From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from host-181-75-169-83.static.internet-fr.net ([83.169.75.181]:54706 "EHLO seanodes.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752861AbYKSNPN (ORCPT ); Wed, 19 Nov 2008 08:15:13 -0500 Message-ID: <4924115E.6040701@seanodes.com> Date: Wed, 19 Nov 2008 14:15:10 +0100 From: Erwan Velu MIME-Version: 1.0 Subject: Help required to understand fio output Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: fio-owner@vger.kernel.org List-Id: fio@vger.kernel.org To: fio@vger.kernel.org Here come a typical output I have using fio. I added some line numbers as an helper. 01: /dev/mydisk: (groupid=1, jobs=1): err= 0: pid=7433 02: write: io=79,112MiB, bw=72,774KiB/s, iops=740, runt=1139888msec 03: slat (usec): min=9, max=572, avg=21.22, stdev= 7.03 04: clat (msec): min=2, max=668, avg=86.43, stdev=24.47 05: bw (KiB/s) : min= 0, max=80749, per=100.06%, avg=72815.92, stdev=2318.78 06: cpu : usr=0.93%, sys=1.35%, ctx=722885, majf=0, minf=10031 07: IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%, >=64=100.0% 08: submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% 09: complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.1%, >=64=0.0% 10: issued r/w: total=0/843855, short=0/0 11: 12: lat (msec): 4=0.01%, 10=0.03%, 20=0.38%, 50=6.53%, 100=64.24% 13: lat (msec): 250=28.79%, 500=0.01%, 750=0.01% I have some questions about the output. About Latencies: Line 4, clat is reported to be at 86ms as average but line 12 is is written that 100=64 250=29 What's the meaning of "100=" ? Does it means "there were 64% of IOs completed between 100 & 249 ms ?" If yes, that's pretty surprising that while having 95% of my IOs that are completed in more than 100ms, the average is reported as 86. If "100=" means "IO between 50 and 99ms", thus output become pretty confusing. About IO depths: In my config file I had set a depth to 64. Line 07 reports that 100% of my IOs where >=64... cool but is it also said that 0.6% were spent on <=64K Sounds to be a rounding effect but does this really means that some IOs where sent with a short depth ? And then, how should I understan lines 8 & 9 that reports that 100% of IOs were completed with a depth=4... What happened ? Hope this questions aren't too stupid ;o) Thanks, -- Erwan Velu Pre-Sales Engineer Seanodes http://www.seanodes.com +33 (0)1 41 22 13 83