Re: [PATCH 02/10] mm: system wide ALLOC_NO_WATERMARK

Peter Zijlstra
2007-08-06T19:33:23Z

On Mon, 2007-08-06 at 12:11 -0700, Christoph Lameter wrote:
> On Mon, 6 Aug 2007, Peter Zijlstra wrote:
>
> > > > Shudder. That can just be a desaster for NUMA. Both performance wise
> > > > and logic wise. One cpuset being low on memory should not affect
> > > > applications in other cpusets.
> >
> > Do note that these are only PF_MEMALLOC allocations that will break the
> > cpuset. And one can argue that these are not application allocation but
> > system allocations.
>
> This is global, global locking etc etc. On a large NUMA system this will
> cause significant delays. One fears that a livelock may result.

The only new lock is in SLUB, and I'm not aware of any regular
PF_MEMALLOC paths using slab allocations, but I'll instrument the
regular reclaim path to verify this.

The functionality this is aimed at is swap over network, and I doubt
you'll be enabling that on these machines.