Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030223AbXBZNli (ORCPT ); Mon, 26 Feb 2007 08:41:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030230AbXBZNli (ORCPT ); Mon, 26 Feb 2007 08:41:38 -0500 Received: from smtp105.plus.mail.mud.yahoo.com ([68.142.206.238]:30513 "HELO smtp105.plus.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1030223AbXBZNlh (ORCPT ); Mon, 26 Feb 2007 08:41:37 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:X-YMail-OSG:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=gcjoC+AzaKVcVPT6m6xN3E5bya4hgLEOkQJKZyl8M+dUfmICclazmqTJv6H8V3R3m8x9TUOcoTb7AX0MC339CXdeR5ypD6TGAWgQtgS4UFjMys/8wrsoW0GB98JZLRgxhTc1xTkq9fvT6t9+3Q/ddsavs05KQg+58xOkVjsuQV8= ; X-YMail-OSG: xbnaenYVM1lTHH8TjWtbpLazPBHAQ7o1.j7r4_XtpkmdyL43iFGCg6qZcbgb8iZauL2taR07g57epTcpSfk8S7Pte6Aq7PePG6hmCxyvDpAWQH4pp4FmTQ-- Message-ID: <45E2E38A.2010309@yahoo.com.au> Date: Tue, 27 Feb 2007 00:41:30 +1100 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20051007 Debian/1.7.12-1 X-Accept-Language: en MIME-Version: 1.0 To: Nick Piggin CC: Rik van Riel , Lorenzo Allegrucci , linux-kernel@vger.kernel.org, Ingo Molnar , Suparna Bhattacharya , Jens Axboe Subject: Re: SMP performance degradation with sysbench References: <1172425476.5489.11.camel@odyssey.lan> <45E21FEC.9060605@redhat.com> <45E2E244.8040009@yahoo.com.au> In-Reply-To: <45E2E244.8040009@yahoo.com.au> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1612 Lines: 49 Nick Piggin wrote: > Rik van Riel wrote: > >> 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... > > > Like you, I'm also seeing idle time start going up as threads increase. > > I initially thought this was a problem with the multiprocessor scheduler, > because the pattern is exactly like some artificat in the load balancing. "artificat" Wow. I must need some sleep :) Please excuse any other typos! -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/