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Tue, 28 Feb 2023 18:27:38 -0800 (PST) Received: from [10.200.10.215] ([139.177.225.225]) by smtp.gmail.com with ESMTPSA id i194-20020a636dcb000000b004f1e73b073bsm6246368pgc.26.2023.02.28.18.27.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 28 Feb 2023 18:27:38 -0800 (PST) Message-ID: <04953598-accc-7eac-1960-94a4fed580fd@bytedance.com> Date: Wed, 1 Mar 2023 10:27:27 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Subject: Re: [PATCH v3 0/8] make slab shrink lockless To: Michal Hocko , Mike Rapoport Cc: Andrew Morton , tkhai@ya.ru, hannes@cmpxchg.org, shakeelb@google.com, roman.gushchin@linux.dev, muchun.song@linux.dev, david@redhat.com, shy828301@gmail.com, sultan@kerneltoast.com, dave@stgolabs.net, penguin-kernel@i-love.sakura.ne.jp, paulmck@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20230226144655.79778-1-zhengqi.arch@bytedance.com> <20230226115100.7e12bda7931dd65dbabcebe3@linux-foundation.org> Content-Language: en-US From: Qi Zheng In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 3DDAF140011 X-Rspam-User: X-Stat-Signature: 85dxu8neqa9nrwfzz7tyufoqz7jqsmh6 X-HE-Tag: 1677637660-833048 X-HE-Meta: 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 gGrX42S3 k0a7TMolY6K2K5wUhIb/LiFysk9o5Q519ThNvg9w+Yk5/B/Tj/AjUNgZCYJoqRJeBj1SfS/4Nv8sYOsSkNHdy529aGSoVs7ui+6Lwwgp8+Es6enLb1uCUWY1Oe5cJWfGvajrEqKTO5C6otp0yGFEn36M0zCq0csysZq8BFnQOSw5fkF8Uk1EFoMLR/sE1zq2gWkrknWW2luftSdM7/ftxiY53AuXKQcx8HHQoK7nl1rsBALAAjbfZi5bHdTujZWfDmvvFSUcz/Nn6gbVkXTcFCVKmYs2BoVRr95Re77+suMEgBRjnS98G9T2UMctvEjxVl3p0T2ZBr4XFKmjsFVoENXoEHRGqVphyAhqrkZA0ttI1b0zdXMiYE4/JKA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000020, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2023/3/1 02:40, Michal Hocko wrote: > On Mon 27-02-23 17:08:30, Mike Rapoport wrote: > [...] >> The results you present do show improvement in IPC for an artificial test >> script. But more interesting would be to see how a real world workloads >> benefit from your changes. > > It's been quite some time ago (2018ish) when we have seen bug report > where mount got stalled when racing with memory reclaim. This was > nasty because the said mount was a part of login chain and users simply > had to wait for a long time to get loged in in that particular > deployment. > > The mount was blocked on a shrinker registration and the reclaim was > stalled in a slab shrinker IIRC. I do not remember all the details but > the underlying problem was that a shrinker callback took a long time > because there were too many objects to scan or it had to sync with other > fs operation. I believe we ended up using Minchan's break out from slab > shrinking if the shrinker semaphore was contended and that helped to > some degree but there were still some corner cases where a single slab > shrinker could take a noticeable amount of time. > > In general using a "big" lock like shrinker_rwsem from the reclaim and > potentially block many unrelated subsystems that just want to register > or unregister shrinkers is a potential source of hard to predict > problems. So this is a very welcome change. Totally agree. :) Thanks, Qi