* [PATCH v2] sched/wait: use freezable_schedule when possible
@ 2019-02-07 20:03 Hugo Lefeuvre
2019-02-08 0:12 ` Joel Fernandes
2019-02-11 10:53 ` [tip:sched/core] sched/wait: Use freezable_schedule() " tip-bot for Hugo Lefeuvre
0 siblings, 2 replies; 3+ messages in thread
From: Hugo Lefeuvre @ 2019-02-07 20:03 UTC (permalink / raw)
To: Joel Fernandes
Cc: Ingo Molnar, Peter Zijlstra, linux-kernel, Rafael J. Wysocki
Replace schedule(); try_to_freeze() by 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>
---
Changes in v2:
- Add test results to commit message.
- Split from initial patch set[0] since this patch can go in separately
[0] https://lkml.org/lkml/2019/2/1/19
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) \
({ \
--
2.20.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] sched/wait: use freezable_schedule when possible
2019-02-07 20:03 [PATCH v2] sched/wait: use freezable_schedule when possible Hugo Lefeuvre
@ 2019-02-08 0:12 ` Joel Fernandes
2019-02-11 10:53 ` [tip:sched/core] sched/wait: Use freezable_schedule() " tip-bot for Hugo Lefeuvre
1 sibling, 0 replies; 3+ messages in thread
From: Joel Fernandes @ 2019-02-08 0:12 UTC (permalink / raw)
To: Hugo Lefeuvre
Cc: Ingo Molnar, Peter Zijlstra, linux-kernel, Rafael J. Wysocki
On Thu, Feb 07, 2019 at 09:03:52PM +0100, Hugo Lefeuvre wrote:
> Replace schedule(); try_to_freeze() by 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.
>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> Signed-off-by: Hugo Lefeuvre <hle@owl.eu.com>
> ---
> Changes in v2:
> - Add test results to commit message.
> - Split from initial patch set[0] since this patch can go in separately
> [0] https://lkml.org/lkml/2019/2/1/19
>
> 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) \
> ({ \
> --
> 2.20.1
^ permalink raw reply [flat|nested] 3+ messages in thread
* [tip:sched/core] sched/wait: Use freezable_schedule() when possible
2019-02-07 20:03 [PATCH v2] sched/wait: use freezable_schedule when possible Hugo Lefeuvre
2019-02-08 0:12 ` Joel Fernandes
@ 2019-02-11 10:53 ` tip-bot for Hugo Lefeuvre
1 sibling, 0 replies; 3+ messages in thread
From: tip-bot for Hugo Lefeuvre @ 2019-02-11 10:53 UTC (permalink / raw)
To: linux-tip-commits
Cc: torvalds, hpa, linux-kernel, tglx, joel, hle, rjw, peterz, mingo
Commit-ID: 2b9c2a4859ad5ac7b5a28e9db28c3e618760fe8c
Gitweb: https://git.kernel.org/tip/2b9c2a4859ad5ac7b5a28e9db28c3e618760fe8c
Author: Hugo Lefeuvre <hle@owl.eu.com>
AuthorDate: Thu, 7 Feb 2019 21:03:52 +0100
Committer: Ingo Molnar <mingo@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 <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>
---
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) \
({ \
^ permalink raw reply related [flat|nested] 3+ messages in thread
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2019-02-08 0:12 ` Joel Fernandes
2019-02-11 10:53 ` [tip:sched/core] sched/wait: Use freezable_schedule() " tip-bot for Hugo Lefeuvre
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