Christoph Hellwig wrote:
On Thu, May 03, 2007 at 11:32:23AM +1000, Nick Piggin wrote:The attached patch gets performance up a bit by avoiding some barriers and some cachelines: G5 pagefault fork exec 2.6.21 1.49-1.51 164.6-170.8 741.8-760.3 +patch 1.71-1.73 175.2-180.8 780.5-794.2 +patch2 1.61-1.63 169.8-175.0 748.6-757.0 So that brings the fork/exec hits down to much less than 5%, and would likely speed up other things that lock the page, like write or page reclaim.Is that every fork/exec or just under certain cicumstances? A 5% regression on every fork/exec is not acceptable.
Well after patch2, G5 fork is 3% and exec is 1%, I'd say the P4 numbers will be improved as well with that patch. Then if we have specific lock/unlock bitops, I hope it should reduce that further. The overhead that is there should just be coming from the extra overhead in the file backed fault handler. For noop fork/execs, I think that tends to be more pronounced, it is hard to see any difference on any non-micro benchmark. The other thing is that I think there could be some cache effects happening -- for example the exec numbers on the 2nd line are disproportionately large. It definitely isn't a good thing to drop performance anywhere though, so I'll keep looking for improvements. -- SUSE Labs, Novell Inc. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
