On Wednesday, December 09, 2015 07:34:42 AM Viresh Kumar wrote: > cpufreq governors evaluate load at sampling rate and based on that they > update frequency for a group of CPUs belonging to the same cpufreq > policy. > > This is required to be done in a single thread for all policy->cpus, but > because we don't want to wakeup idle CPUs to do just that, we use > deferrable work for this. If we would have used a single delayed > deferrable work for the entire policy, there were chances that the CPU > required to run the handler can be in idle and we might end up not > changing the frequency for the entire group with load variations. > > And so we were forced to keep per-cpu works, and only the one that > expires first need to do the real work and others are rescheduled for > next sampling time. > > We have been using the more complex solution until now, where we used a > delayed deferrable work for this, which is a combination of a timer and > a work. > > This could be made lightweight by keeping per-cpu deferred timers with a > single work item, which is scheduled by the first timer that expires. > > This patch does just that and here are important changes: > - The timer handler will run in irq context and so we need to use a > spin_lock instead of the timer_mutex. And so a separate timer_lock is > created. This also makes the use of the mutex and lock quite clear, as > we know what exactly they are protecting. > - A new field 'skip_work' is added to track when the timer handlers can > queue a work. More comments present in code. > > Suggested-by: Rafael J. Wysocki <[email protected]> > Signed-off-by: Viresh Kumar <[email protected]> > Reviewed-by: Ashwin Chaugule <[email protected]>
OK, replaced the one in my tree with this one, thanks! BTW, can you please add an extra From: line to the bodies of your patch messages? For some unknown reason Patchwork or your mailer or the combination of the two mangles your name for me and I have to fix it up manually in every patch from you which is a !@#$%^&*() pain. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
