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Fri, 07 Aug 2026 05:12:57 -0700 (PDT) Received: from google.com ([2a00:79e0:2031:6:f4e3:f7a5:b8dd:b3e9]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39085dea04bsm4903670a91.8.2026.08.07.05.12.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 07 Aug 2026 05:12:56 -0700 (PDT) Date: Fri, 7 Aug 2026 21:12:52 +0900 From: Sergey Senozhatsky To: Xueyuan Chen , Nhat Pham , Barry Song , Yosry Ahmed , Johannes Weiner , Brian Geffon Cc: Sergey Senozhatsky , Minchan Kim , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, xueyuan.chen21@gmail.com Subject: Re: [RFC PATCH 0/2] mm: zsmalloc: make shrinker compaction budget-aware Message-ID: References: <47ed45b5-de67-41aa-aa21-a3ba3479a7cc@vivo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <47ed45b5-de67-41aa-aa21-a3ba3479a7cc@vivo.com> X-Stat-Signature: 6jgfmjx53gfijch9om8sbtkmujyxuhd4 X-Rspamd-Queue-Id: 70507A0003 X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1786104778-66606 X-HE-Meta: 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 r61GQXVg Y2q9SFF0sKQA7qPPG6vSXDrVrXmHDAhlnMFtj30q8AQoVS/OWf+6sgaS34P+VoTmt+ld5p2xHOTJ80e/Vwf/Kinm2CGdYVPz4kQO4N84T0LNn64lfSRAHCtNuTZJoJvNNLCmGDP8t2hakQySYKL/sv49HNer6lvYZd+wu5fnceb3SUqSVv4lJOy9qZlaF/7k/A4RGnZDdA0+fiJYkhoUk0L8/3IBX/T4G10gX4KAsAvwwnqWjsTdOrp0IGYAdjTbwLP3GkWTWvBzl7KkafNrBaIktWDPGqeBdpOzygs+cDpS4AtgpIm4y4udj2J9SpbYGxriMpwlF/r95wMBnVUT8cUdNW+oK0iqOfWtZHrYQlbZz4A1dXVX1WxgOa+9037OxeAcyXKX8eF6D1b4Vr7BSuFV5xoDDVcweoL18VRlzVfiv+bksreSCL6AOscIGg8mX6qVneY0Xv3MEP6M= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On (26/08/07 18:57), Xueyuan Chen wrote: > Hi Sergey, > > Here is some additional data: > > I used the following definitions: >   compactable ratio = freeable_pages / total_pages >   memory reclaimed  = pages_freed * PAGE_SIZE > > freeable_pages is the estimate before compaction, based on the same > calculation as zs_shrinker_count(), while pages_freed is the actual > number of backing pages released. > > There were 264 callbacks in the trace: >   callback elapsed time: >     median:    5.77 ms >     p95:      55.82 ms >     maximum: 271.36 ms > >   compactable ratio before compaction: >     median:   0.32% >     p95:      2.86% >     maximum:  8.33% > >   memory reclaimed per callback: >     median:    3.80 MiB >     p95:      30.45 MiB >     maximum:  92.73 MiB > > The longest callback took 271.36 ms. Its compactable ratio was 3.25%, > and it released 7,650 pages, or about 29.88 MiB. > > There was also a 241.91 ms callback (with 30 schedule-outs) with a > compactable ratio of 0.44%. It released 1,019 pages, or about > 3.98 MiB. > > Based on this data, it seems better to remove the shrinker. > > Would you prefer that I change v2 to remove the zsmalloc shrinker > callbacks directly? Let's bring in heavy artillery to this discussion, in addition to Andrew and Minchan, adding Nhat, Yosry, Barry, Johannes, Brian (random order). Folks, I'm bullish on removal of zsmalloc shrinker callbacks. I don't think those buy us much apart from memcpy-s and lock contention. Systems that want to compact zsmalloc have a sysfs knob (and API) to do so (based on zram mm_stat numbers). Any thoughts?