In order to save power, it would be useful to schedule work onto non-IDLE cpus instead of waking up an IDLE one.
To achieve this, we need scheduler to guide kernel frameworks (like: timers & workqueues) on which is the most preferred CPU that must be used for these tasks. This patchset is about implementing this concept. The first patch adds sched_select_cpu() routine which returns the preferred cpu which is non-idle. It accepts max level of sched domain, upto which we can choose a CPU from. It can accept following options: SD_SIBLING, SD_MC, SD_BOOK, SD_CPU or SD_NUMA. Second and Third patch are about adapting this change in workqueue framework. Earlier discussions over this concept were done at last LPC: http://summit.linuxplumbersconf.org/lpc-2012/meeting/90/lpc2012-sched-timer-workqueue/ Figures: -------- Test case 1: - Performed on TC2 with ubuntu-devel - Boot TC2 and run $ trace-cmd record -e workqueue_execute_start This will trace only the points, where the work actually runs. Do, this for 150 seconds. Results: --------- Domain 0: CPU 0-1 Domain 1: CPU 2-4 Base Kernel: Without my modifications: ------------------------------------- CPU No. of works run by CPU ----- ----------------------- CPU0: 7 CPU1: 445 CPU2: 444 CPU3: 315 CPU4: 226 With my modifications: ---------------------- CPU No. of works run by CPU ---- ----------------------- CPU0: 31 CPU2: 797 CPU3: 274 CPU4: 86 Test case 2: ----------- I have created a small module, which does following: - Create one work for each CPU (using queue_work_on(), so must schedule on that cpu) - Above work, will queue "n" works for each cpu with queue_work(). These works are tracked within the module and results are printed at the end. This gave similar results, with n ranging from 10 to 1000. Viresh Kumar (3): sched: Create sched_select_cpu() to give preferred CPU for power saving workqueue: create __flush_delayed_work to avoid duplicating code workqueue: Schedule work on non-idle cpu instead of current one arch/arm/Kconfig | 11 +++++++ include/linux/sched.h | 11 +++++++ kernel/sched/core.c | 88 +++++++++++++++++++++++++++++++++++++++------------ kernel/workqueue.c | 36 ++++++++++++++------- 4 files changed, 115 insertions(+), 31 deletions(-) -- 1.7.12.rc2.18.g61b472e -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
