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

Alexey Kopytov
2004-05-26T04:43:23Z

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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