On Mon, 2012-09-17 at 12:07 +0200, Ingo Molnar wrote: > * Mike Galbraith <efa...@gmx.de> wrote: >
> > 4 socket 40 core + SMT Westmere box, single 30 sec tbench runs, higher > > is better: > > > > clients 1 2 4 8 16 32 64 > > 128 > > > > .......................................................................... > > pre 30 41 118 645 3769 6214 12233 > > 14312 > > post 299 603 1211 2418 4697 6847 11606 > > 14557 > > That's a very tempting speedup for a simpler and more > fundamental workload than postgresql's somewhat weird > user-space spinlocks that burn CPU time in user-space > instead of blocking/waiting on a futex. > > IIRC mysql does this properly and outperforms postgresql > on this benchmark, in an apples-to-apples configuration? It's been a while since I fiddled with oltp (lost my fast mysql db, every attempt to re-create produced a complete slug), but postgress was always the throughput winner at that here. > > 10x at 1 pair shouldn't be traversal, the whole box is > > otherwise idle. We'll do a lot more (ever more futile) > > traversal as load increases, but at the same time, our futile > > attempts fail more frequently, so we shoot ourselves in the > > foot less frequently. > > > > The down side is (appears to be) that I also shut down some > > ~odd case preemption salvation, salvation that only large > > packages will receive. > > > > The problem as I see it is that we're making light tasks _too_ > > mobile, turning an optimization into a pessimization for light > > tasks. For longer running tasks this mobility within a large > > package isn't such a big deal, but for fast movers, it hurts a > > lot. > > There's not enough time to resolve this for v3.6, so I agree > with the revert - would you be willing to post a v2 of your > original patch? I really think we want your tbench speedups, > quite a few real-world messaging applications use the tbench > patterns of scheduling. I don't know what a v2 would look like, but I can keep thinking about this irritating little <naughty words elided>. Peter's a lot hairier chested, not to mention having a sense of _taste_ :) so it might be better to just consider my patch a diagnostic, and let him fix it up in a (likely lots) less tummy distressing manner. -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/
