to right:
+
+- user: normal processes executing in user mode
+- nice: niced processes executing in user mode
+- system: processes executing in kernel mode
+- idle: twiddling thumbs
+- iowait: waiting for I/O to complete
+- irq: servicing interrupts
+- softirq: servicing softirqs
+- steal: involuntary wait
+- guest: running a normal guest
+- guest_nice: running a niced guest
+
+The "intr" line gives counts of interrupts  serviced since boot time, for each
+of the  possible system interrupts.   The first  column  is the  total of  all
+interrupts serviced; each  subsequent column is the  total for that particular
+interrupt.
+
+The "ctxt" line gives the total number of context switches across all CPUs.
+
+The "btime" line gives  the time at which the  system booted, in seconds since
+the Unix epoch.
+
+The "processes" line gives the number  of processes and threads created, which
+includes (but  is not limited  to) those  created by  calls to the  fork() and
+clone() system calls.
+
+The "procs_running" line gives the total number of threads that are
+running or ready to run (i.e., the total number of runnable threads).
+
+The   "procs_blocked" line gives  the  number of  processes currently blocked,
+waiting for I/O to complete.
+
+The "softirq" line gives counts of softirqs serviced since boot time, for each
+of the possible system softirqs. The first column is the total of all
+softirqs serviced; each subsequent column is the total for that particular
+softirq.
+
+
+1.9 Ext4 file system parameters
+------------------------------
+
+Information about mounted ext4 file systems can be found in
+/proc/fs/ext4.  Each mounted filesystem will have a directory in
+/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
+/proc/fs/ext4/dm-0).   The files in each per-device directory are shown
+in Table 1-12, below.
+
+Table 1-12: Files in /proc/fs/ext4/<devname>
+..............................................................................
+ File            Content                                        
+ mb_groups       details of multiblock allocator buddy cache of free blocks
+..............................................................................
+
+2.0 /proc/consoles
+------------------
+Shows registered system console lines.
+
+To see which character device lines are currently used for the system console
+/dev/console, you may simply look into the file /proc/consoles:
+
+  > cat /proc/consoles
+  tty0                 -WU (ECp)       4:7
+  ttyS0                -W- (Ep)        4:64
+
+The columns are:
+
+  device               name of the device
+  operations           R = can do read operations
+                       W = can do write operations
+                       U = can do unblank
+  flags                E = it is enabled
+                       C = it is preferred console
+                       B = it is primary boot console
+                       p = it is used for printk buffer
+                       b = it is not a TTY but a Braille device
+                       a = it is safe to use when cpu is offline
+  major:minor          major and minor number of the device separated by a colon
+
+------------------------------------------------------------------------------
+Summary
+------------------------------------------------------------------------------
+The /proc file system serves information about the running system. It not only
+allows access to process data but also allows you to request the kernel status
+by reading files in the hierarchy.
+
+The directory  structure  of /proc reflects the types of information and makes
+it easy, if not obvious, where to look for specific data.
+------------------------------------------------------------------------------
+
+------------------------------------------------------------------------------
+CHAPTER 2: MODIFYING SYSTEM PARAMETERS
+------------------------------------------------------------------------------
+
+------------------------------------------------------------------------------
+In This Chapter
+------------------------------------------------------------------------------
+* Modifying kernel parameters by writing into files found in /proc/sys
+* Exploring the files which modify certain parameters
+* Review of the /proc/sys file tree
+------------------------------------------------------------------------------
+
+
+A very  interesting part of /proc is the directory /proc/sys. This is not only
+a source  of  information,  it also allows you to change parameters within the
+kernel. Be  very  careful  when attempting this. You can optimize your system,
+but you  can  also  cause  it  to  crash.  Never  alter kernel parameters on a
+production system.  Set  up  a  development machine and test to make sure that
+everything works  the  way  you want it to. You may have no alternative but to
+reboot the machine once an error has been made.
