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Groups > linux.kernel > #1667131
| From | "Luis R. Rodriguez" <mcgrof@kernel.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [RFC v2 1/2] swait: add idle variants which don't contribute to load average |
| Date | 2017-06-15 20:50 +0200 |
| Message-ID | <tSI0a-63s-5@gated-at.bofh.it> (permalink) |
| References | <tSGrn-5cj-11@gated-at.bofh.it> <tSI0a-63s-7@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
There are cases where folks are using an interruptible swait when
using kthreads. This is rather confusing given you'd expect
interruptible waits to be -- interruptible, but kthreads are not
interruptible ! The reason for such practice though is to avoid
having these kthreads contribute to the system load average.
When systems are idle some kthreads may spend a lot of time blocking if
using swait_event_timeout(). This would contribute to the system load
average. On systems without preemption this would mean the load average
of an idle system is bumped to 2 instead of 0. On systems with PREEMPT=y
this would mean the load average of an idle system is bumped to 3
instead of 0.
This adds proper API using TASK_IDLE to make such goals explicit and
avoid confusion.
Suggested-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
---
include/linux/swait.h | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/include/linux/swait.h b/include/linux/swait.h
index 2c700694d50a..105c70e23286 100644
--- a/include/linux/swait.h
+++ b/include/linux/swait.h
@@ -194,4 +194,29 @@ do { \
__ret; \
})
+#define __swait_event_idle(wq, condition) \
+ ___swait_event(wq, condition, TASK_IDLE, 0, schedule())
+
+#define swait_event_idle(wq, condition) \
+({ \
+ int __ret = 0; \
+ if (!(condition)) \
+ __ret = __swait_event_idle(wq, condition); \
+ __ret; \
+})
+
+#define __swait_event_idle_timeout(wq, condition, timeout) \
+ ___swait_event(wq, ___wait_cond_timeout(condition), \
+ TASK_IDLE, timeout, \
+ __ret = schedule_timeout(__ret))
+
+#define swait_event_idle_timeout(wq, condition, timeout) \
+({ \
+ long __ret = timeout; \
+ if (!___wait_cond_timeout(condition)) \
+ __ret = __swait_event_idle_timeout(wq, \
+ condition, timeout); \
+ __ret; \
+})
+
#endif /* _LINUX_SWAIT_H */
--
2.11.0
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[RFC] rcu: use killable versions of swait "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-06-15 01:10 +0200
Re: [RFC] rcu: use killable versions of swait "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-15 01:50 +0200
Re: [RFC] rcu: use killable versions of swait "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-06-15 18:00 +0200
Re: [RFC] rcu: use killable versions of swait "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-15 18:30 +0200
Re: [RFC] rcu: use killable versions of swait "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-06-15 18:40 +0200
Re: [RFC] rcu: use killable versions of swait ebiederm@xmission.com (Eric W. Biederman) - 2017-06-15 19:10 +0200
[RFC v2 0/2] swait: add idle to make idle-hacks on kthreads explicit "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-06-15 20:50 +0200
[RFC v2 1/2] swait: add idle variants which don't contribute to load average "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-06-15 20:50 +0200
Re: [RFC v2 1/2] swait: add idle variants which don't contribute to load average Boqun Feng <boqun.feng@gmail.com> - 2017-06-16 02:50 +0200
Re: [RFC v2 1/2] swait: add idle variants which don't contribute to load average ebiederm@xmission.com (Eric W. Biederman) - 2017-06-16 22:40 +0200
Re: [RFC v2 1/2] swait: add idle variants which don't contribute to load average "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-19 20:00 +0200
[RFC v2 2/2] rcu: use idle versions of swait to make idle-hack clear "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-06-15 20:50 +0200
Re: [RFC v2 0/2] swait: add idle to make idle-hacks on kthreads explicit "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-16 00:00 +0200
Re: [RFC v2 0/2] swait: add idle to make idle-hacks on kthreads explicit "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-06-16 01:30 +0200
Re: [RFC v2 0/2] swait: add idle to make idle-hacks on kthreads explicit "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-16 01:50 +0200
Re: [RFC v2 0/2] swait: add idle to make idle-hacks on kthreads explicit ebiederm@xmission.com (Eric W. Biederman) - 2017-06-16 22:50 +0200
Re: [RFC v2 0/2] swait: add idle to make idle-hacks on kthreads explicit "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-19 20:00 +0200
Re: [RFC] rcu: use killable versions of swait "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-15 19:40 +0200
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