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author | Linus Torvalds <torvalds@linux-foundation.org> | 2013-07-03 02:53:30 (GMT) |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-07-03 02:53:30 (GMT) |
commit | f317ff9eed763e99bd226a447f93d42509434f43 (patch) | |
tree | d77edfcdb1e7c32c30327f50dce04bcff8ec1531 /Documentation/kernel-parameters.txt | |
parent | 13cc56013842a847a0f6ff805d9ed9181e753ef8 (diff) | |
parent | a85f1a41f020bc2c97611060bcfae6f48a1db28d (diff) | |
download | linux-f317ff9eed763e99bd226a447f93d42509434f43.tar.xz |
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
Diffstat (limited to 'Documentation/kernel-parameters.txt')
-rw-r--r-- | Documentation/kernel-parameters.txt | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 2fe6e76..81732b8 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -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. |