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authorLinus Torvalds <torvalds@linux-foundation.org>2013-07-02 19:53:30 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-07-02 19:53:30 -0700
commitf317ff9eed763e99bd226a447f93d42509434f43 (patch)
treed77edfcdb1e7c32c30327f50dce04bcff8ec1531 /Documentation/kernel-parameters.txt
parent13cc56013842a847a0f6ff805d9ed9181e753ef8 (diff)
parenta85f1a41f020bc2c97611060bcfae6f48a1db28d (diff)
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op-kernel-dev-f317ff9eed763e99bd226a447f93d42509434f43.tar.gz
Merge branch 'for-3.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq
Pull workqueue changes from Tejun Heo: "Surprisingly, Lai and I didn't break too many things implementing custom pools and stuff last time around and there aren't any follow-up changes necessary at this point. The only change in this pull request is Viresh's patches to make some per-cpu workqueues to behave as unbound workqueues dependent on a boot param whose default can be configured via a config option. This leads to higher processing overhead / lower bandwidth as more work items are bounced across CPUs; however, it can lead to noticeable powersave in certain configurations - ~10% w/ idlish constant workload on a big.LITTLE configuration according to Viresh. This is because per-cpu workqueues interfere with how the scheduler perceives whether or not each CPU is idle by forcing pinned tasks on them, which makes the scheduler's power-aware scheduling decisions less effective. Its effectiveness is likely less pronounced on homogenous configurations and this type of optimization can probably be made automatic; however, the changes are pretty minimal and the affected workqueues are clearly marked, so it's an easy gain for some configurations for the time being with pretty unintrusive changes." * 'for-3.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq: fbcon: queue work on power efficient wq block: queue work on power efficient wq PHYLIB: queue work on system_power_efficient_wq workqueue: Add system wide power_efficient workqueues workqueues: Introduce new flag WQ_POWER_EFFICIENT for power oriented workqueues
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diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
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--- a/Documentation/kernel-parameters.txt
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@@ -3341,6 +3341,21 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
that this also can be controlled per-workqueue for
workqueues visible under /sys/bus/workqueue/.
+ workqueue.power_efficient
+ Per-cpu workqueues are generally preferred because
+ they show better performance thanks to cache
+ locality; unfortunately, per-cpu workqueues tend to
+ be more power hungry than unbound workqueues.
+
+ Enabling this makes the per-cpu workqueues which
+ were observed to contribute significantly to power
+ consumption unbound, leading to measurably lower
+ power usage at the cost of small performance
+ overhead.
+
+ The default value of this parameter is determined by
+ the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
+
x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
default x2apic cluster mode on platforms
supporting x2apic.
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