From: Hyeonggon Yoo <42.hyeyoo@gmail.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>
Subject: Almost no difference
Date: Sat, 9 Oct 2021 11:45:54 +0000 [thread overview]
Message-ID: <20211009114554.GA8165@kvm.asia-northeast3-a.c.our-ratio-313919.internal> (raw)
In-Reply-To: <YWDjZ+KlkV2wKShh@casper.infradead.org>
On Sat, Oct 09, 2021 at 01:33:43AM +0100, Matthew Wilcox wrote:
> On Sat, Oct 09, 2021 at 12:19:03AM +0000, Hyeonggon Yoo wrote:
> > - Is there a reason that SLUB does not implement cache coloring?
> > it will help utilizing hardware cache. Especially in block layer,
> > they are literally *squeezing* its performance now.
>
> Have you tried turning off cache colouring in SLAB and seeing if
> performance changes? My impression is that it's useful for caches
> with low associativity (direct mapped / 2-way / 4-way), but loses
> its effectiveness for caches with higher associativity. For example,
> my laptop:
>
> L1 Data Cache: 48KB, 12-way associative, 64 byte line size
> L1 Instruction Cache: 32KB, 8-way associative, 64 byte line size
> L2 Unified Cache: 1280KB, 20-way associative, 64 byte line size
> L3 Unified Cache: 12288KB, 12-way associative, 64 byte line size
>
> I very much doubt that cache colouring is still useful for this machine.
On my machine,
L1 Data Cache: 32KB, 8-way associative, 64 byte line size
L1 Instruction Cache: 32KB, 8-way associative, 64 byte line size
L2 Unified Cache: 1MB, 16-way associative, 64 byte line size
L3 Unified Cache: 33MB, 11-way associative, 64 byte line size
I run hackbench with per-node coloring, per-cpu coloring, and without
coloring.
hackbench -g 100 -l 200000
without coloring: 2196.787
with per-node coloring: 2193.607
with per-cpu coloring: 2198.076
it seems there is almost no difference.
How much difference did you seen low associativity processors?
Hmm... I'm gonna search if there's related paper.
next prev parent reply other threads:[~2021-10-09 11:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-09 0:19 [RFC] Some questions and an idea on SLUB/SLAB Hyeonggon Yoo
2021-10-09 0:33 ` Matthew Wilcox
2021-10-09 0:40 ` Hyeonggon Yoo
2021-10-09 11:45 ` Hyeonggon Yoo [this message]
2021-10-11 7:13 ` Christoph Lameter
2021-10-13 3:44 ` Hyeonggon Yoo
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