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Mon, 21 Sep 2026 08:49:01 -0700 (PDT) Date: Mon, 21 Sep 2026 11:48:57 -0400 From: Gregory Price To: Rik van Riel Cc: Kairui Song , Chris Li , Johannes Weiner , Baoquan He , Nhat Pham , Michal Hocko , Roman Gushchin , Shakeel Butt , Yosry Ahmed , David Hildenbrand , Muchun Song , Kemeng Shi , Barry Song , YoungJun Park , Chengming Zhou , "Lorenzo Stoakes (Oracle)" , "Liam R. Howlett" , "Vlastimil Babka (SUSE)" , Mike Rapoport , Suren =?utf-8?B?QmFnaGRhc2FyeWFu77+8?= , Qi Zheng , Axel Rasmussen , Yuanchu Xie , Wei Xu , Wenchao Hao , Jonathan Corbet , Hugh Dickins , Baolin Wang , Tejun Heo , Michal =?utf-8?Q?Koutn=C3=BD?= , Shuah Khan , Kunwu Chan , Meta kernel team , Linux Memory Management List , Linux Kernel Mailing List , linux-doc@vger.kernel.org, "open list:CONTROL GROUP - MEMORY RESOURCE CONTROLLER (MEMCG)" , Andrew Morton , Joshua Hahn Subject: Re: Path forward for Virtualized Swap? Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: A1BB4C000A X-Stat-Signature: 6sty7xe5z9dra964nqz74p77mt1zae5f X-Rspam-User: X-HE-Tag: 1790005742-384843 X-HE-Meta: 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 vc+kHAtt obA12ElMQPxw2wzBkmXLedCnWfo/cw50OoQCHl/zrnYorBbQ3SBiyr+cjPwLKc3xAbdj31/LTajrX35hawQAA0hJekGRcjd4rZOtGLXd7IO2MIJnbHDnAMp+ie/SH5X3W9YlccwmqkrWnuEUvOg919QSNvbF/AkEvLTDU5zzR6rWkxiwpUuDRAP1nlXD8V1xtCjWM6tbYEGAuovkmsJs4tjy1RdThei2GfXGb3uEANB/my8ZGWaJ68mDMvVqGf+FlB+wl6X1S5TQE2Uw0VgS3QhysWgrPhfyLQneiXVw3Wqaj6hbhwmjjevoiG7h/EXsq++xbheGfl5AvtQlP66pXWRbVw/qTlKuo5CXDtKQJQ4lHgOvknLYs3yhz6gJy/ki6ZiHee+AV3PzDKWQFhBNuJEtvpbLGwEsqsqzFNL4pNxPhlYgEl9FiQVosSelQEXMqqq8HDkPU4q9Yi0yNtavMvHWY4g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Sep 21, 2026 at 11:27:53AM -0400, Rik van Riel wrote: > On Mon, 2026-09-21 at 09:27 -0400, Gregory Price wrote: > > > > In short: > > > >   memory.swap   = logical swap       - workload/SLO limit > >   memory.pswap  = physical swap      - storage limit > >   memory.zswap  = compressed memory  - RAM limit > > > > This would preserve the existing memory.swap semantics while allowing > > both backing resources to be constrained independently. > > > My first thought was "this is confusing", but > after a minute I realized that most users will  > never set those options to anything other than  > "0" or "max", and the few who do only need to > touch one of them. > In practice, at most two (zswap + pswap) with swap=max. There's not much of a reason to set swap to anything other than max if you already have zswap and pswap limits. But for existing users where they're using it as an SLO signal, they could continue getting the existing behavior by just using swap.max. That said: I'm not convinced this is actually required, because the swap counter was never an SLO mechanism - it is a physical swap provisioning mechanism. If it's being used as an SLO mechanism, those users have misinterpreted its documented meaning. memory.min / memory.low already provide you this logical limit mechanism - so I would argue the parties that want such a split (rather than treating zswap / swap *as* the split) need to prove their use case cannot be supported by existing counters. ~Gregory