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Fri, 27 Jan 2023 03:45:34 -0800 (PST) Date: Fri, 27 Jan 2023 20:45:28 +0900 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> To: Roman Gushchin Cc: Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Ingo Molnar , Johannes Weiner , Michal Hocko , Shakeel Butt , Muchun Song , Matthew Wilcox , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH mm-unstable] lib/Kconfig.debug: do not enable DEBUG_PREEMPT by default Message-ID: References: <20230121033942.350387-1-42.hyeyoo@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: DC79510000D X-Stat-Signature: 199x5d4yeyb9n1ufed3mppbrnnzju1z5 X-HE-Tag: 1674819936-109259 X-HE-Meta: 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 DuGGk77o 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 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 Wed, Jan 25, 2023 at 06:02:04PM -0800, Roman Gushchin wrote: > On Sat, Jan 21, 2023 at 12:39:42PM +0900, Hyeonggon Yoo wrote: > > In workloads where this_cpu operations are frequently performed, > > enabling DEBUG_PREEMPT may result in significant increase in > > runtime overhead due to frequent invocation of > > __this_cpu_preempt_check() function. > > > > This can be demonstrated through benchmarks such as hackbench where this > > configuration results in a 10% reduction in performance, primarily due to > > the added overhead within memcg charging path. > > > > Therefore, do not to enable DEBUG_PREEMPT by default and make users aware > > of its potential impact on performance in some workloads. > > > > hackbench-process-sockets > > debug_preempt no_debug_preempt > > Amean 1 0.4743 ( 0.00%) 0.4295 * 9.45%* > > Amean 4 1.4191 ( 0.00%) 1.2650 * 10.86%* > > Amean 7 2.2677 ( 0.00%) 2.0094 * 11.39%* > > Amean 12 3.6821 ( 0.00%) 3.2115 * 12.78%* > > Amean 21 6.6752 ( 0.00%) 5.7956 * 13.18%* > > Amean 30 9.6646 ( 0.00%) 8.5197 * 11.85%* > > Amean 48 15.3363 ( 0.00%) 13.5559 * 11.61%* > > Amean 79 24.8603 ( 0.00%) 22.0597 * 11.27%* > > Amean 96 30.1240 ( 0.00%) 26.8073 * 11.01%* > > > > Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> > > Nice! > > I checkout my very simple kmem performance test (1M allocations 8-bytes allocations) > and it shows ~30% difference: 112319 us with vs 80836 us without. Hello Roman, Oh, it has higher impact on micro benchmark. > > Probably not that big for real workloads, but still nice to have. > > Acked-by: Roman Gushchin Thank you for kindly measuring impact of this patch and giving ack! > Thank you! > -- Thanks, Hyeonggon