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Date: Tue, 17 Mar 2009 11:34:00 -0700 From: Pekka Enberg <penberg@...helsinki.fi> To: Christoph Lameter <cl@...ux-foundation.org> Cc: Nitin Gupta <ngupta@...are.org>, linux-kernel@...r.kernel.org Subject: Re: [PATCH 2/3]: xvmalloc memory allocator On Tue, 17 Mar 2009, Nitin Gupta wrote: >> Creating slabs for sizes in range, say, [32, 3/4*PAGE_SIZE] separated by >> 64bytes >> will require 48 slabs! Then for slab of each size class will have wastage >> due to >> unused slab objects in each class. >> Larger difference in slab sizes (and thus small no. of them), will surely >> cause too much >> wastage due to internal fragmentation. On Tue, Mar 17, 2009 at 10:58 AM, Christoph Lameter <cl@...ux-foundation.org> wrote: > The slabs that match existing other slabs of similar sizes will be aliased > and not created. Create the 48 slabs and you likely will only use 10 real > additional ones. The rest will just be pointing to existing ones. Yup. One thing I don't quite understand is why you need all the 48 caches in the first place. Allocation sizes tend to be clustered and I would have imagined you'd see that when compressing page sized chunks as well. Using kmemtrace to analyze the exact reason for the bad fragmentation would probably be helpful. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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