Re: cache limit

[Denis Vlasenko]

On 19 August 2003 07:39, Anthony R. wrote:
> I would like to tune my kernel not to use as much memory for cache
> as it currently does. I have 2GB RAM, but when I am running one program
> that accesses a lot of files on my disk (like rsync), that program uses
> most of the cache, and other programs wind up swapping out. I'd prefer to
> have just rsync run slower because less of its data is cached, rather
> than have
> all my other programs run more slowly. rsync is not allocating memory,
> but the kernel is caching it at the expense of other programs.

There was a discussion (and patches) in the middle of 2.5 series
about O_STREAMING open flag which mean "do not aggressively cache
this file". Targeted at MP3/video playing, copying large files and such.

I don't know whether it actually was merged. If it was,
your program can use it.
 
> With 2GB on a system, I should never page out, but I consistently do and I
> need to tune the kernel to avoid that. Cache usage is around 1.4 GB!

So why did you configured your system to have huge swap?
That's rather contradictory setup ;)

> I never had this problem with earlier kernels. I've read a lot of comments
> where so-called experts poo-poo this problem, but it is real and
> repeatable and I am
> ready to take matters into my own hands to fix it. I am told the cache
> is replaced when
> another program needs more memory, so it shouldn't swap, but that is not
> the
> behaviour I am seeing.
> 
> Can anyone help point me in the right direction?

I'd say stop allocating insane amounts of swap.
Frankly, with 2G you may run without swap at all.
--
vda
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