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Wed, 07 Jun 2023 02:16:46 -0700 (PDT) MIME-Version: 1.0 References: <20230606145611.704392-1-cerasuolodomenico@gmail.com> In-Reply-To: <20230606145611.704392-1-cerasuolodomenico@gmail.com> From: Yosry Ahmed Date: Wed, 7 Jun 2023 02:16:10 -0700 Message-ID: Subject: Re: [RFC PATCH v2 0/7] mm: zswap: move writeback LRU from zpool to zswap To: Domenico Cerasuolo Cc: vitaly.wool@konsulko.com, minchan@kernel.org, senozhatsky@chromium.org, linux-mm@kvack.org, ddstreet@ieee.org, sjenning@redhat.com, nphamcs@gmail.com, hannes@cmpxchg.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 803AFA0010 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: y1ke8da1fx7wxcnbzdw3xmukzz4th9jx X-HE-Tag: 1686129750-526533 X-HE-Meta: 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 /WANqIc7 xVSc+ism8oxgkGxmt8zlQ0yvDmHs1P0OdAx7Xo7ILh5Ym9ISFKgSdpdj7eFaZb94w6cGv85ltMitiZvChsI/YYGqPWpeW4Ic3CAgyCfZMgnIHqpVQfYe1W3slccbiXZ+smbPwmKzFdhacJ+DIFqmiUN2BC1JuLG8ihO/7Z+p7tlX/Py8gkV7MP6Imb6ddpMx3D3NVvutsq/oDwbDq0EBk2gkumMR/lbNb2AcP9nMyDI068e8T4O/D4Br/jmvB18+5UFfk5KmXsN3YSErAs+yO0JjC9A== 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: On Tue, Jun 6, 2023 at 7:56=E2=80=AFAM Domenico Cerasuolo wrote: > > This series aims to improve the zswap reclaim mechanism by reorganizing > the LRU management. In the current implementation, the LRU is maintained > within each zpool driver, resulting in duplicated code across the three > drivers. The proposed change consists in moving the LRU management from > the individual implementations up to the zswap layer. > > The primary objective of this refactoring effort is to simplify the > codebase. By unifying the reclaim loop and consolidating LRU handling > within zswap, we can eliminate redundant code and improve > maintainability. Additionally, this change enables the reclamation of > stored pages in their actual LRU order. Presently, the zpool drivers > link backing pages in an LRU, causing compressed pages with different > LRU positions to be written back simultaneously. > > The series consists of several patches. The first patch implements the > LRU and the reclaim loop in zswap, but it is not used yet because all > three driver implementations are marked as zpool_evictable. > The following three commits modify each zpool driver to be not > zpool_evictable, allowing the use of the reclaim loop in zswap. > As the drivers removed their shrink functions, the zpool interface is > then trimmed by removing zpool_evictable, zpool_ops, and zpool_shrink. > Finally, the code in zswap is further cleaned up by simplifying the > writeback function and removing the now unnecessary zswap_header. > > Based on mm-stable + commit 399ab221f3ff > ("mm: zswap: shrink until can accept") currently in mm-unstable. I tested this + commit fe1d1f7d0fb5 ("mm: zswap: support exclusive loads") currently in mm-unstable, using zsmalloc and CONFIG_ZSWAP_EXCLUSIVE_LOADS=3Dy. I only ran basic zswap tests with manual writeback induction and made sure everything is sane. I obviously hope you did more involved testing :) The only problem I came across is the conflict with fe1d1f7d0fb5, and I suggested the fix in patch 1. With the fix, everything seems correct. So I guess, FWIW for all the patches except 2 & 3 (for zbud and z3fold): Tested-by: Yosry Ahmed > > V2: > - fixed lru list init/del/del_init (Johannes) > - renamed pool.lock to lru_lock and added lock ordering comment (Yosry) > - trimmed zsmalloc even more (Johannes | Nhat) > - moved ref drop out of writeback function (Johannes) > > Domenico Cerasuolo (7): > mm: zswap: add pool shrinking mechanism > mm: zswap: remove page reclaim logic from zbud > mm: zswap: remove page reclaim logic from z3fold > mm: zswap: remove page reclaim logic from zsmalloc > mm: zswap: remove shrink from zpool interface > mm: zswap: simplify writeback function > mm: zswap: remove zswap_header > > include/linux/zpool.h | 19 +- > mm/z3fold.c | 249 +------------------------- > mm/zbud.c | 167 +----------------- > mm/zpool.c | 48 +---- > mm/zsmalloc.c | 396 ++---------------------------------------- > mm/zswap.c | 186 +++++++++++--------- > 6 files changed, 130 insertions(+), 935 deletions(-) > > -- > 2.34.1 >