On 02/21/2013 05:43 PM, Mike Galbraith wrote: > On Thu, 2013-02-21 at 17:08 +0800, Michael Wang wrote: > >> But is this patch set really cause regression on your Q6600? It may >> sacrificed some thing, but I still think it will benefit far more, >> especially on huge systems. > > We spread on FORK/EXEC, and will no longer will pull communicating tasks > back to a shared cache with the new logic preferring to leave wakee > remote, so while no, I haven't tested (will try to find round tuit) it > seems it _must_ hurt. Dragging data from one llc to the other on Q6600 > hurts a LOT. Every time a client and server are cross llc, it's a huge > hit. The previous logic pulled communicating tasks together right when > it matters the most, intermittent load... or interactive use.
I agree that this is a problem need to be solved, but don't agree that wake_affine() is the solution. According to my understanding, in the old world, wake_affine() will only be used if curr_cpu and prev_cpu share cache, which means they are in one package, whatever search in llc sd of curr_cpu or prev_cpu, we won't have the chance to spread the task out of that package. I'm going to recover the logical that only do select_idle_sibling() when prev_cpu and curr_cpu are affine, so now the new logical will only prefer leaving task in old package if both prev_cpu and curr_cpu are in that package, I think this could solve the problem, isn't it? Regards, Michael Wang > > -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/ > -- 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/
