On Thu, 2014-04-24 at 18:52 +0200, Peter Zijlstra wrote: > On Thu, Apr 24, 2014 at 09:43:09AM -0700, Jason Low wrote: > > If the below patch is what you were referring to, I believe this > > can help too. This was also something that I was testing out before > > we went with those patches which compares avg_idle with idle balance > > cost. I recall seeing somewhere around a +7% performance improvement > > in at least least 1 of the AIM7 workloads. I can do some more testing > > with this. > > Yes, exactly that. > > I can't remember the details, but I suspect we feared the less agressive > idle balance due to that patch (it will only pull a single task, instead > of multiple) would cause more idle_balance invocations and thereby > decrease throughput. > > So I suppose something with _many_ bursty threads which leads to severe > inequalities would be the workload to trigger that. > > Not sure we've ever seen that.. maybe Mike remembers, he seems to have a > head for such details.
Okay, so running the AIM7 fserver workload, I didn't see any noticeable performance gains with having move_tasks() pull at most one task. The +7% performance improvement that I saw was without the idle balance cost patches. I think that with those idle balance cost patches, there aren't as much benefits with this patch, and allowing more than 1 task to be pulled in move_task(), like we have now, may be the best option. -- 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/
