Re: ~500 megs cached yet 2.6.5 goes into swap hell

Brett E.
2004-04-29T18:32:40Z

Horst von Brand wrote:

> "Brett E." <brettspamacct@fastclick.com> said:
>
> [...]
>
>
>>I created a hack which allocates memory causing cache to go down, then
>>exits, freeing up the malloc'ed memory. This brings free memory up by
>>400 megs and brings the cache down to close to 0, of course the cache
>>grows right afterwards. It would be nice to cap the cache datastructures
>>in the kernel but I've been posting about this since September to no
>>avail so my expectations are pretty low.
>
>
> Because it is complete nonsense. Keeping stuff around in RAM in case it
> is needed again, as long as RAM is not needed for anything else, is a mayor
> win. That is what cache is.
The key phrase in your post is "as long as RAM is not needed for
anything else." My assertion was that this is not the case and it seems
to favor cache over pages being used. Sar shows heavy paging to/from
disk even though 500 megs are reported in cache. I hope I don't need to
go into what paging in/out in succession means regarding paging out
pages which we will need shortly after they are paged out. Sar also
reports no swapping, hence the need to figure out why there is a
disprepency before continuing.