Re: inode/dentry pressure

[Jeff Garzik <jgarzik@mandrakesoft.com>]

Rik van Riel wrote:
> since the inode and dentry cache memory usage and the way this
> memory is reaped by kswapd are still very fragile and these
> caches often eat as much as 50% of system memory on normal
> desktop systems I think we need to come up with a real solution
> to this problem.
> 
> A quick fix would be to always try and reap inode and dentry
> cache memory whenever these two eat over 10% of memory and let
> the normal VM path eat from them when they're consuming less,
> but since this could break in other situations I'm asking here
> if anybody else has a real solution...
> 
> If we cannot find an easy to implement Real Solution(tm) we
> should probably go for the 10% limit in 2.4 and implement the
> real solution in 2.5; if anybody has a 2.4-attainable idea
> I'd like to hear about it ;)

IMHO this is more of a policy question, though I agree strongly it needs
some sort of answer.

When applications start competing with disposable OS caches, of all
sorts, you have to decide cache reap rate, and a suitable low water mark
for each cache in order for the system to be useable under heavy load. 
Some caches are going to have a higher low-water mark than others; some
caches may need to be reaped more slowly due to various issues.

-- 
Jeff Garzik      | Game called on account of naked chick
Building 1024    |
MandrakeSoft     |
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