Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759440AbZCZOu1 (ORCPT ); Thu, 26 Mar 2009 10:50:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759174AbZCZOtE (ORCPT ); Thu, 26 Mar 2009 10:49:04 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:48670 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759150AbZCZOtD (ORCPT ); Thu, 26 Mar 2009 10:49:03 -0400 Date: Thu, 26 Mar 2009 07:38:51 -0700 From: Andrew Morton To: Ingo Molnar Cc: Jan Kara , Linus Torvalds , Theodore Tso , Alan Cox , Arjan van de Ven , Peter Zijlstra , Nick Piggin , Jens Axboe , David Rees , Jesper Krogh , Linux Kernel Mailing List , Oleg Nesterov , Roland McGrath Subject: Re: ext3 IO latency measurements (was: Linux 2.6.29) Message-Id: <20090326073851.fcee79dd.akpm@linux-foundation.org> In-Reply-To: <20090326090630.GA9369@elte.hu> References: <20090324103111.GA26691@elte.hu> <20090324041249.1133efb6.akpm@linux-foundation.org> <20090325123744.GK23439@duck.suse.cz> <20090325150041.GM32307@mit.edu> <20090325185824.GO32307@mit.edu> <20090325215137.GQ32307@mit.edu> <20090325235041.GA11024@duck.suse.cz> <20090326090630.GA9369@elte.hu> X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.5; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2163 Lines: 47 On Thu, 26 Mar 2009 10:06:30 +0100 Ingo Molnar wrote: > And it's not just sys_fsync(). The script i wrote tests file read > latencies. I have created 1000 files with the same size (all copies > of kernel/sched.c ;-), and tested their cache-cold plain-cat > performance via: > > for ((i=0;i<1000;i++)); do > printf "file #%4d, plain reading it took: " $i > /usr/bin/time -f "%e seconds." cat $i >/dev/null > done > > I.e. plain, supposedly high-prio reads. The result is very common > hickups in read latencies: > > file # 579 (253560 bytes), reading it took: 0.08 seconds. > file # 580 (253560 bytes), reading it took: 0.05 seconds. > file # 581 (253560 bytes), reading it took: 0.01 seconds. > file # 582 (253560 bytes), reading it took: 0.01 seconds. > file # 583 (253560 bytes), reading it took: 4.61 seconds. > file # 584 (253560 bytes), reading it took: 1.29 seconds. > file # 585 (253560 bytes), reading it took: 3.01 seconds. > file # 586 (253560 bytes), reading it took: 7.74 seconds. > file # 587 (253560 bytes), reading it took: 3.22 seconds. > file # 588 (253560 bytes), reading it took: 0.05 seconds. > file # 589 (253560 bytes), reading it took: 0.36 seconds. > file # 590 (253560 bytes), reading it took: 7.39 seconds. > file # 591 (253560 bytes), reading it took: 7.58 seconds. > file # 592 (253560 bytes), reading it took: 7.90 seconds. > file # 593 (253560 bytes), reading it took: 8.78 seconds. > file # 594 (253560 bytes), reading it took: 8.01 seconds. > file # 595 (253560 bytes), reading it took: 7.47 seconds. > file # 596 (253560 bytes), reading it took: 11.52 seconds. > file # 597 (253560 bytes), reading it took: 10.33 seconds. > file # 598 (253560 bytes), reading it took: 8.56 seconds. > file # 599 (253560 bytes), reading it took: 7.58 seconds. (gets deja-vu feelings) http://lkml.org/lkml/2003/2/21/10 Maybe you should be running a 2.5.61 kernel. -- 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/