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Tue, 09 Sep 2025 09:16:07 -0700 (PDT) MIME-Version: 1.0 References: <20250909065349.574894-1-liulei.rjpt@vivo.com> In-Reply-To: From: Chris Li Date: Tue, 9 Sep 2025 09:15:56 -0700 X-Gmail-Original-Message-ID: X-Gm-Features: AS18NWD8Bdipbsrc2Xnoz893tOcQg79yI5VZd6lbFZnJZu1va_aTGBEbLnomork Message-ID: Subject: Re: [PATCH v0 0/2] mm: swap: Gather swap entries and batch async release To: Barry Song <21cnbao@gmail.com> Cc: Kairui Song , Lei Liu , Michal Hocko , David Rientjes , Shakeel Butt , Andrew Morton , Kemeng Shi , Nhat Pham , Baoquan He , Johannes Weiner , Roman Gushchin , Muchun Song , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Brendan Jackman , Zi Yan , "Peter Zijlstra (Intel)" , Chen Yu , Hao Jia , "Kirill A. Shutemov" , Usama Arif , Oleg Nesterov , Christian Brauner , Mateusz Guzik , Steven Rostedt , Andrii Nakryiko , Al Viro , Fushuai Wang , "open list:MEMORY MANAGEMENT - OOM KILLER" , open list , "open list:CONTROL GROUP - MEMORY RESOURCE CONTROLLER (MEMCG)" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: F2C611C0018 X-Rspamd-Server: rspam05 X-Stat-Signature: 5834zd46j5khk9grr81fx3josxxhd34d X-Rspam-User: X-HE-Tag: 1757434570-81638 X-HE-Meta: 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 irYSRBh3 omshyXoMGG7Jj2ytsZUe4APsqiv2MC2C0/fMUOEQU8HMMwwAhw2ybpvvbHKsEQHp7q6DMoC705BWGwMLCmZ6Nlesk8MsURiouvp6DSTIVkQo9+b4eQztsOM9Fg0NApoxwrokzo0PzAO8piseuXzo5KL4g2cpA7X82W1Umfgq4HrXtulJDRfCG24siS1R9fhMH9mt2mQpMqaK2tBP5od7IuBYcpsNsLlaIle4+bTRHQqaWd8LtL8lj6IUrCoA4k+AnZHc/9VIKu+vkEr5X0bMpSGTRufkQSB2wSY+6QpauYmEAnxng8368lCa4jw== 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: List-Subscribe: List-Unsubscribe: On Tue, Sep 9, 2025 at 2:24=E2=80=AFAM Barry Song <21cnbao@gmail.com> wrote= : > I feel the cover letter does not clearly describe where the bottleneck > occurs or where the performance gains originate. To be honest, even > the versions submitted last year did not present the bottleneck clearly. > > For example, is this due to lock contention (in which case we would > need performance data to see how much CPU time is spent waiting for > locks), or simply because we can simultaneously zap present and > non-present PTEs? I have done some long tail analysis of the zswap page fault a while back, before zswap converting to xarray. For the zswap page fault, in the long tail a good chunk is a bath free swap slot. The breakdown inside shows a huge chunk is the clear_shadow() followed by memsw_uncharge(). I will post the link to the breakdown image once it is available. Chris