Messages in this thread | | | Subject | Re: [PATCH 0/5] make slab gfp fair | From | Peter Zijlstra <> | Date | Mon, 14 May 2007 18:10:11 +0200 |
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On Mon, 2007-05-14 at 08:53 -0700, Christoph Lameter wrote: > On Mon, 14 May 2007, Peter Zijlstra wrote: > > > In the interest of creating a reserve based allocator; we need to make the slab > > allocator (*sigh*, all three) fair with respect to GFP flags. > > I am not sure what the point of all of this is. > > > That is, we need to protect memory from being used by easier gfp flags than it > > was allocated with. If our reserve is placed below GFP_ATOMIC, we do not want a > > GFP_KERNEL allocation to walk away with it - a scenario that is perfectly > > possible with the current allocators. > > Why does this have to handled by the slab allocators at all? If you have > free pages in the page allocator then the slab allocators will be able to > use that reserve.
Yes, too freely. GFP flags are only ever checked when you allocate a new page. Hence, if you have a low reaching alloc allocating a slab page; subsequent non critical GFP_KERNEL allocs can fill up that slab. Hence you would need to reserve a slab per object instead of the normal packing.
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