On Mon, Nov 26, 2012 at 11:40:27AM -0500, Steven Rostedt wrote: > On Mon, 2012-11-26 at 20:30 +0530, Viresh Kumar wrote: > > On 6 November 2012 16:08, Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote: > > > This is V2 Resend of my sched_select_cpu() work. Resend because didn't got much > > > attention on V2. Including more guys now in cc :) > > > > > > 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. > > > - Fourth patch add migration capability in running timer > > > > > > Earlier discussions over v1 can be found here: > > > http://www.mail-archive.com/linaro-dev@xxxxxxxxxxxxxxxx/msg13342.html > > > > > > Earlier discussions over this concept were done at last LPC: > > > http://summit.linuxplumbersconf.org/lpc-2012/meeting/90/lpc2012-sched-timer-workqueue/ > > > > > > Module created for testing this behavior is present here: > > > http://git.linaro.org/gitweb?p=people/vireshk/module.git;a=summary > > > > Ping!! > > This is a really bad time of year to post new patches :-/ > A lot of people are trying to get their own work done by year end and > then there's holidays and such that are also distractions. Not to > mention that a new merge window will be opening soon. > > That said... > > As workqueues are set off by the CPU that queued it, what real benefit > does this give? A CPU was active when it queued the work and the work > should be done before it gets back to sleep. > > OK, an interrupt happens on an idle CPU and queues some work. That work > should execute before the CPU gets back to sleep, right? I fail to see > the benefit of trying to move that work elsewhere. The CPU had to wake > up to execute the interrupt. It's no longer in a deep sleep (or any > sleep for that matter). > > To me it seems best to avoid waking up an idle CPU in the first place. > > I'm still working off a turkey overdose, so maybe I'm missing something > obvious. If I understand correctly (though also suffering turkey OD), the idea is to offload work to more energy-efficient CPUs. Thanx, Paul -- 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