+
+To change  a  value,  simply  echo  the new value into the file. An example is
+given below  in the section on the file system data. You need to be root to do
+this. You  can  create  your  own  boot script to perform this every time your
+system boots.
+
+The files  in /proc/sys can be used to fine tune and monitor miscellaneous and
+general things  in  the operation of the Linux kernel. Since some of the files
+can inadvertently  disrupt  your  system,  it  is  advisable  to  read  both
+documentation and  source  before actually making adjustments. In any case, be
+very careful  when  writing  to  any  of these files. The entries in /proc may
+change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
+review the kernel documentation in the directory /usr/src/linux/Documentation.
+This chapter  is  heavily  based  on the documentation included in the pre 2.2
+kernels, and became part of it in version 2.2.1 of the Linux kernel.
+
+Please see: Documentation/sysctl/ directory for descriptions of these
+entries.
+
+------------------------------------------------------------------------------
+Summary
+------------------------------------------------------------------------------
+Certain aspects  of  kernel  behavior  can be modified at runtime, without the
+need to  recompile  the kernel, or even to reboot the system. The files in the
+/proc/sys tree  can  not only be read, but also modified. You can use the echo
+command to write value into these files, thereby changing the default settings
+of the kernel.
+------------------------------------------------------------------------------
+
+------------------------------------------------------------------------------
+CHAPTER 3: PER-PROCESS PARAMETERS
+------------------------------------------------------------------------------
+
+3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
+--------------------------------------------------------------------------------
+
+These file can be used to adjust the badness heuristic used to select which
+process gets killed in out of memory conditions.
+
+The badness heuristic assigns a value to each candidate task ranging from 0
+(never kill) to 1000 (always kill) to determine which process is targeted.  The
+units are roughly a proportion along that range of allowed memory the process
+may allocate from based on an estimation of its current memory and swap use.
+For example, if a task is using all allowed memory, its badness score will be
+1000.  If it is using half of its allowed memory, its score will be 500.
+
+There is an additional factor included in the badness score: root
+processes are given 3% extra memory over other tasks.
+
+The amount of "allowed" memory depends on the context in which the oom killer
+was called.  If it is due to the memory assigned to the allocating task's cpuset
+being exhausted, the allowed memory represents the set of mems assigned to that
+cpuset.  If it is due to a mempolicy's node(s) being exhausted, the allowed
+memory represents the set of mempolicy nodes.  If it is due to a memory
+limit (or swap limit) being reached, the allowed memory is that configured
+limit.  Finally, if it is due to the entire system being out of memory, the
+allowed memory represents all allocatable resources.
+
+The value of /proc/<pid>/oom_score_adj is added to the badness score before it
+is used to determine which task to kill.  Acceptable values range from -1000
+(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX).  This allows userspace to
+polarize the preference for oom killing either by always preferring a certain
+task or completely disabling it.  The lowest possible value, -1000, is
+equivalent to disabling oom killing entirely for that task since it will always
+report a badness score of 0.
+
+Consequently, it is very simple for userspace to define the amount of memory to
+consider for each task.  Setting a /proc/<pid>/oom_score_adj value of +500, for
+example, is roughly equivalent to allowing the remainder of tasks sharing the
+same system, cpuset, mempolicy, or memory controller resources to use at least
+50% more memory.  A value of -500, on the other hand, would be roughly
+equivalent to discounting 50% of the task's allowed memory from being considered
+as scoring against the task.
+
+For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
+be used to tune the badness score.  Its acceptable values range from -16
+(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
+(OOM_DISABLE) to disable oom killing entirely for that task.  Its value is
+scaled linearly with /proc/<pid>/oom_score_adj.
+
+Writing to /proc/<pid>/oom_score_adj or /proc/<pid>/oom_adj will change the
+other with its scaled value.
+
+The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
+value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
+requires CAP_SYS_RESOURCE.
+
+NOTICE: /proc/<pid>/oom_adj is deprecated and will be removed, please see
+Documentation/feature-removal-schedule.txt.
