Re: VM patches in 2.6.4-rc1-mm2

Nick Piggin
2004-03-10T08:36:40Z

Mike Fedyk wrote:

> Andrew Morton wrote:
>
>> Mike Fedyk <mfedyk@matchmail.com> wrote:
>>
>>> Most of the previous 2.6 kernels I was running on these servers
>>> would be lightly hitting swap by now. This definitely looks better
>>> to me.
>>
>>
>>
>> It sounds worse to me. "Lightly hitting swap" is good. It gets rid
>> of stuff,
>> freeing up physical memory.
>
>
> Andrew, it looks like you're right. This[1] server doesn't seem to be
> hitting swap enough. But my other[2] file server is doing great with
> it on the other hand (though, it hasn't swapped at all).
>

Just curious, what makes you say [1] isn't hitting swap enough and [2]
is OK? The graphs are better now, by the way. Thank you.

> Maybe a little tuning is in order?
>
> Any patches I should try?
>

Mainline doesn't put enough pressure on slab with highmem systems. This
creates a lot more ZONE_NORMAL pressure and that causes swapping.

Now with the 2.6 VM, you don't do any mapped memory scaning at all
while you only have a small amount of memory pressure. This means that
truely inactive mapped pages never get reclaimed.

The patches you are using do not address this. My split active list
patches should do so. Alternatively you can increase
/proc/sys/vm/swappiness, but that isn't a complete solution, and might
make things too swappy. It is a difficult beast to control.