On 27 September 2012 14:34, Viresh Kumar viresh.kumar@linaro.org wrote:
This is V2 of my sched_select_cpu() work.
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.
- Second patch removes idle_cpu() calls from timer & hrtimer.
- Third patch is about adapting this change in workqueue framework.
Earlier discussions over v1 can be found here: http://www.mail-archive.com/linaro-dev@lists.linaro.org/msg13342.html
Earlier discussions over this concept were done at last LPC: http://summit.linuxplumbersconf.org/lpc-2012/meeting/90/lpc2012-sched-timer-...
Module created for testing this behavior is present here: http://git.linaro.org/gitweb?p=people/vireshk/module.git%3Ba=summary
Following are the steps followed in test module:
- Run single work on each cpu
- This work will start a timer after x (tested with 10) jiffies of delay
- Timer routine queues a work... (This may be called from idle or non-idle cpu) and starts the same timer again STEP 3 is done for n number of times (i.e. queuing n works, one after other)
- All works will call a single routine, which will count following per cpu:
- Total works processed by a CPU
- Total works processed by a CPU, which are queued from it
- Total works processed by a CPU, which aren't queued from it
Setup:
- ARM Vexpress TC2 - big.LITTLE CPU
- Core 0-1: A15, 2-4: A7
- rootfs: linaro-ubuntu-nano
Results:
Without Workqueue Modification, i.e. PATCH 3/3: [ 2493.022335] Workqueue Analyser: works processsed by CPU0, Total: 1000, Own: 0, migrated: 0 [ 2493.047789] Workqueue Analyser: works processsed by CPU1, Total: 1000, Own: 0, migrated: 0 [ 2493.072918] Workqueue Analyser: works processsed by CPU2, Total: 1000, Own: 0, migrated: 0 [ 2493.098576] Workqueue Analyser: works processsed by CPU3, Total: 1000, Own: 0, migrated: 0 [ 2493.123702] Workqueue Analyser: works processsed by CPU4, Total: 1000, Own: 0, migrated: 0
With Workqueue Modification, i.e. PATCH 3/3: [ 2493.022335] Workqueue Analyser: works processsed by CPU0, Total: 1002, Own: 999, migrated: 3 [ 2493.047789] Workqueue Analyser: works processsed by CPU1, Total: 998, Own: 997, migrated: 1 [ 2493.072918] Workqueue Analyser: works processsed by CPU2, Total: 1013, Own: 996, migrated: 17 [ 2493.098576] Workqueue Analyser: works processsed by CPU3, Total: 998, Own: 993, migrated: 5 [ 2493.123702] Workqueue Analyser: works processsed by CPU4, Total: 989, Own: 987, migrated: 2
V1->V2
- New SD_* macros removed now and earlier ones used
- sched_select_cpu() rewritten and it includes the check on current cpu's idleness.
- cpu_idle() calls from timer and hrtimer removed now.
- Patch 2/3 from V1, removed as it doesn't apply to latest workqueue branch from tejun.
- CONFIG_MIGRATE_WQ removed and so is wq_select_cpu()
- sched_select_cpu() called only from __queue_work()
- got tejun/for-3.7 branch in my tree, before making workqueue changes.
Viresh Kumar (3): sched: Create sched_select_cpu() to give preferred CPU for power saving timer: hrtimer: Don't check idle_cpu() before calling get_nohz_timer_target() workqueue: Schedule work on non-idle cpu instead of current one
Hi Guys,
I totally understand since last few weeks you guys were very busy as the merge window was around. So, didn't tried to disturb you then :)
Can you please share your viewpoint on this patchset now? And also the running timer migration patch (which was sent separately)?
Thanks in Advance.
-- viresh