Messages in this thread | | | From | "Hillf Danton" <> | Subject | RE: [PATCH v8 03/10] sched: move cfs task on a CPU with higher capacity | Date | Tue, 04 Nov 2014 20:54:29 +0800 |
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> > On 4 November 2014 13:07, Hillf Danton <hillf.zj@alibaba-inc.com> wrote: > >> >> + /* > >> >> + * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task. > >> > > >> > > >> > Why specify one task instead of not less than one? > >> > >> if cfs.h_nr_running = 0 (which should not occurs at that point), we > >> don't need to do more test to check if it's worth moving the task > >> because there is no task to move. > >> > > I wonder if you can please shed light on the case that > > the dst_cpu is newly idle. > > The main problem if we do the test only for newly idle case, is that > we are not sure to move the task because we must rely on the > wakeup/sleep sequence of other tasks on an idle CPU in order to trig > the migration (periodic background task as an example). So we might > never move the task whereas idle CPUs are available > So no task is migrated in the newly idle case, if I understand the above correctly.
Hillf
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