Messages in this thread | | | Subject | Re: [PATCH 12/30] mm: memory reserve management | From | Peter Zijlstra <> | Date | Mon, 28 Jul 2008 19:13:43 +0200 |
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On Mon, 2008-07-28 at 11:49 -0500, Matt Mackall wrote: > On Mon, 2008-07-28 at 13:06 +0300, Pekka Enberg wrote: > > We're trying to get rid of kfree() so I'd __kfree_reserve() could to > > mm/sl?b.c. Matt, thoughts? > > I think you mean ksize there. My big issue is that we need to make it > clear that ksize pairs -only- with kmalloc and that > ksize(kmem_cache_alloc(...)) is a categorical error. Preferably, we do > this by giving it a distinct name, like kmalloc_size(). We can stick an > underbar in front of it to suggest you ought not be using it too.
Right, both make sense, so _kmalloc_size() has my vote.
> > > + /* > > > + * ksize gives the full allocated size vs the requested size we > > used to > > > + * charge; however since we round up to the nearest power of two, > > this > > > + * should all work nicely. > > > + */ > > SLOB doesn't do this, of course. But does that matter? I think you want > to charge the actual allocation size to the reserve in all cases, no? > That probably means calling ksize() on both alloc and free.
Like said, I still need to do all the SLOB reservation stuff. That includes coming up with upper bound fragmentation loss.
For SL[UA]B I use roundup_power_of_two for kmalloc sizes. Thus with the above ksize(), if we did p=kmalloc(x), then we'd account roundup_power_of_two(x), and that should be equal to roundup_power_of_two(ksize(p)), as ksize will always be smaller or equal to the roundup.
I'm guessing the power of two upper bound is good for SLOB too - although I haven't tried proving it wrong or tighetening it.
Only the kmem_cache_* reservation stuff would need some extra attention with SLOB.
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