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

[Christoph Lameter]

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?

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/