Messages in this thread | | | From | Wanpeng Li <> | Date | Tue, 10 Dec 2019 19:15:34 +0800 | Subject | Re: [PATCH V3 0/2] sched/fair: Fallback to sched-idle CPU in absence of idle CPUs |
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On Tue, 10 Dec 2019 at 14:33, Viresh Kumar <viresh.kumar@linaro.org> wrote: > > On 09-12-19, 11:50, Wanpeng Li wrote: > > On Wed, 26 Jun 2019 at 13:07, Viresh Kumar <viresh.kumar@linaro.org> wrote: > > > > > > Hi, > > > > > > We try to find an idle CPU to run the next task, but in case we don't > > > find an idle CPU it is better to pick a CPU which will run the task the > > > soonest, for performance reason. > > > > > > A CPU which isn't idle but has only SCHED_IDLE activity queued on it > > > should be a good target based on this criteria as any normal fair task > > > will most likely preempt the currently running SCHED_IDLE task > > > immediately. In fact, choosing a SCHED_IDLE CPU over a fully idle one > > > shall give better results as it should be able to run the task sooner > > > than an idle CPU (which requires to be woken up from an idle state). > > > > > > This patchset updates both fast and slow paths with this optimization. > > > > > > Testing is done with the help of rt-app currently and here are the > > > details: > > > > > > - Tested on Octacore Hikey platform (all CPUs change frequency > > > together). > > > > > > - rt-app json [1] creates few tasks and we monitor the scheduling > > > latency for them by looking at "wu_lat" field (usec). > > > > > > - The histograms are created using > > > https://github.com/adkein/textogram: textogram -a 0 -z 1000 -n 10 > > > > > > - the stats are accumulated using: https://github.com/nferraz/st > > > > Hi Viresh, > > > > Thanks for the great work! Could you give the whole commad-line for us testing? > > The rt-app json [1] can be run using: > > $ rt-app sched-idle.json > > This will create couple of files named rt-app-cfs_thread-*.log and > rt-app-idle_thread-*.log. I looked mostly at the cfs files here as that's what > we were looking for. We will be interested only in the last column of these > files, which says "wu_lat". Remove everything apart from that column (and remove > the first row as well, which has field names) from all cfs files (or write a > sed/awk command to do it for you. > > After that I you can generate the numbers (mean/max/min/etc) using: > > $ st rt-app-cfs_thread-*.log
Thanks for pointing out this.
Wanpeng
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