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Date:   Mon, 03 Jul 2023 12:33:25 +0200
Message-Id: <CTSGWINSM18Q.3HQ1DN27GNA1R@imme>
Cc:     "Christoph Lameter" <cl@linux.com>,
        "Lameter, Christopher" <cl@os.amperecomputing.com>,
        "Pekka Enberg" <penberg@kernel.org>,
        "Joonsoo Kim" <iamjoonsoo.kim@lge.com>,
        "Andrew Morton" <akpm@linux-foundation.org>,
        "Vlastimil Babka" <vbabka@suse.cz>,
        "Roman Gushchin" <roman.gushchin@linux.dev>,
        "Hyeonggon Yoo" <42.hyeyoo@gmail.com>, <linux-mm@kvack.org>,
        "Jonathan Corbet" <corbet@lwn.net>, <linux-doc@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>,
        "Matthew Wilcox" <willy@infradead.org>,
        "Kees Cook" <keescook@chromium.org>,
        "Rafael Aquini" <aquini@redhat.com>
Subject: Re: [PATCH v2] mm/slub: disable slab merging in the default
 configuration
From:   "Julian Pidancet" <julian.pidancet@oracle.com>
To:     "David Rientjes" <rientjes@google.com>
References: <20230629221910.359711-1-julian.pidancet@oracle.com>
 <38083ed2-333b-e245-44e4-2f355e4f9249@google.com>
In-Reply-To: <38083ed2-333b-e245-44e4-2f355e4f9249@google.com>
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On Mon Jul 3, 2023 at 02:09, David Rientjes wrote:
> I think we need more data beyond just kernbench.  Christoph's point about=
=20
> different page sizes is interesting.  In the above results, I don't know=
=20
> the page orders for the various slab caches that this workload will=20
> stress.  I think the memory overhead data may be different depending on=
=20
> how slab_max_order is being used, if at all.
>
> We should be able to run this through a variety of different benchmarks=
=20
> and measure peak slab usage at the same time for due diligence.  I suppor=
t=20
> the change in the default, I would just prefer to know what the=20
> implications of it is.
>
> Is it possible to collect data for other microbenchmarks and real-world=
=20
> workloads?  And perhaps also with different page sizes where this will=20
> impact memory overhead more?  I can help running more workloads once we=
=20
> have the next set of data.
>

David,

I agree about the need to perform those tests on hardware using larger
pages. I will collect data if I have the chance to get my hands on one
of these systems.

Do you have specific tests or workload in mind ? Compiling the kernel
with files sitting on an XFS partition is not exhaustive but it is the
only test I could think of that is both easy to set up and can be=20
reproduced while keeping external interferences as little as possible.

--=20
Julian

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