From: Hyeonggon Yoo <42.hyeyoo@gmail.com>
To: Christoph Lameter <cl@gentwo.de>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
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: Re: [PATCH] mm, slub: Use prefetchw instead of prefetch
Date: Mon, 11 Oct 2021 07:32:39 +0000 [thread overview]
Message-ID: <20211011073239.GA63896@kvm.asia-northeast3-a.c.our-ratio-313919.internal> (raw)
In-Reply-To: <alpine.DEB.2.22.394.2110110919050.130815@gentwo.de>
On Mon, Oct 11, 2021 at 09:20:36AM +0200, Christoph Lameter wrote:
> On Fri, 8 Oct 2021, Hyeonggon Yoo wrote:
>
> > It's certain that an object will be not only read, but also
> > written after allocation.
>
> get_freepointer is used in multiple code path not only in allocation. It
> is for example used when scanning through a freelist.
>
> With this change all objects get needlessly dirtied and the cross cpu
> cache contention is increased.
I didn't touch get_freepointer and there's
only one caller of prefetch_freepointer.
My change was not adding additional prefetch on get_freepointer,
but changing existing prefetch into prefetchw.
The prefetch was introcued by commit 0ad9500e16fe ("slub: prefetch next
freelist pointer in slab_alloc()") that you ACKed in 2011.
Do you think removeing existing prefetch is better than changing it
from prefetch to prefetchw?
prev parent reply other threads:[~2021-10-11 7:32 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-08 13:36 [PATCH] mm, slub: Use prefetchw instead of prefetch Hyeonggon Yoo
2021-10-10 22:49 ` David Rientjes
2021-10-11 7:21 ` Vlastimil Babka
2021-10-11 10:33 ` Perf and Hackbench results on my machine Hyeonggon Yoo
2021-10-11 13:49 ` Hyeonggon Yoo
2021-10-11 7:23 ` [PATCH] mm, slub: Use prefetchw instead of prefetch Hyeonggon Yoo
2021-10-11 7:20 ` Christoph Lameter
2021-10-11 7:32 ` Hyeonggon Yoo [this message]
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