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Subject: Re: [PATCH 0/3] readahead drop behind and size adjustment
From: Eric St-Laurent <ericstl34@sympatico.ca>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
       Fengguang Wu <fengguang.wu@gmail.com>, Dave Jones <davej@redhat.com>,
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Date: Sun, 29 Jul 2007 03:44:33 -0400
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On Wed, 2007-25-07 at 17:09 +1000, Nick Piggin wrote:
> Eric St-Laurent wrote:
> > I test this on my main system, so patches with basic testing and
> > reasonable stability are preferred. I just want to avoid data corruption
> > bugs. FYI, I used to run the -rt tree most of the time.
> 
> OK here is one which just changes the rate that the active and inactive
> lists get scanned. Data corruption bugs should be minimal ;)
> 

Nick,

I have tried your patch with my test case, unfortunately it doesn't
help.

Numbers did vary a little bit more, and it seemed drop_caches was not
working as well as usual (used between the runs).

Also, overall the runs took about .1s more to complete.


Linux 2.6.23-rc1-nick PREEMPT x86_64

Base test:

1st run: 0m9.123s
2nd run: 0m3.565s
3rd run: 0m3.553s
4th run: 0m3.565s

Reading a large file test:

1st run: 0m9.146s
2nd run: 0m3.560s
`/tmp/large_file' -> `/dev/null'
3rd run: 0m19.759s
4th run: 0m3.515s

Copying (using cp) a large file test:

1st run: 0m9.085s
2nd run: 0m3.522s
`/tmp/large_file' -> `/tmp/large_file.copy'
3rd run: 0m9.977s
4th run: 0m3.518s


Anyway, what is the theory behind the patch?


- Eric