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SubjectRe: [2.4.17/18pre] VM and swap - it's really unusable
Stephan von Krawczynski wrote:

[...]

>>If you have applications, which doesn't
>>access to much memory, you can't view the problems.
>>If you access more than 1G (and you do not just copy, but rsync e.g.)
>>and you have only 512MB of RAM, the machine swaps a lot with most actual
>>2.4.-kernels (patches).
>>
>
> Can you provide a simple and reproducible test case (e.g. some demo source),
> where things break? I am very willing to test it here.
>

It's easy - take a grown inn-newsserver-partition with reiserfs (*) (a
lot of small files and a lot of directories), about 1,3 GB or more, and
do a complete rsync to this partition to transport it somewhere else.
But you have to do it with a existing target, no empty target, so that
rsync must scan the whole target partition, too.

I don't like special test-programs. They seldom show up the reality.
What we need is a kernel that behaves fine in reality - not in testcases.
And before starting the test, take care, that most of ram is already
used for cache or buffers or applications.

I did this test with several VM-patches and there are huge differences
in swap consumption between them: 319MB with 2.4.17rc2 and 59MB with
2.4.17 oom-patch (max).
It's more than a little difference :-).


Regards,
Andreas Hartmann


(*) If I had DSL, I would send it to you (as tar.gz) - but with modem,
it's a bit too much :-)!
But your squid cache should be fine, too. It has a similar structure: a
lot of small files and a lot of subdirectories. But I think, that your
squid cache size isn't as high as my inn-partition.

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