Messages in this thread | | | Date | Sat, 20 Nov 2004 14:58:36 +1100 | From | Nick Piggin <> | Subject | Re: page fault scalability patch V11 [0/7]: overview |
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William Lee Irwin III wrote: > William Lee Irwin III wrote: > >>>Irrelevant. Unshare cachelines with hot mm-global ones, and the >>>"problem" goes away. > > > On Sat, Nov 20, 2004 at 02:14:33PM +1100, Nick Piggin wrote: > >>That's the idea. > > > > William Lee Irwin III wrote: > >>>This stuff is going on and on about some purist "no atomic operations >>>anywhere" weirdness even though killing the last atomic operation >>>creates problems and doesn't improve performance. > > > On Sat, Nov 20, 2004 at 02:14:33PM +1100, Nick Piggin wrote: > >>Huh? How is not wanting to impact single threaded performance being >>"purist weirdness"? Practical, I'd call it. > > > Empirically demonstrate the impact on single-threaded performance. >
I can tell you its worse. I don't have to demonstrate anything, more atomic RMW ops in the page fault path is going to have an impact.
I'm not saying we must not compromise *anywhere*, but it would just be nice to try to avoid making the path heavier, that's all. I'm not being purist when I say I'd first rather explore all other options before adding atomics.
But nevermind arguing, it appears Linus' suggested method will be fine and *does* mean we don't have to compromise.
> > On Sat, Nov 20, 2004 at 01:40:40PM +1100, Nick Piggin wrote: > >>>Why the Hell would you bother giving each cpu a separate cacheline? >>>The odds of bouncing significantly merely amongst the counters are not >>>particularly high. > > > On Sat, Nov 20, 2004 at 02:14:33PM +1100, Nick Piggin wrote: > >>Hmm yeah I guess wouldn't put them all on different cachelines. >>As you can see though, Christoph ran into a wall at 8 CPUs, so >>having them densly packed still might not be enough. > > > Please be more specific about the result, and cite the Message-Id. >
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