Commit-ID: 2b9c2a4859ad5ac7b5a28e9db28c3e618760fe8c Gitweb: https://git.kernel.org/tip/2b9c2a4859ad5ac7b5a28e9db28c3e618760fe8c Author: Hugo Lefeuvre <h...@owl.eu.com> AuthorDate: Thu, 7 Feb 2019 21:03:52 +0100 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Mon, 11 Feb 2019 08:34:04 +0100
sched/wait: Use freezable_schedule() when possible Replace 'schedule(); try_to_freeze();' with a call to freezable_schedule(). Tasks calling freezable_schedule() set the PF_FREEZER_SKIP flag before calling schedule(). Unlike tasks calling schedule(); try_to_freeze() tasks calling freezable_schedule() are not awaken by try_to_freeze_tasks(). Instead they call try_to_freeze() when they wake up if the freeze is still underway. It is not a problem since sleeping tasks can't do anything which isn't allowed for a frozen task while sleeping. The result is a potential performance gain during freeze, since less tasks have to be awaken. For instance on a bare Debian vm running a 4.19 stable kernel, the number of tasks skipped in freeze_task() went up from 12 without the patch to 32 with the patch (out of 448), an increase of > x2.5. Signed-off-by: Hugo Lefeuvre <h...@owl.eu.com> Reviewed-by: Joel Fernandes (Google) <j...@joelfernandes.org> Cc: Joel Fernandes <j...@joelfernandes.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Rafael J. Wysocki <r...@rjwysocki.net> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/20190207200352.ga27...@behemoth.owl.eu.com.local Signed-off-by: Ingo Molnar <mi...@kernel.org> --- include/linux/wait.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/include/linux/wait.h b/include/linux/wait.h index ed7c122cb31f..5f3efabc36f4 100644 --- a/include/linux/wait.h +++ b/include/linux/wait.h @@ -308,7 +308,7 @@ do { \ #define __wait_event_freezable(wq_head, condition) \ ___wait_event(wq_head, condition, TASK_INTERRUPTIBLE, 0, 0, \ - schedule(); try_to_freeze()) + freezable_schedule()) /** * wait_event_freezable - sleep (or freeze) until a condition gets true @@ -367,7 +367,7 @@ do { \ #define __wait_event_freezable_timeout(wq_head, condition, timeout) \ ___wait_event(wq_head, ___wait_cond_timeout(condition), \ TASK_INTERRUPTIBLE, 0, timeout, \ - __ret = schedule_timeout(__ret); try_to_freeze()) + __ret = freezable_schedule_timeout(__ret)) /* * like wait_event_timeout() -- except it uses TASK_INTERRUPTIBLE to avoid @@ -588,7 +588,7 @@ do { \ #define __wait_event_freezable_exclusive(wq, condition) \ ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 1, 0, \ - schedule(); try_to_freeze()) + freezable_schedule()) #define wait_event_freezable_exclusive(wq, condition) \ ({ \
