Messages in this thread | | | Subject | Re: [PATCH 0/5] make slab gfp fair | From | Peter Zijlstra <> | Date | Wed, 16 May 2007 23:04:54 +0200 |
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On Wed, 2007-05-16 at 13:59 -0700, Christoph Lameter wrote: > On Wed, 16 May 2007, Peter Zijlstra wrote: > > > > I do not see any distinction between DMA and regular memory. If we need > > > DMA memory to complete the transaction then this wont work? > > > > If network relies on slabs that are cpuset constrained and the page > > allocator reserves do not match that, then yes, it goes bang. > > So if I put a 32 bit network card in a 64 bit system -> bang?
I hope the network stack already uses the appropriate allocator flags. If the slab was GFP_DMA that doesn't change, the ->reserve_slab will still be GFP_DMA.
> > > Is there some indicator somewhere that indicates that we are in trouble? I > > > just see the ranks. > > > > Yes, and page->rank will only ever be 0 if the page was allocated with > > ALLOC_NO_WATERMARKS, and that only ever happens if we're in dire > > straights and entitled to it. > > > > Otherwise it'll be ALLOC_WMARK_MIN or somesuch. > > How we know that we are out of trouble? Just try another alloc and see? If > that is the case then we may be failing allocations after the memory > situation has cleared up.
No, no, for each regular allocation we retry to populate ->cpu_slab with a new slab. If that works we're out of the woods and the ->reserve_slab is cleaned up.
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