Re: Random file I/O regressions in 2.6 [patch+results]

[Alexey Kopytov]

On Saturday 22 May 2004 01:13, Alexey Kopytov wrote:
>I ran the tests with a configuration as close to yours as possible. Here are
>the results for mem=256M, 2G total file size (ext3):
>
>2.4.25:
>       Time spent for test:  79.4146s
>                0.20user 16.08system 3:20.29elapsed 8%CPU
>       Time spent for test:  78.9797s
>                0.11user 15.84system 3:19.76elapsed 7%CPU
>
>2.6.6-bk, AS:
>       Time spent for test:  81.2208s
>                0.13user 17.97system 3:13.30elapsed 9%CPU
>       Time spent for test:  82.5538s
>                0.14user 18.00system 3:14.88elapsed 9%CPU
>
>This correlates very well your results. But when I returned back to my
>original configuration (mem=640M, 3G total file size), I got the following:
>
>2.4.25:
>       Time spent for test:  77.5377s
>
>2.6.6-bk, AS:
>       Time spent for test:  83.1929s
>
>It seems like the smaller file size just hides the regression, but I have to
>run some more tests to ensure this.
>

The assumption appears to be true. I tried to vary the total file size and got 
the following results (tests were done on another IDE disk):

2.4.27-pre3:
    2 GB:  58.2707s
    4 GB:  72.3313s
    8 GB:  83.082s

2.6.7-rc1, AS:
    2 GB:  60.6792s  
    4 GB:  82.8023s
    8 GB:  99.4398s

Varying the number of files while keeping the total file size constant also 
gives some interesting results:

2.4.27-pre3, 4 GB total file size:
    1 file:  71.7288s
    128 files: 72.3313s
    256 files: 73.9268

2.6.7-rc1, AS, 4 GB total file size:
    1 file: 76.443
    128 files: 82.8023
    256 files: 81.9618

-- 
Alexey Kopytov, Software Developer
MySQL AB, www.mysql.com

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