From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.11] helo=sc8-sf-mx1.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Exim 4.30) id 1BgJdd-0008I0-IS for user-mode-linux-devel@lists.sourceforge.net; Fri, 02 Jul 2004 01:43:17 -0700 Received: from letters.cs.ucsb.edu ([128.111.41.13]) by sc8-sf-mx1.sourceforge.net with esmtp (Exim 4.34) id 1BgJdd-0004nj-9K for user-mode-linux-devel@lists.sourceforge.net; Fri, 02 Jul 2004 01:43:17 -0700 Received: from cs.ucsb.edu (SY197111.resnet.ucsb.edu [128.111.197.111]) by letters.cs.ucsb.edu (8.11.7+Sun/8.11.7) with ESMTP id i628hGT02742 for ; Fri, 2 Jul 2004 01:43:16 -0700 (PDT) Message-ID: <40E51FF0.3020801@cs.ucsb.edu> From: "Lamia M.Youseff" MIME-Version: 1.0 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit Subject: [uml-devel] does O_DIRECT hinder greatly file reading performance but not writing?? Sender: user-mode-linux-devel-admin@lists.sourceforge.net Errors-To: user-mode-linux-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: The user-mode Linux development list List-Post: List-Help: List-Subscribe: , List-Archive: Date: Fri, 02 Jul 2004 01:42:24 -0700 To: user-mode-linux-devel@lists.sourceforge.net Hi All,

I am kind of new to UML and I am experiencing a very strange performance hinder with it.
I am running two benchmarks; one that writes a 50Mbyte file and the other one reads a 50Mbyte file.
I tried the benchmarks with and without setting the O_DIRECT flag, in which cases the whole task is done in a matter of seconds(10-30 seconds) except when reading the file with O_DIRECT flag on. In this case, it takes 18-20 min!!!

I am running UML 2.4.19 on top of kernel 2.4.25.  I have time output like that (average of 20 runs)

Operation	User Time (sec)	Sys Time(sec)	Wall Clock Time(sec)
Write Without O_DIRECT	5.612000	0.117500	27.164500
Write With O_DIRECT	10.007000	0.017000	22.199500
Read without O_DIRECT	3.035000	0.091000	7.760000
Read With O_DIRECT	21.492000	29.680000	1133.054000

I would appreciate it very much if somebody would explain to me how to solve that strange performance problem, or even explain why does it happen for reading with O_DIRECT but not without !!??

Thanks allot,
Lamia Youseff
--

I am kind of new to UML and I am experiencing a very strange performance hinder with it.
I am running two benchmarks; one that writes a 50Mbyte file and the other one reads a 50Mbyte file.
I tried the benchmarks with and without setting the O_DIRECT flag, in which cases the whole task is done in a matter of seconds(10-30 seconds) except when reading the file with O_DIRECT flag on. In this case, it takes 18-20 min!!!

I am running UML 2.4.19 on top of kernel 2.4.25.  I have time output like that (average of 20 runs)

Operation	User Time (sec)	Sys Time(sec)	Wall Clock Time(sec)
Write Without O_DIRECT	5.612000	0.117500	27.164500
Write With O_DIRECT	10.007000	0.017000	22.199500
Read without O_DIRECT	3.035000	0.091000	7.760000
Read With O_DIRECT	21.492000	29.680000	1133.054000

I would appreciate it very much if somebody would explain to me how to solve that strange performance problem, or even explain why does it happen for reading with O_DIRECT but not without !!??

Thanks allot,
Lamia Youseff
--

------------------------------------------------------- This SF.Net email sponsored by Black Hat Briefings & Training. Attend Black Hat Briefings & Training, Las Vegas July 24-29 - digital self defense, top technical experts, no vendor pitches, unmatched networking opportunities. Visit www.blackhat.com _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx2-b.sourceforge.net ([10.3.1.12] helo=sc8-sf-mx2.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Exim 4.30) id 1BgRmj-000708-UJ for user-mode-linux-devel@lists.sourceforge.net; Fri, 02 Jul 2004 10:25:13 -0700 Received: from mail1.engr.ucsb.edu ([128.111.53.4] helo=smtp.engr.ucsb.edu) by sc8-sf-mx2.sourceforge.net with esmtp (TLSv1:DES-CBC3-SHA:168) (Exim 4.34) id 1BgRmj-0008Mf-LN for user-mode-linux-devel@lists.sourceforge.net; Fri, 02 Jul 2004 10:25:13 -0700 Received: from www1.engr.ucsb.edu ([128.111.27.8]:3451 helo=cs.ucsb.edu) by smtp.engr.ucsb.edu with smtp (Exim 4.24) id 1BgRmc-00079E-Gg for user-mode-linux-devel@lists.sourceforge.net; Fri, 02 Jul 2004 10:25:06 -0700 From: In-Reply-To: <40E520AE.8040302@cs.ucsb.edu> Message-Id: Subject: [uml-devel] Re: does O_DIRECT hinder greatly file reading performance but not writing?? Sender: user-mode-linux-devel-admin@lists.sourceforge.net Errors-To: user-mode-linux-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: The user-mode Linux development list List-Post: List-Help: List-Subscribe: , List-Archive: Date: Fri, 2 Jul 2004 17:25:09 -0000 To: user-mode-linux-devel@lists.sourceforge.net Sorry for the repeated posts, but i figured out that my email body was not posted. My appologies for the spam. --------------------------------- Hi All, I am kind of new to UML and I am experiencing a very strange performance hinder with it. I am running two benchmarks; one that writes a 50Mbyte file and the other one reads a 50Mbyte file. I tried the benchmarks with and without setting the O_DIRECT flag, in which cases the whole task is done in a matter of seconds(10-30 seconds) except when reading the file with O_DIRECT flag on. In this case, it takes 18-20 min!!! I am running UML 2.4.19 on top of kernel 2.4.25. I have time output like that (average of 20 runs) Operation UserTime(sec) SysTime(sec) WallClockTime(sec) Write Without O_DIRECT 5.612000 0.117500 27.164500 Write With O_DIRECT 10.007000 0.017000 22.199500 Read without O_DIRECT 3.035000 0.091000 7.760000 Read With O_DIRECT 21.492000 29.680000 1133.054000 I would appreciate it very much if somebody would explain to me how to solve that strange performance problem, or even explain why does it happen for reading with O_DIRECT but not without !!?? Thanks allot, Lamia Youseff -- ------------------------------------------------------- This SF.Net email sponsored by Black Hat Briefings & Training. Attend Black Hat Briefings & Training, Las Vegas July 24-29 - digital self defense, top technical experts, no vendor pitches, unmatched networking opportunities. Visit www.blackhat.com _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel