Re: [15/17] SLUB: Support virtual fallback via SLAB_VFALLBACK
From: Nick Piggin
Date: Sun Sep 30 2007 - 16:47:50 EST
On Monday 01 October 2007 06:12, Andrew Morton wrote:
> On Sun, 30 Sep 2007 05:09:28 +1000 Nick Piggin <nickpiggin@xxxxxxxxxxxx>
> > On Sunday 30 September 2007 05:20, Andrew Morton wrote:
> > > We can't "run out of unfragmented memory" for an order-2 GFP_KERNEL
> > > allocation in this workload. We go and synchronously free stuff up to
> > > make it work.
> > >
> > > How did this get broken?
> > Either no more order-2 pages could be freed, or the ones that were being
> > freed were being used by something else (eg. other order-2 slab
> > allocations).
> No. The current design of reclaim (for better or for worse) is that for
> order 0,1,2 and 3 allocations we just keep on trying until it works. That
> got broken and I think it got broken at a design level when that
> did_some_progress logic went in. Perhaps something else we did later
> worsened things.
It will keep trying until it works. It won't have stopped trying (unless
I'm very mistaken?), it's just oom killing things merrily along the way.
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