+
+Caveat: when a parent task is selected, the oom killer will sacrifice any first
+generation children with separate address spaces instead, if possible.  This
+avoids servers and important system daemons from being killed and loses the
+minimal amount of work.
+
+
+3.2 /proc/<pid>/oom_score - Display current oom-killer score
+-------------------------------------------------------------
+
+This file can be used to check the current score used by the oom-killer is for
+any given <pid>. Use it together with /proc/<pid>/oom_adj to tune which
+process should be killed in an out-of-memory situation.
+
+
+3.3  /proc/<pid>/io - Display the IO accounting fields
+-------------------------------------------------------
+
+This file contains IO statistics for each running process
+
+Example
+-------
+
+test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
+[1] 3828
+
+test:/tmp # cat /proc/3828/io
+rchar: 323934931
+wchar: 323929600
+syscr: 632687
+syscw: 632675
+read_bytes: 0
+write_bytes: 323932160
+cancelled_write_bytes: 0
+
+
+Description
+-----------
+
+rchar
+-----
+
+I/O counter: chars read
+The number of bytes which this task has caused to be read from storage. This
+is simply the sum of bytes which this process passed to read() and pread().
+It includes things like tty IO and it is unaffected by whether or not actual
+physical disk IO was required (the read might have been satisfied from
+pagecache)
+
+
+wchar
+-----
+
+I/O counter: chars written
+The number of bytes which this task has caused, or shall cause to be written
+to disk. Similar caveats apply here as with rchar.
+
+
+syscr
+-----
+
+I/O counter: read syscalls
+Attempt to count the number of read I/O operations, i.e. syscalls like read()
+and pread().
+
+
+syscw
+-----
+
+I/O counter: write syscalls
+Attempt to count the number of write I/O operations, i.e. syscalls like
+write() and pwrite().
+
+
+read_bytes
+----------
+
+I/O counter: bytes read
+Attempt to count the number of bytes which this process really did cause to
+be fetched from the storage layer. Done at the submit_bio() level, so it is
+accurate for block-backed filesystems. <please add status regarding NFS and
+CIFS at a later time>
+
+
+write_bytes
+-----------
+
+I/O counter: bytes written
+Attempt to count the number of bytes which this process caused to be sent to
+the storage layer. This is done at page-dirtying time.
+
+
+cancelled_write_bytes
+---------------------
+
+The big inaccuracy here is truncate. If a process writes 1MB to a file and
+then deletes the file, it will in fact perform no writeout. But it will have
+been accounted as having caused 1MB of write.
+In other words: The number of bytes which this process caused to not happen,
+by truncating pagecache. A task can cause "negative" IO too. If this task
+truncates some dirty pagecache, some IO which another task has been accounted
+for (in its write_bytes) will not be happening. We _could_ just subtract that
+from the truncating task's write_bytes, but there is information loss in doing
+that.
+
+
+Note
+----
+
+At its current implementation state, this is a bit racy on 32-bit machines: if
+process A reads process B's /proc/pid/io while process B is updating one of
+those 64-bit counters, process A could see an intermediate result.
+
+
+More information about this can be found within the taskstats documentation in
+Documentation/accounting.
+
+3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
+---------------------------------------------------------------
+When a process is dumped, all anonymous memory is written to a core file as
+long as the size of the core file isn't limited. But sometimes we don't want
+to dump some memory segments, for example, huge shared memory. Conversely,
+sometimes we want to save file-backed memory segments into a core file, not
+only the individual files.
+
+/proc/<pid>/coredump_filter allows you to customize which memory segments
+will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
+of memory types. If a bit of the bitmask is set, memory segments of the
+corresponding memory type are dumped, otherwise they are not dumped.
