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>

1 files changed, 4 insertions, 0 deletions

diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index 906cae771585..059431ed67db 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -196,6 +196,8 @@ static int fill_pid(pid_t pid, struct task_struct *tsk,
 
         /* fill in basic acct fields */
         stats->version = TASKSTATS_VERSION;
+        stats->nvcsw = tsk->nvcsw;
+        stats->nivcsw = tsk->nivcsw;
         bacct_add_tsk(stats, tsk);
 
         /* fill in extended acct fields */
@@ -242,6 +244,8 @@ static int fill_tgid(pid_t tgid, struct task_struct *first,
                  */
                 delayacct_add_tsk(stats, tsk);
 
+                stats->nvcsw += tsk->nvcsw;
+                stats->nivcsw += tsk->nivcsw;
         } while_each_thread(first, tsk);
 
         unlock_task_sighand(first, &flags);