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

1 files changed, 15 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 2fe6e767b3d6..81732b8abd3a 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.