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Date: Wed, 27 May 2020 15:44:55 -0400 From: Johannes Weiner <hannes@...xchg.org> To: Roman Gushchin <guro@...com> Cc: Andrew Morton <akpm@...ux-foundation.org>, Christoph Lameter <cl@...ux.com>, Michal Hocko <mhocko@...nel.org>, Shakeel Butt <shakeelb@...gle.com>, linux-mm@...ck.org, Vlastimil Babka <vbabka@...e.cz>, kernel-team@...com, linux-kernel@...r.kernel.org Subject: Re: [PATCH v4 04/19] mm: slub: implement SLUB version of obj_to_index() On Tue, May 26, 2020 at 02:42:12PM -0700, Roman Gushchin wrote: > This commit implements SLUB version of the obj_to_index() function, > which will be required to calculate the offset of obj_cgroup in the > obj_cgroups vector to store/obtain the objcg ownership data. > > To make it faster, let's repeat the SLAB's trick introduced by > commit 6a2d7a955d8d ("[PATCH] SLAB: use a multiply instead of a > divide in obj_to_index()") and avoid an expensive division. > > Vlastimil Babka noticed, that SLUB does have already a similar > function called slab_index(), which is defined only if SLUB_DEBUG > is enabled. The function does a similar math, but with a division, > and it also takes a page address instead of a page pointer. > > Let's remove slab_index() and replace it with the new helper > __obj_to_index(), which takes a page address. obj_to_index() > will be a simple wrapper taking a page pointer and passing > page_address(page) into __obj_to_index(). > > Signed-off-by: Roman Gushchin <guro@...com> > Reviewed-by: Vlastimil Babka <vbabka@...e.cz> Acked-by: Johannes Weiner <hannes@...xchg.org>
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