Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754950Ab1C3CQ1 (ORCPT ); Tue, 29 Mar 2011 22:16:27 -0400 Received: from mail-fx0-f46.google.com ([209.85.161.46]:61786 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753978Ab1C3CQZ (ORCPT ); Tue, 29 Mar 2011 22:16:25 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=LN2K8KA2y84yrVkqRXVK8wTzmLEHIxW73BopbFVJ0gppL/RhsOdXDMSit2p/jrFiE8 vh8es/wElPukCHNxf/3q2V5fNCP0aUnh/ofst3vQCIRv32wVwhAr1ZwZMng1rK6KbIyU YXdg6bpX6wrXauhIiA+znhjJ/+5wdHH/Y71hg= MIME-Version: 1.0 In-Reply-To: References: Date: Wed, 30 Mar 2011 02:16:24 +0000 Message-ID: Subject: Re: ioprio_set: IDLE_CLASS doesn't work as its name suggests From: "fykcee1@gmail.com" To: linux-kernel@vger.kernel.org Cc: Heihaier Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2427 Lines: 68 I/O activity of IOPRIO_CLASS_IDLE processes can reduce other's I/O performance by nearly half, according to http://dev.lemote.com/files/upload/people/~chenj/effect_of_IO_IDLE.png. It seems "IDLE" in "IOPRIO_CLASS_IDLE" is not analogized to "IDLE" in "SCHED_IDLE", is it the normal behavior? 2011/3/26 fykcee1@gmail.com > > Hi all, > > I've tried to make a fast boot according to "Booting Linux in five > seconds"[1]. One method of boot fast is using readahead -- a process > "replay" read actions in IDLE IO class via readahead syscall. Sadly > observed negative results -- according to bootchat diagram, readahead > process actually uses more IO bandwidth that slows down all IO > operations of other ones. > > Then I did some tests -- two I/O hog processes, the IDLE IO class one > largely degrades I/O performance of the other one. > > The tests were performed on a machine with dual-core cpu (intel > E5400@2.7GHz), G33 and ICH7, 2G mem, running Ubuntu 10.04. The kernel > version was 2.6.35-25-generic with CFQ as default I/O scheduler. > We ran test programs which time "find $2 -type f -exec cat {} \;" on > ~1.9G directory with Normal and IDLE IO class. Before each test, we > reboot the system. Here are the results: > > 1. Only ran one instance of the test program in Normal IO class: > Job finished in 4m2.365s > > 2. Ran two instances of the test program, one Normal IO class, the > other Idle IO class: > [Normal]: 7m0.999s > [Idle]: 7m43.180s > > 3. Ran two instances of the test program, both Normal IO class: > [Normal1]: 8m39.366s > [Normal2]: 8m39.377s > > BTW, for those interested in the detail, try the attachment: > 1. mkdir ioprio_test > 2. cp ioprio_test.c run_test.sh ioprio_test > 3. tar xf -C ioprio_test/tdir1 > 4. tar xf -C ioprio_test/tdir2 > 5. reboot; cd ioprio_test && ./run_test.sh 1 => result stored in F.txt > 6. reboot; cd ioprio_test && ./run_test.sh 2 => result stored in > F[B0].txt B0[F].txt > 7. reboot; cd ioprio_test && ./run_test.sh 3 => result stored in > F[B1].txt B1[F].txt > > > > Regards, > cee1 > ------- > [1] http://lwn.net/Articles/299483/ -- Regards, - cee1 -- 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/