workqueues: Introduce new flag WQ_POWER_EFFICIENT for power oriented …

…workqueues
Adapted for 3.4 from lsk-v3.10

Workqueues can be performance or power-oriented. Currently, most workqueues are
bound to the CPU they were created on. This gives good performance (due to cache
effects) at the cost of potentially waking up otherwise idle cores (Idle from
scheduler's perspective. Which may or may not be physically idle) just to
process some work. To save power, we can allow the work to be rescheduled on a
core that is already awake.

Workqueues created with the WQ_UNBOUND flag will allow some power savings.
However, we don't change the default behaviour of the system.  To enable
power-saving behaviour, a new config option CONFIG_WQ_POWER_EFFICIENT needs to
be turned on. This option can also be overridden by the
workqueue.power_efficient boot parameter.

tj: Updated config description and comments.  Renamed
    CONFIG_WQ_POWER_EFFICIENT to CONFIG_WQ_POWER_EFFICIENT_DEFAULT.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
(cherry picked from commit cee22a1)
Signed-off-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Luis Cruz <ljc2491@gmail.com>

Signed-off-by: GuneetAtwal <harjinder767@gmail.com>
 workqueue: Add system wide power_efficient workqueues
Adapted for 3.4 from lsk-v3.10

This patch adds system wide workqueues aligned towards power saving. This is
done by allocating them with WQ_UNBOUND flag if 'wq_power_efficient' is set to
'true'.

tj: updated comments a bit.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
(cherry picked from commit 0668106)
Signed-off-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Luis Cruz <ljc2491@gmail.com>

Signed-off-by: GuneetAtwal <harjinder767@gmail.com>
 block: queue work on power efficient wq
Adapted for 3.4 from lsk-v3.10

Block layer uses workqueues for multiple purposes. There is no real dependency
of scheduling these on the cpu which scheduled them.

On a idle system, it is observed that and idle cpu wakes up many times just to
service this work. It would be better if we can schedule it on a cpu which the
scheduler believes to be the most appropriate one.

This patch replaces normal workqueues with power efficient versions.

Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
(cherry picked from commit 695588f)
Signed-off-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Luis Cruz <ljc2491@gmail.com>
Signed-off-by: poondog <markj338@gmail.com>

Signed-off-by: GuneetAtwal <harjinder767@gmail.com>
  PHYLIB: queue work on system_power_efficient_wq
Adapted for 3.4 from lsk-v3.10

Phylib uses workqueues for multiple purposes. There is no real dependency of
scheduling these on the cpu which scheduled them.

On a idle system, it is observed that and idle cpu wakes up many times just to
service this work. It would be better if we can schedule it on a cpu which the
scheduler believes to be the most appropriate one.

This patch replaces system_wq with system_power_efficient_wq for PHYLIB.

Cc: David S. Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Tejun Heo <tj@kernel.org>
(cherry picked from commit bbb47bd)
Signed-off-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Luis Cruz <ljc2491@gmail.com>
Signed-off-by: poondog <markj338@gmail.com>

Signed-off-by: GuneetAtwal <harjinder767@gmail.com>
  ASoC: pcm: Use the power efficient workqueue for delayed powerdown
Adapted for 3.4 from lsk-v3.10

There is no need to use a normal per-CPU workqueue for delayed power downs
as they're not timing or performance critical and waking up a core for them
would defeat some of the point.

Signed-off-by: Mark Brown <broonie@linaro.org>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
(cherry picked from commit d4e1a73)
Signed-off-by: Luis Cruz <ljc2491@gmail.com>
Signed-off-by: poondog <markj338@gmail.com>

Signed-off-by: GuneetAtwal <harjinder767@gmail.com>