Bug? in 2.4 memory management...

Bug? in 2.4 memory management...

[José Manuel Román Ramírez]

Hi,
I think we've 'discovered' a bug regarding the kernel 2.4.2-ac11 (and maybe 
other) and the memory management. It seems that the cached memory sometimes 
is not freed as more memory is required. 

The system where we have detected the problem was an athlon 1ghz, 1.2gb of 
ram, and a swapfile of 2gb.

When we run a program that requires/uses 1ghz of memory, and we kill it, all 
(or nearly all) the memory is used by the cache, as we load a hugue file. The 
next time we run the program, it seems like the kernel can't use the cached 
memory and the memory we need is taken from the swap. Note however that when 
we set a swap partition smaller than the memory required, let's say 128mb, 
the problem disappears as the cache memory is used instead the swap...

So, what's wrong? Thanks in advance!

-- 
"I consider Red Hat 7.0 to be basically unusable as a development platform"
Linus Torvalds
--
Jose Manuel Roman - Theuzifan
roman@wol.es - uzi@simauria.upv.es

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Re: Bug? in 2.4 memory management...

[Marcelo Tosatti]

On Wed, 7 Mar 2001, Jose Manuel Roman Ramirez wrote:

> Hi,
> I think we've 'discovered' a bug regarding the kernel 2.4.2-ac11 (and maybe 
> other) and the memory management. It seems that the cached memory sometimes 
> is not freed as more memory is required. 
> 
> The system where we have detected the problem was an athlon 1ghz, 1.2gb of 
> ram, and a swapfile of 2gb.
> 
> When we run a program that requires/uses 1ghz of memory, and we kill it, all 
> (or nearly all) the memory is used by the cache, as we load a hugue file. The 
> next time we run the program, it seems like the kernel can't use the cached 
> memory and the memory we need is taken from the swap. Note however that when 
> we set a swap partition smaller than the memory required, let's say 128mb, 
> the problem disappears as the cache memory is used instead the swap...
> 
> So, what's wrong? Thanks in advance!

VM balance is not quite right. 

Could you please try ac12 (which has a patch to tune the VM a bit) and
report results?

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