Re: Pages swapped out even when free memory available...

From: Daniel Egger (
Date: Tue Aug 20 2002 - 09:11:01 EST

Am Die, 2002-08-20 um 12.28 schrieb Jan Hudec:

> Don't do it. In user-land, you simply don't have the info kernel does.
> Gimp tries to do things like this and results are truly horrible.
> It forces machine in deep swap if you set the cache large, while with
> small cache the actual size does not matter much as kernel takes care of
> the real caching.
> You should rather open a file you want to swap in, mmap it and only keep
> minimum data in other memory. Only reason to do even this may be, that
> the data may get too large to fit in swap. For all other reasons you
> should just let kernel do it's work.

Interesting you mention it. A week ago I started a thread exactly for
that reason; I implemented GIMPs tilemanagement using mmap but
unfortunately the performance sucks even more than GIMPs "clever"
swapping. That having said it has at least one more severe disadvantage:
The maximum amount of mmapable memory is far less than the maximum
filesize with large file support.


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