Linux-kernel mailing list archive 2000-06,: Re: 2.2.x Memory subsystem questions

# Re: 2.2.x Memory subsystem questions

Andrea Arcangeli (andrea@suse.de)
Mon, 7 Feb 2000 01:52:59 +0100 (CET)

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On Wed, 19 Jan 2000, Mike Panetta wrote:

>Is there any way to get the 2.2.x kernels to have memory subsystem
>performance similer to the 2.0.x kernels in low memory situations?

You may want to try this patch on the top of 2.2.14:

ftp://ftp.*.kernel.org/pub/linux/kernel/people/andrea/kernels/v2.2/2.2.14aa6.gz

The system should stop to swapout then. After that you probably also want
to tune by hand the VM checking the performance difference after executing
something like this:

echo 10 > /proc/sys/vm/pagecache
echo 10 > /proc/sys/vm/buffermem

(try also with 5 or 20, it mainly depends on what you are doing with the
machine...) A value of 10 will forbid the VM to shrink the buffer cache
and the page cache to less than 1.6mbyte. Thus you will lock in memory
3.2mbyte of ram with such defaults but you'll also know that you won't
have to pagein for such 3.2mbyte of ram (you'll keep such information in
cache ;). This by hand tuning is necessary only because the swapout
behaviour in the VM is not smart enough in 2.2.x. I know how to make the
VM smart enough (it's not very far from the point I just reach in the
current 2.3.x). The other part that I have not yet implemented in the
2.3.x SMP threaded version, would be interesting only if you swapout all
the time because you really haven't enough memory to run thus it's not
high prio for now. Nevertheless I'll try to implement that as soon as I'll
find the time ;).

Andrea

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