taskstats: add context-switch counters
Make available to the user the following task and process performance
statistics:
* Involuntary Context Switches (task_struct->nivcsw)
* Voluntary Context Switches (task_struct->nvcsw)
Statistics information is available from:
1. taskstats interface (Documentation/accounting/)
2. /proc/PID/status (task only).
This data is useful for detecting hyperactivity patterns between processes.
[akpm@linux-foundation.org: cleanup]
Signed-off-by: Maxim Uvarov <muvarov@ru.mvista.com>
Cc: Shailabh Nagar <nagar@watson.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Jay Lan <jlan@engr.sgi.com>
Cc: Jonathan Lim <jlim@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/accounting/taskstats-struct.txt b/Documentation/accounting/taskstats-struct.txt
index 661c797..8aa7529 100644
--- a/Documentation/accounting/taskstats-struct.txt
+++ b/Documentation/accounting/taskstats-struct.txt
@@ -22,6 +22,8 @@
/* Extended accounting fields end */
Their values are collected if CONFIG_TASK_XACCT is set.
+4) Per-task and per-thread context switch count statistics
+
Future extension should add fields to the end of the taskstats struct, and
should not change the relative position of each field within the struct.
@@ -158,4 +160,8 @@
/* Extended accounting fields end */
+4) Per-task and per-thread statistics
+ __u64 nvcsw; /* Context voluntary switch counter */
+ __u64 nivcsw; /* Context involuntary switch counter */
+
}
