Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937891AbZLHUnF (ORCPT ); Tue, 8 Dec 2009 15:43:05 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S936711AbZLHUnA (ORCPT ); Tue, 8 Dec 2009 15:43:00 -0500 Received: from mail-yx0-f187.google.com ([209.85.210.187]:34731 "EHLO mail-yx0-f187.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936476AbZLHUm7 (ORCPT ); Tue, 8 Dec 2009 15:42:59 -0500 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:content-transfer-encoding; b=W4l0t9RjI3ZW0luRg8SpVfjReQwWSwknPZ4D4QNuwPcBeHtDXkpYnFGmcKt8PX2D12 G6coTMSyNiY4FxINRYOE912VcPxRGsrR3mAjyNzQufbD+TbXwEhPFoxrYV84cA/salp2 17Y0aWYAmDm6nuvtBY8LlocUY//SB6Pzyl1mE= MIME-Version: 1.0 In-Reply-To: References: <4b1a3d84.0d0db80a.39d0.ffff814a@mx.google.com> <4e5e476b0912050313k280caa8bjf7c2cf1c5d19c88c@mail.gmail.com> <4e5e476b0912060245x4d64300hb9689243bd712f2c@mail.gmail.com> Date: Tue, 8 Dec 2009 21:43:05 +0100 Message-ID: <4e5e476b0912081243ra071947if9a3edae77fb3861@mail.gmail.com> Subject: Re: [PATCH] cfq-iosched: reduce write depth only if sync was delayed From: Corrado Zoccolo To: Jeff Moyer Cc: Linux-Kernel , Jens Axboe , Vivek Goyal Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by alpha.home.local id nB8KhU16031103 Content-Length: 7717 Lines: 6 On Tue, Dec 8, 2009 at 1:07 AM, Jeff Moyer wrote:> Corrado Zoccolo writes:>>> Hi Jeff, I remember you saw large performance drop on your SAN for>> sequential writes with low_latency=1.  Can you test if Shaohua's and>> this patch fix allow to recover some bandwidth?  I think that enabling>> the queue depth ramp up only if a sync request was delayed should>> disable it for fast hardware like yours, so you should not be seeing>> the slowdown any more.>> Average of 10 runs.  Low latency set to 0:>> Unit information> ================> File size = megabytes> Blk Size  = bytes> Rate      = megabytes per second> CPU%      = percentage of CPU used during the test> Latency   = milliseconds> Lat%      = percent of requests that took longer than X seconds> CPU Eff   = Rate divided by CPU% - throughput per cpu load>> Sequential Reads>                              File  Blk   Num                   Avg      Maximum      Lat%     Lat%    CPU> Identifier                    Size  Size  Thr   Rate  (CPU%)  Latency    Latency      >2s      >10s    Eff> ---------------------------- ------ ----- ---  ------ ------ --------- -----------  -------- -------- -----> 2.6.32                        8192  65536   8   90.08 94.51%    51.316    10268.25   0.00000  0.00000    95> 2.6.32                        8192  65536  16   99.36 199.8%    89.248    13883.81   0.00000  0.00000    50>> Random Reads>                              File  Blk   Num                   Avg      Maximum      Lat%     Lat%    CPU> Identifier                    Size  Size  Thr   Rate  (CPU%)  Latency    Latency      >2s      >10s    Eff> ---------------------------- ------ ----- ---  ------ ------ --------- -----------  -------- -------- -----> 2.6.32                        8192  65536   8   81.16 85.90%    45.672     5963.19   0.00000  0.00000    94> 2.6.32                        8192  65536  16  116.32 230.3%    58.371     6098.36   0.00000  0.00000    51>> Sequential Writes>                              File  Blk   Num                   Avg      Maximum      Lat%     Lat%    CPU> Identifier                    Size  Size  Thr   Rate  (CPU%)  Latency    Latency      >2s      >10s    Eff> ---------------------------- ------ ----- ---  ------ ------ --------- -----------  -------- -------- -----> 2.6.32                        8192  65536   8  112.17 1085.%    42.623    17114.54   0.00152  0.00000    10> 2.6.32                        8192  65536  16  111.26 2117.