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Merge branch 'for-3.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq

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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
This commit is contained in:
Linus Torvalds
2013-07-02 19:53:30 -07:00
parent 13cc560138 a85f1a41f0
commit f317ff9eed
9 changed files with 113 additions and 12 deletions
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20
kernel/power/Kconfig
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@@ -262,6 +262,26 @@ config PM_GENERIC_DOMAINS
bool
depends on PM
config WQ_POWER_EFFICIENT_DEFAULT
bool "Enable workqueue power-efficient mode by default"
depends on PM
default n
help
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 workqueue.power_efficient kernel parameter 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.
This config option determines whether workqueue.power_efficient
is enabled by default.
If in doubt, say N.
config PM_GENERIC_DOMAINS_SLEEP
def_bool y
depends on PM_SLEEP && PM_GENERIC_DOMAINS