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

Christoph Lameter
2007-05-14T20:06:19Z

On Mon, 14 May 2007, Peter Zijlstra wrote:

> > Hmmm.. Maybe we could do that.... But what I had in mind was simply to
> > set a page flag (DebugSlab()) if you know in alloc_slab that the slab
> > should be only used for emergency allocation. If DebugSlab is set then the
> > fastpath will not be called. You can trap all allocation attempts and
> > insert whatever fancy logic you want in the debug path since its not
> > performance critical.
>
> I might have missed some detail when I looked at SLUB, but I did not see
> how setting SlabDebug would trap subsequent allocations to that slab.

Ok its not evident in slab_alloc. But if SlabDebug is set then
page->lockless_list is always NULL and we always fall back to
__slab_alloc. There we check for SlabDebug and go to the debug: label.
There you can insert any fancy processing you want.