%    84.964    26480.60   0.03202  0.00000     5>> Random Writes>                              File  Blk   Num                   Avg      Maximum      Lat%     Lat%    CPU> Identifier                    Size  Size  Thr   Rate  (CPU%)  Latency    Latency      >2s      >10s    Eff> ---------------------------- ------ ----- ---  ------ ------ --------- -----------  -------- -------- -----> 2.6.32                        8192  65536   8  162.48 887.1%     6.106      313.54   0.00000  0.00000    18> 2.6.32                        8192  65536  16  156.38 1767.%    14.077     1254.62   0.00000  0.00000     9>>> Average of 10 runs.  Low latency set to 1:>> Unit information> ================> File size = megabytes> Blk Size  = bytes> Rate      = megabytes per second> CPU%      = percentage of CPU used during the test> Latency   = milliseconds> Lat%      = percent of requests that took longer than X seconds> CPU Eff   = Rate divided by CPU% - throughput per cpu load>> Sequential Reads>                              File  Blk   Num                   Avg      Maximum      Lat%     Lat%    CPU> Identifier                    Size  Size  Thr   Rate  (CPU%)  Latency    Latency      >2s      >10s    Eff> ---------------------------- ------ ----- ---  ------ ------ --------- -----------  -------- -------- -----> 2.6.32                        8192  65536   8   92.23 100.1%    52.119     6920.18   0.00000  0.00000    92> 2.6.32                        8192  65536  16   97.88 217.0%    99.691     7453.18   0.00000  0.00000    45>> Random Reads>                              File  Blk   Num                   Avg      Maximum      Lat%     Lat%    CPU> Identifier                    Size  Size  Thr   Rate  (CPU%)  Latency    Latency      >2s      >10s    Eff> ---------------------------- ------ ----- ---  ------ ------ --------- -----------  -------- -------- -----> 2.6.32                        8192  65536   8   98.70 107.5%    42.994     3409.08   0.00000  0.00000    92> 2.6.32                        8192  65536  16  140.41 323.9%    59.616     4525.46   0.00000  0.00000    43>> Sequential Writes>                              File  Blk   Num                   Avg      Maximum      Lat%     Lat%    CPU> Identifier                    Size  Size  Thr   Rate  (CPU%)  Latency    Latency      >2s      >10s    Eff> ---------------------------- ------ ----- ---  ------ ------ --------- -----------  -------- -------- -----> 2.6.32                        8192  65536   8  112.33 1076.%    42.617    17072.28   0.00076  0.00000    10> 2.6.32                        8192  65536  16  111.84 2097.%    85.156    28221.77   0.02976  0.00000     5>> Random Writes>                              File  Blk   Num                   Avg      Maximum      Lat%     Lat%    CPU> Identifier                    Size  Size  Thr   Rate  (CPU%)  Latency    Latency      >2s      >10s    Eff> ---------------------------- ------ ----- ---  ------ ------ --------- -----------  -------- -------- -----> 2.6.32                        8192  65536   8  159.33 870.5%     6.469      765.50   0.00000  0.00000    18> 2.6.32                        8192  65536  16  141.60 1632.%    15.364     2337.57   0.00000  0.00000     9>>> Cheers,> Jeff> The numbers look good. Now, there is no penalty in having low_latencyset for sequential writes, and just a small penalty for random ones.The fact that random reads are faster with low_latency set is interesting.Is the test is running with your patched tiobench (so that the numberof random operations is comparable with sequential ones)? Thanks,Corrado -- __________________________________________________________________________ dott. Corrado Zoccolo mailto:czoccolo@gmail.comPhD - Department of Computer Science - University of Pisa, Italy--------------------------------------------------------------------------The self-confidence of a warrior is not the self-confidence of the averageman. The average man seeks certainty in the eyes of the onlooker and callsthat self-confidence. The warrior seeks impeccability in his own eyes andcalls that humbleness. Tales of Power - C. 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