dirty fix to merging

1 files changed, 97 insertions, 0 deletions

diff --git a/include/linux/dynamic_queue_limits.h b/include/linux/dynamic_queue_limits.h
new file mode 100644
index 00000000..5621547d
--- /dev/null
+++ b/include/linux/dynamic_queue_limits.h
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+/*
+ * Dynamic queue limits (dql) - Definitions
+ *
+ * Copyright (c) 2011, Tom Herbert <therbert@google.com>
+ *
+ * This header file contains the definitions for dynamic queue limits (dql).
+ * dql would be used in conjunction with a producer/consumer type queue
+ * (possibly a HW queue).  Such a queue would have these general properties:
+ *
+ *   1) Objects are queued up to some limit specified as number of objects.
+ *   2) Periodically a completion process executes which retires consumed
+ *      objects.
+ *   3) Starvation occurs when limit has been reached, all queued data has
+ *      actually been consumed, but completion processing has not yet run
+ *      so queuing new data is blocked.
+ *   4) Minimizing the amount of queued data is desirable.
+ *
+ * The goal of dql is to calculate the limit as the minimum number of objects
+ * needed to prevent starvation.
+ *
+ * The primary functions of dql are:
+ *    dql_queued - called when objects are enqueued to record number of objects
+ *    dql_avail - returns how many objects are available to be queued based
+ *      on the object limit and how many objects are already enqueued
+ *    dql_completed - called at completion time to indicate how many objects
+ *      were retired from the queue
+ *
+ * The dql implementation does not implement any locking for the dql data
+ * structures, the higher layer should provide this.  dql_queued should
+ * be serialized to prevent concurrent execution of the function; this
+ * is also true for  dql_completed.  However, dql_queued and dlq_completed  can
+ * be executed concurrently (i.e. they can be protected by different locks).
+ */
+
+#ifndef _LINUX_DQL_H
+#define _LINUX_DQL_H
+
+#ifdef __KERNEL__
+
+struct dql {
+	/* Fields accessed in enqueue path (dql_queued) */
+	unsigned int	num_queued;		/* Total ever queued */
+	unsigned int	adj_limit;		/* limit + num_completed */
+	unsigned int	last_obj_cnt;		/* Count at last queuing */
+
+	/* Fields accessed only by completion path (dql_completed) */
+
+	unsigned int	limit ____cacheline_aligned_in_smp; /* Current limit */
+	unsigned int	num_completed;		/* Total ever completed */
+
+	unsigned int	prev_ovlimit;		/* Previous over limit */
+	unsigned int	prev_num_queued;	/* Previous queue total */
+	unsigned int	prev_last_obj_cnt;	/* Previous queuing cnt */
+
+	unsigned int	lowest_slack;		/* Lowest slack found */
+	unsigned long	slack_start_time;	/* Time slacks seen */
+
+	/* Configuration */
+	unsigned int	max_limit;		/* Max limit */
+	unsigned int	min_limit;		/* Minimum limit */
+	unsigned int	slack_hold_time;	/* Time to measure slack */
+};
+
+/* Set some static maximums */
+#define DQL_MAX_OBJECT (UINT_MAX / 16)
+#define DQL_MAX_LIMIT ((UINT_MAX / 2) - DQL_MAX_OBJECT)
+
+/*
+ * Record number of objects queued. Assumes that caller has already checked
+ * availability in the queue with dql_avail.
+ */
+static inline void dql_queued(struct dql *dql, unsigned int count)
+{
+	BUG_ON(count > DQL_MAX_OBJECT);
+
+	dql->num_queued += count;
+	dql->last_obj_cnt = count;
+}
+
+/* Returns how many objects can be queued, < 0 indicates over limit. */
+static inline int dql_avail(const struct dql *dql)
+{
+	return dql->adj_limit - dql->num_queued;
+}
+
+/* Record number of completed objects and recalculate the limit. */
+void dql_completed(struct dql *dql, unsigned int count);
+
+/* Reset dql state */
+void dql_reset(struct dql *dql);
+
+/* Initialize dql state */
+int dql_init(struct dql *dql, unsigned hold_time);
+
+#endif /* _KERNEL_ */
+
+#endif /* _LINUX_DQL_H */