Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752603AbYJ0KnG (ORCPT ); Mon, 27 Oct 2008 06:43:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751559AbYJ0Kmw (ORCPT ); Mon, 27 Oct 2008 06:42:52 -0400 Received: from styx.suse.cz ([82.119.242.94]:50382 "EHLO mail.suse.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751406AbYJ0Kmv (ORCPT ); Mon, 27 Oct 2008 06:42:51 -0400 Date: Mon, 27 Oct 2008 11:42:50 +0100 (CET) From: Jiri Kosina To: Andrew Morton cc: Peter Zijlstra , Mike Galbraith , David Miller , rjw@sisk.pl, Ingo Molnar , s0mbre@tservice.net.ru, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [tbench regression fixes]: digging out smelly deadmen. In-Reply-To: Message-ID: References: <20081024.221653.23695396.davem@davemloft.net> <1224914333.3822.18.camel@marge.simson.net> <1224917623.4929.15.camel@marge.simson.net> <20081025.002420.82739316.davem@davemloft.net> <1225010790.8566.22.camel@marge.simson.net> <1225011648.27415.4.camel@twins> <20081026021153.47878580.akpm@linux-foundation.org> User-Agent: Alpine 1.10 (LNX 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1488 Lines: 43 On Sun, 26 Oct 2008, Jiri Kosina wrote: > > > > > 208.4 MB/sec -- vanilla 2.6.16.60 > > > > > 201.6 MB/sec -- vanilla 2.6.20.1 > > > > > 172.9 MB/sec -- vanilla 2.6.22.19 > > > > > 74.2 MB/sec -- vanilla 2.6.23 > > > > > 46.1 MB/sec -- vanilla 2.6.24.2 > > > > > 30.6 MB/sec -- vanilla 2.6.26.1 > > > > > I.e. huge drop for 2.6.23 (this was with default configs for each > > > > > respective kernel). > > Was this when we decreased the default value of > > /proc/sys/vm/dirty_ratio, perhaps? dbench is sensitive to that. > 2.6.28 gives 41.8 MB/s with /proc/sys/vm/dirty_ratio == 50. So small > improvement, but still far far away from the throughput of pre-2.6.23 > kernels. Ok, so another important datapoint: with c1e4fe711a4 (just before CFS has been merged for 2.6.23), the dbench throughput measures 187.7 MB/s in our testing conditions (default config). With c31f2e8a42c4 (just after CFS has been merged for 2.6.23), the throughput measured by dbench is 82.3 MB/s This is the huge drop we have been looking for. After this, the performance was still going down gradually, up to ~45 MS/ we are measuring for 2.6.27. But the biggest drop (more than 50%) points directly to CFS merge. -- Jiri Kosina SUSE Labs -- 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/