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Sun, 09 Jul 2023 19:40:40 -0700 (PDT) Date: Sun, 9 Jul 2023 19:40:39 -0700 (PDT) From: David Rientjes To: Julian Pidancet cc: Christoph Lameter , "Lameter, Christopher" , Pekka Enberg , Joonsoo Kim , Andrew Morton , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org, Jonathan Corbet , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Matthew Wilcox , Kees Cook , Rafael Aquini Subject: Re: [PATCH v2] mm/slub: disable slab merging in the default configuration In-Reply-To: <3bcfa538-4474-09b7-1812-b4260b09256a@google.com> Message-ID: <7b6b07b3-d8a1-b24f-1df2-bf6080bc5516@google.com> References: <20230629221910.359711-1-julian.pidancet@oracle.com> <38083ed2-333b-e245-44e4-2f355e4f9249@google.com> <8813897d-4a52-37a0-fe44-a9157716be9b@google.com> <17349901-df3a-494e-fa71-2584d92526b5@google.com> <3bcfa538-4474-09b7-1812-b4260b09256a@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspam-User: X-Stat-Signature: wgzhqa7d8zt69zzy6m6ira3din4e6h9n X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 3FD28180008 X-HE-Tag: 1688956842-847617 X-HE-Meta: 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 OJ6iEDzc BgsJcWznvCOG1WWS5YsKwcYb7n1ZdF38UcG5eQmrwbQY9y7/Bwk0aLqseaxEGe1i2gPmi4QrzSc0E0eZ6A3Zk0EnD0y+GARpIG7B4iwKULZgQaJfshMM2tSojxKxjzNgpWfwNHL/eELXuVE/vg98MiKmvdGq633SWNIrZRDJ8onkKyki6tmmuRtOfkf5uXEX/iEHgLb2h/ixxEEsmQwKE14vpNUmBzKGChk5TZu5S8tUlCNchUl0vqdYK9JSz5hlDdQ1sFMBclFUOJ11LBfk7wX+OJq/HCtqdt5JvAMhW0+PfjZcocb0asyw/lEILgTrxLomOb5QYUUvMFmrG3DUCKmIqWnVCinB9w+w+Uft8ZdXgP05qeINjSC2UHM3E4Z/mgbJVKIx+toPcc6RZnWtAULBoiyaJM6Uf2dcYKeKCJU95+qx4LZUBTQp+3OHeglgLMLau X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun, 9 Jul 2023, David Rientjes wrote: > There are some substantial performance degradations, most notably > context_switch1_per_thread_ops which regressed ~21%. I'll need to repeat > that test to confirm it and can also try on cascadelake if it reproduces. > So the regression on skylake for will-it-scale appears to be real: LABEL | COUNT | MIN | MAX | MEAN | MEDIAN | STDDEV | DIRECTION ----------------------------------+-------+------------+------------+------------+------------+--------+------------ context_switch1_per_thread_ops | | | | | | | (A) v6.1.30 | 1 | 314507.000 | 314507.000 | 314507.000 | 314507.000 | 0 | (B) v6.1.30 slab_nomerge | 1 | 257403.000 | 257403.000 | 257403.000 | 257403.000 | 0 | !! REGRESSED !! | | -18.16% | -18.16% | -18.16% | -18.16% | --- | + is good but I can't reproduce this on cascadelake: LABEL | COUNT | MIN | MAX | MEAN | MEDIAN | STDDEV | DIRECTION ----------------------------------+-------+------------+------------+------------+------------+--------+------------ context_switch1_per_thread_ops | | | | | | | (A) v6.1.30 | 1 | 301128.000 | 301128.000 | 301128.000 | 301128.000 | 0 | (B) v6.1.30 slab_nomerge | 1 | 301282.000 | 301282.000 | 301282.000 | 301282.000 | 0 | | | +0.05% | +0.05% | +0.05% | +0.05% | --- | + is good So I'm a bit baffled at the moment. I'll try to dig deeper and see what slab caches this benchmark exercises that apparently no other benchmarks do. (I'm really hoping that the only way to recover this performance is by something like kmem_cache_create(SLAB_MERGE).)