From d5c373eb5610686162ff50429f63f4c00c554799 Mon Sep 17 00:00:00 2001 From: Jason Low Date: Wed, 14 Oct 2015 12:07:55 -0700 Subject: posix_cpu_timer: Convert cputimer->running to bool In the next patch in this series, a new field 'checking_timer' will be added to 'struct thread_group_cputimer'. Both this and the existing 'running' integer field are just used as boolean values. To save space in the structure, we can make both of these fields booleans. This is a preparatory patch to convert the existing running integer field to a boolean. Suggested-by: George Spelvin Signed-off-by: Jason Low Reviewed: George Spelvin Cc: Oleg Nesterov Cc: Paul E. McKenney Cc: Frederic Weisbecker Cc: Davidlohr Bueso Cc: Steven Rostedt Cc: hideaki.kimura@hpe.com Cc: terry.rudd@hpe.com Cc: scott.norton@hpe.com Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1444849677-29330-4-git-send-email-jason.low2@hp.com Signed-off-by: Thomas Gleixner --- include/linux/init_task.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/init_task.h') diff --git a/include/linux/init_task.h b/include/linux/init_task.h index e38681f4912d..c43b80f3f875 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -59,7 +59,7 @@ extern struct fs_struct init_fs; .rlim = INIT_RLIMITS, \ .cputimer = { \ .cputime_atomic = INIT_CPUTIME_ATOMIC, \ - .running = 0, \ + .running = false, \ }, \ INIT_PREV_CPUTIME(sig) \ .cred_guard_mutex = \ -- cgit v1.2.3 From c8d75aa47dd585c9538a8205e9bb9847e12cfb84 Mon Sep 17 00:00:00 2001 From: Jason Low Date: Wed, 14 Oct 2015 12:07:56 -0700 Subject: posix_cpu_timer: Reduce unnecessary sighand lock contention It was found while running a database workload on large systems that significant time was spent trying to acquire the sighand lock. The issue was that whenever an itimer expired, many threads ended up simultaneously trying to send the signal. Most of the time, nothing happened after acquiring the sighand lock because another thread had just already sent the signal and updated the "next expire" time. The fastpath_timer_check() didn't help much since the "next expire" time was updated after the threads exit fastpath_timer_check(). This patch addresses this by having the thread_group_cputimer structure maintain a boolean to signify when a thread in the group is already checking for process wide timers, and adds extra logic in the fastpath to check the boolean. Signed-off-by: Jason Low Reviewed-by: Oleg Nesterov Reviewed-by: George Spelvin Cc: Paul E. McKenney Cc: Frederic Weisbecker Cc: Davidlohr Bueso Cc: Steven Rostedt Cc: hideaki.kimura@hpe.com Cc: terry.rudd@hpe.com Cc: scott.norton@hpe.com Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1444849677-29330-5-git-send-email-jason.low2@hp.com Signed-off-by: Thomas Gleixner --- include/linux/init_task.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/init_task.h') diff --git a/include/linux/init_task.h b/include/linux/init_task.h index c43b80f3f875..810a34f60424 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -60,6 +60,7 @@ extern struct fs_struct init_fs; .cputimer = { \ .cputime_atomic = INIT_CPUTIME_ATOMIC, \ .running = false, \ + .checking_timer = false, \ }, \ INIT_PREV_CPUTIME(sig) \ .cred_guard_mutex = \ -- cgit v1.2.3