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Message-ID: <45E21FEC.9060605@redhat.com> Date: Sun, 25 Feb 2007 18:46:52 -0500 From: Rik van Riel <riel@...hat.com> To: Lorenzo Allegrucci <l_allegrucci@...oo.it> CC: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>, Suparna Bhattacharya <suparna@...ibm.com>, Jens Axboe <jens.axboe@...cle.com> Subject: Re: SMP performance degradation with sysbench Lorenzo Allegrucci wrote: > Hi lkml, > > according to the test below (sysbench) Linux seems to have scalability > problems beyond 8 client threads: > http://jeffr-tech.livejournal.com/6268.html#cutid1 > http://jeffr-tech.livejournal.com/5705.html > Hardware is an 8-core amd64 system and jeffr seems willing to try more > Linux versions on that machine. > Anyway, is there anyone who can reproduce this? I have reproduced it on a quad core test system. With 4 threads (on 4 cores) I get a high throughput, with approximately 58% user time and 42% system time. With 8 threads (on 4 cores) I get way lower throughput, with 37% user time, 29% system time 35% idle time! The maximum time taken per query also increases from 0.0096s to 0.5273s. Ouch! I don't know if this is MySQL, glibc or Linux kernel, but something strange is going on... -- Politics is the struggle between those who want to make their country the best in the world, and those who believe it already is. Each group calls the other unpatriotic. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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