On Fri, 2014-05-02 at 06:56 -0400, Rik van Riel wrote: > On 05/02/2014 03:37 AM, Mike Galbraith wrote: > > On Fri, 2014-05-02 at 02:30 -0400, Rik van Riel wrote: > >> On 05/02/2014 02:13 AM, Mike Galbraith wrote: > >>> On Fri, 2014-05-02 at 00:42 -0400, Rik van Riel wrote: > >>> > >>>> Whether or not this is the right thing to do remains to be seen, > >>>> but it does allow us to verify whether or not the wake_affine > >>>> strategy of always doing affine wakeups and only disabling them > >>>> in a specific circumstance is sound, or needs rethinking... > >>> > >>> Yes, it needs rethinking. > >>> > >>> I know why you want to try this, yes, select_idle_sibling() is very much > >>> a two faced little bitch. > >> > >> My biggest problem with select_idle_sibling and wake_affine in > >> general is that it will override NUMA placement, even when > >> processes only wake each other up infrequently... > > > > Hm, seems the thing to do would be to tell select_task_rq_fair() to keep > > it's mitts off of tasks that the numasched stuff has placed rather than > > decapitating select_idle_sibling() or some other drastic measure. > > Thing is, if tasks are waking each other up frequently enough, we > probably DO want to place them near each other with select_idle_sibling.
Right. I'm thinking you could perhaps create a sched feature like NUMA_ME_HARDER or such so you can tell it to go away if you find that your load performs best when movement is left entirely up to the NUMA placement code. > We just cannot afford to have it as the default behaviour for casual > wakeup activity, because it will mess up other things. I think it is generally good, but yes, it has its bad it's bad side, why we have tweakables. -Mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/