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a=rsa-sha256; c=relaxed/relaxed; d=stgolabs.net; s=dreamhost; t=1675309027; bh=T4S2v7ISuVZquux7kOo2tBD0hwS4H3XCBw+AEhFxwYw=; h=Date:From:To:Cc:Subject:Content-Type; b=CoaG4YtuB2SuPmf0ifRffFmn3ZJn2EAuxuAPZmpNQ/omMd2Kz9EEDe3cvWthCB9V8 kfGX8Z78C3B1jZenRh3/ZRep+QXmQU7ZymGkwLTozcNrhc1g5tub6K/KJD72fqcjU1 2MidsB2jYKFLmrwL0iMglMIzT4PVhll/TfNMHKWfd8pfxNYhO2jg3FjbVNnfPdt4Xg 6fwoj+SkdVlFCgfMZ3UKPkd10WEs+Oe0wybeWshBeZmldxG9mkjddKV13kugTKR8rp jvMWDKRozZpJl3T59EEP83nCd4ZRzUjkN4GebUeaku8H39EuCSb8Ho0FtvT02NuprJ 5De/zc0PyJ2cw== Date: Wed, 1 Feb 2023 19:09:55 -0800 From: Davidlohr Bueso To: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , 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: <20230202030955.nfejzcgn6edp6cgl@offworld> Mail-Followup-To: Hyeonggon Yoo <42.hyeyoo@gmail.com>, Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Ingo Molnar , Johannes Weiner , Michal Hocko , Shakeel Butt , Muchun Song , Matthew Wilcox , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20230121033942.350387-1-42.hyeyoo@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20230121033942.350387-1-42.hyeyoo@gmail.com> User-Agent: NeoMutt/20220429 X-Rspamd-Queue-Id: 6D420180005 X-Stat-Signature: 5sr68znxde1afkakiog1qiohib8wjrsb X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1675309029-764804 X-HE-Meta: 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 hKCzZWxA pIXC+62jT8xWRf4ttiRUdRAdiFiEem2TtR2pMTzjkqmY94O+5qiMg4L5EXQRypG9gfjXUmJHAdMkKjtRsE/x5De5LMxnbbnMGJyEAl9PO3m8TBmMNAHhOVU+BjKpDO9TI92982J0Svh2zSK6NbE69tQ6CPeVBKFQNlnVvXtnWbSWVFljgzS5ZFAtnxfeJb0IH1yiGO3AToM4P+7TSReBKZANSNWqvcY3hadmY0fKjCtBpzjqOl0VGd7p6Ze6U49t/N88HraapA3FF4x5vjRXMwluUoFYuxIAQMdn8IxI7vawC3O4V7T1uhZLQoTO/M/JtgoSte8vV0zlFkCUS3po3B+fK/8i8Unc1sVaXY0X98DMosrop6+qzdRFXC+ORS1EiXXKdV0guySw2GXsOXLL51OFbeFqdCaoypMmZxxQU2Ye1HoLiMDabj4W3iFtx8JN24emq2NRtMJGTGI4pmxuoKDhIs4IBN0Mt5Xh2BL8pnFjAKj7w4UFLQqOnaFp0d8hxq20r 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 Sat, 21 Jan 2023, 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> Acked-by: Davidlohr Bueso