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authorViresh Kumar <viresh.kumar@linaro.org>2013-04-08 16:45:40 +0530
committerTejun Heo <tj@kernel.org>2013-05-14 10:50:06 -0700
commitcee22a15052faa817e3ec8985a28154d3fabc7aa (patch)
tree506028de7bd3bf7de08a7933b5601355f27c5262 /kernel/power
parentf722406faae2d073cc1d01063d1123c35425939e (diff)
workqueues: Introduce new flag WQ_POWER_EFFICIENT for power oriented workqueues
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>
Diffstat (limited to 'kernel/power')
-rw-r--r--kernel/power/Kconfig20
1 files changed, 20 insertions, 0 deletions
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 5dfdc9ea180b..46455961a88f 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -263,6 +263,26 @@ 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