Re: [PATCH 0/5] make slab gfp fair

Christoph Lameter
2007-05-17T18:02:59Z

On Thu, 17 May 2007, Matt Mackall wrote:

> Simply stated, the problem is sometimes it's impossible to free memory
> without allocating more memory. Thus we must keep enough protected
> reserve that we can guarantee progress. This is what mempools are for
> in the regular I/O stack. Unfortunately, mempools are a bad match for
> network I/O.
>
> It's absolutely correct that performance doesn't matter in the case
> this patch is addressing. All that matters is digging ourselves out of
> OOM. The box either survives the crisis or it doesn't.

Well we fail allocations in order to do so and these allocations may be
even nonatomic allocs. Pretty dangerous approach.

> It's also correct that we should hardly ever get into a situation
> where we trigger this problem. But such cases are still fairly easy to
> trigger in some workloads. Swap over network is an excellent example,
> because we typically don't start swapping heavily until we're quite
> low on freeable memory.

Is it not possible to avoid failing allocs? Instead put processes to
sleep? Run synchrononous reclaim?