This patchset was called: "Create sched_select_cpu() and use it for workqueues" for the first three versions. Earlier discussions over v3, v2 and v1 can be found here: https://lkml.org/lkml/2013/3/18/364 http://lists.linaro.org/pipermail/linaro-dev/2012-November/014344.html http://www.mail-archive.com/linaro-dev@xxxxxxxxxxxxxxxx/msg13342.html V4 is here: https://lkml.org/lkml/2013/3/31/55 Workqueues can be performance or power oriented. For performance we may want to keep them running on a single cpu, so that it remains cache hot. For power we can give scheduler the liberty to choose target cpu for running work handler. Later one (Power oriented WQ) can be achieved if the workqueue is allocated with WQ_UNBOUND flag. Enabling CONFIG_WQ_POWER_EFFICIENT will set 'wq_power_efficient' to 'true'. Setting 'power_efficient' boot param will override value of 'wq_power_efficient' variable. When 'wq_power_efficient' is set to 'true', we will convert WQ_POWER_EFFICIENT flag to WQ_UNBOUND on wq allocation. And so scheduler will have the liberty to choose where to run this work. Here we are migrating few users of workqueues to WQ_POWER_EFFICIENT. These drivers are found to be very much active on idle or lightly busy system and using WQ_POWER_EFFICIENT for these gave impressive results. These would be used in power saving mode only if relevant configs are enabled at compile time or in bootargs. Otherwise behavior is unchanged. Setup: ----- - ARM Vexpress TC2 - big.LITTLE CPU - Core 0-1: A15, 2-4: A7 - rootfs: linaro-ubuntu-devel This patchset has been tested on a big LITTLE system (heterogeneous) but is useful for all other homogeneous systems as well. During these tests audio was played in background using aplay. Results: ------- Cluster A15 Energy Cluster A7 Energy Total ------------------------- ----------------------- ------ Without this patchset (Energy in Joules): --------------------------------------------------- 0.151162 2.183545 2.334707 0.223730 2.687067 2.910797 0.289687 2.732702 3.022389 0.454198 2.745908 3.200106 0.495552 2.746465 3.242017 Average: 0.322866 2.619137 2.942003 With this patchset (Energy in Joules): ----------------------------------------------- 0.226421 2.283658 2.510079 0.151361 2.236656 2.388017 0.197726 2.249849 2.447575 0.221915 2.229446 2.451361 0.347098 2.257707 2.604805 Average: 0.2289042 2.2514632 2.4803674 Above tests are repeated multiple times and events are tracked using trace-cmd and analysed using kernelshark. And it was easily noticeable that idle time for many cpus has increased considerably, which eventually saved some power. V4->V5: ------- - Created new wq flag: WQ_POWER_EFFICIENT, config option: CONFIG_WQ_POWER_EFFICIENT and kernel param workqueue.power_efficient. - Created few system wide workqueues aligned towards power saving. V3->V4: ------- - Dropped changes to kernel/sched directory and hence sched_select_non_idle_cpu(). - Dropped queue_work_on_any_cpu() - Created system_freezable_unbound_wq - Changed all patches accordingly. V2->V3: ------- - Dropped changes into core queue_work() API, rather create *_on_any_cpu() APIs - Dropped running timers migration patch as that was broken - Migrated few users of workqueues to use *_on_any_cpu() APIs. Viresh Kumar (5): workqueues: Introduce new flag WQ_POWER_EFFICIENT for power oriented workqueues workqueue: Add system wide power_efficient workqueues PHYLIB: queue work on system_power_efficient_wq block: queue work on power efficient wq fbcon: queue work on power efficient wq Documentation/kernel-parameters.txt | 17 +++++++++++++++++ block/blk-core.c | 3 ++- block/blk-ioc.c | 3 ++- block/genhd.c | 12 ++++++++---- drivers/net/phy/phy.c | 9 +++++---- drivers/video/console/fbcon.c | 2 +- include/linux/workqueue.h | 10 ++++++++++ kernel/power/Kconfig | 19 +++++++++++++++++++ kernel/workqueue.c | 24 +++++++++++++++++++++++- 9 files changed, 87 insertions(+), 12 deletions(-) -- 1.7.12.rc2.18.g61b472e -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
