Re: [PATCH 16/16] mm/slab: introduce new slab management type, OBJFREELIST_SLAB
From: Vlastimil Babka <hidden>
Date: 2016-01-29 15:21:35
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On 01/28/2016 05:51 AM, Joonsoo Kim wrote:
On Wed, Jan 27, 2016 at 02:35:04PM +0100, Vlastimil Babka wrote:quoted
On 01/14/2016 06:24 AM, Joonsoo Kim wrote:quoted
In fact, I tested another idea implementing OBJFREELIST_SLAB with extendable linked array through another freed object. It can remove memory waste completely but it causes more computational overhead in critical lock path and it seems that overhead outweigh benefit. So, this patch doesn't include it.Can you elaborate? Do we actually need an extendable linked array? Why not just store the pointer to the next free object into the object, NULL for the last one? I.e. a singly-linked list. We should never need to actually traverse it?As Christoph explained, it's the way SLUB manages freed objects. In SLAB case, it doesn't want to touch object itself. It's one of main difference between SLAB and SLUB. These objects are cache-cold now so touching object itself could cause more cache footprint.
Hm I see. Although I wouldn't bet on whether the now-freed object is more or less cold than the freelist array itself (regardless of its placement) :) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>