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From: Christoph Lameter <cl@linux.com>
To: Bharata B Rao <bharata@linux.ibm.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	linux-mm@kvack.org, David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	guro@fb.com, vbabka@suse.cz, shakeelb@google.com,
	Johannes Weiner <hannes@cmpxchg.org>,
	aneesh.kumar@linux.ibm.com
Subject: Re: [RFC PATCH v0] mm/slub: Let number of online CPUs determine the slub page order
Date: Thu, 21 Jan 2021 10:01:57 +0000 (UTC)	[thread overview]
Message-ID: <alpine.DEB.2.22.394.2101210959060.100764@www.lameter.com> (raw)
In-Reply-To: <20210121053003.GB2587010@in.ibm.com>

On Thu, 21 Jan 2021, Bharata B Rao wrote:

> > The problem is that calculate_order() is called a number of times
> > before secondaries CPUs are booted and it returns 1 instead of 224.
> > This makes the use of num_online_cpus() irrelevant for those cases
> >
> > After adding in my command line "slub_min_objects=36" which equals to
> > 4 * (fls(num_online_cpus()) + 1) with a correct num_online_cpus == 224
> > , the regression diseapears:
> >
> > 9 iterations of hackbench -l 16000 -g 16: 3.201sec (+/- 0.90%)
>
> Should we have switched to num_present_cpus() rather than
> num_online_cpus()? If so, the below patch should address the
> above problem.

There is certainly an initcall after secondaries are booted where we could
redo the calculate_order?

Or the num_online_cpus needs to be up to date earlier. Why does this issue
not occur on x86? Does x86 have an up to date num_online_cpus earlier?



  parent reply	other threads:[~2021-01-21 10:03 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-18  8:27 [RFC PATCH v0] mm/slub: Let number of online CPUs determine the slub page order Bharata B Rao
2020-11-18 11:25 ` Vlastimil Babka
2020-11-18 19:34   ` Roman Gushchin
2020-11-18 19:53     ` David Rientjes
2020-11-18 19:53       ` David Rientjes
2021-01-20 17:36 ` Vincent Guittot
2021-01-20 17:36   ` Vincent Guittot
2021-01-21  5:30   ` Bharata B Rao
2021-01-21  9:09     ` Vincent Guittot
2021-01-21  9:09       ` Vincent Guittot
2021-01-21 10:01     ` Christoph Lameter [this message]
2021-01-21 10:01       ` Christoph Lameter
2021-01-21 10:48       ` Vincent Guittot
2021-01-21 10:48         ` Vincent Guittot
2021-01-21 18:19       ` Vlastimil Babka
2021-01-22  8:03         ` Vincent Guittot
2021-01-22  8:03           ` Vincent Guittot
2021-01-22 12:03           ` Vlastimil Babka
2021-01-22 13:16             ` Vincent Guittot
2021-01-22 13:16               ` Vincent Guittot
2021-01-23  5:16             ` Bharata B Rao
2021-01-23 12:32               ` Vincent Guittot
2021-01-23 12:32                 ` Vincent Guittot
2021-01-25 11:20                 ` Vlastimil Babka
2021-01-26 23:03                   ` Will Deacon
2021-01-27  9:10                     ` Christoph Lameter
2021-01-27  9:10                       ` Christoph Lameter
2021-01-27 11:04                       ` Vlastimil Babka
2021-02-03 11:10                         ` Bharata B Rao
2021-02-04  7:32                           ` Vincent Guittot
2021-02-04  7:32                             ` Vincent Guittot
2021-02-04  9:07                             ` Christoph Lameter
2021-02-04  9:07                               ` Christoph Lameter
2021-02-04  9:33                           ` Vlastimil Babka
2021-02-08 13:41                             ` [PATCH] mm, slub: better heuristic for number of cpus when calculating slab order Vlastimil Babka
2021-02-08 14:54                               ` Vincent Guittot
2021-02-08 14:54                                 ` Vincent Guittot
2021-02-10 14:07                               ` Mel Gorman
2021-01-22 13:05         ` [RFC PATCH v0] mm/slub: Let number of online CPUs determine the slub page order Jann Horn
2021-01-22 13:05           ` Jann Horn
2021-01-22 13:09           ` Jann Horn
2021-01-22 13:09             ` Jann Horn
2021-01-22 15:27           ` Vlastimil Babka
2021-01-25  4:28           ` Bharata B Rao
2021-01-26  8:52         ` Michal Hocko
2021-01-26 13:38           ` Vincent Guittot
2021-01-26 13:38             ` Vincent Guittot
2021-01-26 13:59             ` Michal Hocko
2021-01-27 13:38               ` Vlastimil Babka
2021-01-28 13:45               ` Mel Gorman
2021-01-28 13:57                 ` Michal Hocko
2021-01-28 14:42                   ` Mel Gorman

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