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From: Christopher Lameter <cl@linux.com>
To: Wen Yang <wenyang@linux.alibaba.com>
Cc: Pekka Enberg <penberg@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Roman Gushchin <guro@fb.com>,
	Xunlei Pang <xlpang@linux.alibaba.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/slub: improve count_partial() for CONFIG_SLUB_CPU_PARTIAL
Date: Mon, 24 Feb 2020 01:29:09 +0000 (UTC)	[thread overview]
Message-ID: <alpine.DEB.2.21.2002240126190.13486@www.lameter.com> (raw)
In-Reply-To: <20200222092428.99488-1-wenyang@linux.alibaba.com>

On Sat, 22 Feb 2020, Wen Yang wrote:

> We also observed that in this scenario, CONFIG_SLUB_CPU_PARTIAL is turned
> on by default, and count_partial() is useless because the returned number
> is far from the reality.

Well its not useless. Its just not counting the partial objects in per cpu
partial slabs. Those are counted by a different counter it.

> Therefore, we can simply return 0, then nr_free is also 0, and eventually
> active_objects == total_objects. We do not introduce any regression, and
> it's preferable to show the unrealistic uniform 100% slab utilization
> rather than some very high but incorrect value.

I suggest that you simply use the number of partial slabs and multiply
them by the number of objects in a slab and use that as a value. Both
values are readily available via /sys/kernel/slab/<...>/

You dont need a patch to do that.


  reply	other threads:[~2020-02-24  1:29 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-22  9:24 [PATCH] mm/slub: improve count_partial() for CONFIG_SLUB_CPU_PARTIAL Wen Yang
2020-02-24  1:29 ` Christopher Lameter [this message]
2020-02-24  1:29   ` Christopher Lameter
2020-02-24 16:57   ` Roman Gushchin
2020-02-25 15:49     ` Vlastimil Babka
2020-02-26 18:31     ` Christopher Lameter
2020-02-26 18:31       ` Christopher Lameter
2020-02-27 18:35       ` Roman Gushchin
2020-03-03 16:05         ` Christopher Lameter
2020-03-03 16:05           ` Christopher Lameter

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