+
+The following 7 memory types are supported:
+  - (bit 0) anonymous private memory
+  - (bit 1) anonymous shared memory
+  - (bit 2) file-backed private memory
+  - (bit 3) file-backed shared memory
+  - (bit 4) ELF header pages in file-backed private memory areas (it is
+            effective only if the bit 2 is cleared)
+  - (bit 5) hugetlb private memory
+  - (bit 6) hugetlb shared memory
+
+  Note that MMIO pages such as frame buffer are never dumped and vDSO pages
+  are always dumped regardless of the bitmask status.
+
+  Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
+  effected by bit 5-6.
+
+Default value of coredump_filter is 0x23; this means all anonymous memory
+segments and hugetlb private memory are dumped.
+
+If you don't want to dump all shared memory segments attached to pid 1234,
+write 0x21 to the process's proc file.
+
+  $ echo 0x21 > /proc/1234/coredump_filter
+
+When a new process is created, the process inherits the bitmask status from its
+parent. It is useful to set up coredump_filter before the program runs.
+For example:
+
+  $ echo 0x7 > /proc/self/coredump_filter
+  $ ./some_program
+
+3.5	/proc/<pid>/mountinfo - Information about mounts
+--------------------------------------------------------
+
+This file contains lines of the form:
+
+36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
+(1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)
+
+(1) mount ID:  unique identifier of the mount (may be reused after umount)
+(2) parent ID:  ID of parent (or of self for the top of the mount tree)
+(3) major:minor:  value of st_dev for files on filesystem
+(4) root:  root of the mount within the filesystem
+(5) mount point:  mount point relative to the process's root
+(6) mount options:  per mount options
+(7) optional fields:  zero or more fields of the form "tag[:value]"
+(8) separator:  marks the end of the optional fields
+(9) filesystem type:  name of filesystem of the form "type[.subtype]"
+(10) mount source:  filesystem specific information or "none"
+(11) super options:  per super block options
+
+Parsers should ignore all unrecognised optional fields.  Currently the
+possible optional fields are:
+
+shared:X  mount is shared in peer group X
+master:X  mount is slave to peer group X
+propagate_from:X  mount is slave and receives propagation from peer group X (*)
+unbindable  mount is unbindable
+
+(*) X is the closest dominant peer group under the process's root.  If
+X is the immediate master of the mount, or if there's no dominant peer
+group under the same root, then only the "master:X" field is present
+and not the "propagate_from:X" field.
+
+For more information on mount propagation see:
+
+  Documentation/filesystems/sharedsubtree.txt
+
+
+3.6	/proc/<pid>/comm  & /proc/<pid>/task/<tid>/comm
+--------------------------------------------------------
+These files provide a method to access a tasks comm value. It also allows for
+a task to set its own or one of its thread siblings comm value. The comm value
+is limited in size compared to the cmdline value, so writing anything longer
+then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
+comm value.
+
+
+------------------------------------------------------------------------------
+Configuring procfs
+------------------------------------------------------------------------------
+
+4.1	Mount options
+---------------------
+
+The following mount options are supported:
+
+	hidepid=	Set /proc/<pid>/ access mode.
+	gid=		Set the group authorized to learn processes information.
+
+hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
+(default).
+
+hidepid=1 means users may not access any /proc/<pid>/ directories but their
+own.  Sensitive files like cmdline, sched*, status are now protected against
+other users.  This makes it impossible to learn whether any user runs
+specific program (given the program doesn't reveal itself by its behaviour).
+As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
+poorly written programs passing sensitive information via program arguments are
+now protected against local eavesdroppers.
+
+hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
+users.  It doesn't mean that it hides a fact whether a process with a specific
+pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
+but it hides process' uid and gid, which may be learned by stat()'ing
+/proc/<pid>/ otherwise.  It greatly complicates an intruder's task of gathering
+information about running processes, whether some daemon runs with elevated
+privileges, whether other user runs some sensitive program, whether other users
+run any program at all, etc.
+
+gid= defines a group authorized to learn processes information otherwise
+prohibited by hidepid=.  If you use some daemon like identd which needs to learn
+information about processes information, just add identd to this group.