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 <hle@owl.eu.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20190207200352.GA27859@behemoth.owl.eu.com.local
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/include/linux/wait.h b/include/linux/wait.h
index ed7c122..5f3efab 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -308,7 +308,7 @@
#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 @@
#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 @@
#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) \
({ \
