linux-kernel - Re: [patch] Give kjournald a IOPRIO_CLASS

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Message-ID: <2c0942db0711161035x5978a37bjd0f3fb67470553eb@mail.gmail.com>
Date:	Fri, 16 Nov 2007 10:35:25 -0800
From:	"Ray Lee" <ray-lk@...rabbit.org>
To:	"Alan D. Brunelle" <alan.brunelle@...com>
Cc:	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Rik van Riel" <riel@...hat.com>, arjan@...radead.org,
	jens.axboe@...cle.com, mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: Re: [patch] Give kjournald a IOPRIO_CLASS_RT io priority

On Nov 16, 2007 8:25 AM, Alan D. Brunelle <alan.brunelle@...com> wrote:
> Here are the results for the latest tests, some notes:
>
> o  The machine actually has 8GiB of RAM, so the tests still may end up
> using (some) page cache. (But at least it was the same for both kernels!
> :-) )
>
> o  Sorry the results took so long - the updated tree size caused the
> runs to take > 12 hours...
>
> o  The longer runs seemed to bring down the standard deviation a bit,
> although they are still quite large.
>
> o  10 runs per test (read large file, read a tree, overwrite large
> file), with averages presented.
>
> o  1st 4 columns (min, avg, max, std dev) refer to the average run
> lengths for the tests - real time, in seconds
>
> o  The last 3 columns are extracted from iostat results over the course
> of the whole run.
>
> o  The read a tree test certainly stands out - the other 2 large file
> manipulations have the two kernels within a couple of percent, but the
> read a tree test has Arjan's patch taking about 47%(!) longer on
> average. The increased %iowait & %system time in all 3 cases is interesting.
>
>
> Read large file:
>
> Kernel  Min    Avg    Max   Std Dev    %user  %system  %iowait
> --------------------------------------------------------------
> base :  201.6  215.1  275.5   22.8     0.26%    4.69%   33.54%
> arjan:  198.0  210.3  261.5   18.5     0.33%   10.24%   54.00%
>
> Read a tree:
>
> Kernel  Min    Avg    Max   Std Dev    %user  %system  %iowait
> --------------------------------------------------------------
> base : 3518.2 4631.3 5991.3  784.6     0.19%    3.29%   23.56%
> arjan: 5731.6 6849.8 7777.4  731.6     0.32%    9.90%   52.70%
>
> Overwrite large file:
>
> Kernel  Min    Avg    Max   Std Dev    %user  %system  %iowait
> --------------------------------------------------------------
> base :  104.2  147.7  239.5   38.4      0.02%    0.05%   1.08%
> arjan:  106.2  149.7  239.2   38.4      0.25%    0.79%  14.97%
>
> Let me know if there is anything else I can do to elaborate, or if you
> have suggestions for further testing.

Out of curiosity, what are the mount options for the freshly created
ext3 fs? In particular, are you using noatime, nodiratime?

Ray
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