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AJvYcCWILvWeFJ4tWEaVRKXgZMXfV1wWqct8BO+YR67NgxaVdv69f7PruIstvd0/9lFxjRYuILBwjzWCiQ==@kvack.org X-Gm-Message-State: AOJu0Yw/gy2ONYHRDGjFzjFsn2Nza8WyX2sQzGleuBZXK8QGlkA7LTXQ mxYXMynJqIC4WY60x+Nf2vOVTIYrk+aUG+ewOhEsz5MscD0NkCYnbI3H/1kI2P6BEdewzN1UkE7 lIbgKjrZsrSIk8ELAqcPprhKNfuJ/gG4= X-Gm-Gg: ASbGncsoCWldL3+T2++heUKvK8U/cfzXVFDpRaBxXzr46vnWGFCgrfM15a7qH2UM46Q fbwdKFsym5jLso5MWi0VRU/Iu3VctWcDcR7JX3TVTBP0aBSD9d1XY/C3t49LVWVWXMYZOIaCDAy Qkar0CEXYohkSiWztyDFiILVKEG3uWwIM92WzNYWQtgnLA0VzhYGIEoMhfKfo8s7ZtpTyRkMQ0P u1mSXA= X-Google-Smtp-Source: AGHT+IFKWuYJwFL/TSEMQ2ahjFJ9+k6YIyKX3uyxdbHn8KcO8+Zy6yyb03qRPbsqbjWe3FwKP26ZJ/nzd0auZK37yTY= X-Received: by 2002:a05:6e02:3f0d:b0:3e3:fdd9:8972 with SMTP id e9e14a558f8ab-3e41615d9c0mr242900825ab.11.1754413001753; Tue, 05 Aug 2025 09:56:41 -0700 (PDT) MIME-Version: 1.0 References: <20250805002954.1496-1-sj@kernel.org> <761a2899-6fd9-4bfe-aeaf-23bce0baa0f1@redhat.com> In-Reply-To: <761a2899-6fd9-4bfe-aeaf-23bce0baa0f1@redhat.com> From: Nhat Pham Date: Tue, 5 Aug 2025 09:56:29 -0700 X-Gm-Features: Ac12FXwKyCyXaDbbCA1d5wEx5xyJYQALLRbD4ssEiJbWg--hw6b-8mhARiZxjN4 Message-ID: Subject: Re: [RFC PATCH v2] mm/zswap: store Cc: SeongJae Park , "Liam R. Howlett" , Andrew Morton , Chengming Zhou , Johannes Weiner , Jonathan Corbet , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Suren Baghdasaryan , Vlastimil Babka , Yosry Ahmed , kernel-team@meta.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Takero Funaki Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: D8DE01C0005 X-Stat-Signature: tmxac6gnr7cafc1c9egz6aziczadaemy X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1754413002-823236 X-HE-Meta: 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 iEFXTprE bPGgTbt96uYQ+AtZ5Qp9gfISGKq7LICJpsqtAyORka/Z/C81L1/nxJkNV5I4O0V2fwjNvzBcc5nevZc4bGz6U/XOH9w5/s1TH2tpyGfccOJDR07sj2UjPqB3WI1P3UXTSKdzdb7PGPV80zvGUsEXSe2G3eLSz7SdxC1T/EoP1gSfP/WZ88dVwP5N31BsZrUvalszp/C2pyq6qZpcUx7J8E++WnupcsW1Rg1TEORhZ3Q3jcg+cZQwlEoe/OXPb0ttdCGb1zttOmGrEC0QsX27PtySF4iHjCBQJmkBKl2emsKBsc3vuSjpyNQFuLNYpBYlOE7iXMV+RgPCgOCChVSrjo5ZfUmXpMpRrJS7UoiuCEw5QqDuGqOcff0qlgiFWFt2jvbHs09KpZWNZK3KYTMuhr9mxxEQJ7qftjKs6VHS3JI7aGyQcI4oLw8QheNh9A0qtTapSZ8dYfRQuD91njvRXYjzW1f3EGY9beEG3 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, Aug 5, 2025 at 3:47=E2=80=AFAM David Hildenbrand = wrote: > > On 05.08.25 02:29, SeongJae Park wrote: > > When zswap writeback is enabled and it fails compressing a given page, > > the page is swapped out to the backing swap device. This behavior > > breaks the zswap's writeback LRU order, and hence users can experience > > unexpected latency spikes. If the page is compressed without failure, > > but results in a size of PAGE_SIZE, the LRU order is kept, but the > > decompression overhead for loading the page back on the later access is > > unnecessary. > > > > Keep the LRU order and optimize unnecessary decompression overheads in > > the cases, by storing the original content in zpool as-is. > > Does this have any effect on the movability of the given page? IOW, does > page migration etc. still work when we store an ordinary page of an > shmem/anon folio here? Good question. This depends on the backend allocator of zswap, but the only backend allocator remaining (zsmalloc) does implement page migration. It's why we insisted on using zpool/zsmalloc to handle the incompressibility case as well: https://lore.kernel.org/all/CAKEwX=3DNC65XCkmX1YzivEJtPc+sEJ3pLHUsYhF60QJnk= _OtpVw@mail.gmail.com/ > > -- > Cheers, > > David / dhildenb >