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Wed, 20 Dec 2023 16:50:32 -0800 (PST) MIME-Version: 1.0 References: <20231207192406.3809579-1-nphamcs@gmail.com> <20231218144431.GB19167@cmpxchg.org> <20231220051523.GB23822@cmpxchg.org> <20231220145025.GC23822@cmpxchg.org> In-Reply-To: From: Nhat Pham Date: Wed, 20 Dec 2023 16:50:20 -0800 Message-ID: Subject: Re: [PATCH v6] zswap: memcontrol: implement zswap writeback disabling To: Yosry Ahmed Cc: Johannes Weiner , akpm@linux-foundation.org, tj@kernel.org, lizefan.x@bytedance.com, cerasuolodomenico@gmail.com, sjenning@redhat.com, ddstreet@ieee.org, vitaly.wool@konsulko.com, mhocko@kernel.org, roman.gushchin@linux.dev, shakeelb@google.com, muchun.song@linux.dev, hughd@google.com, corbet@lwn.net, konrad.wilk@oracle.com, senozhatsky@chromium.org, rppt@kernel.org, linux-mm@kvack.org, kernel-team@meta.com, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, david@ixit.cz, chrisl@kernel.org, Wei Xu , Yu Zhao Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 4F71880010 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: ytq4wf68oyg39ey3g1xtiddx6yscnrti X-HE-Tag: 1703119833-261269 X-HE-Meta: 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 GS84tArG 1pdE7NDcHTKn1PIXstZUFnQqIr4rRJ/Ex9DhEALyPtzg/SAcnNb7R6B9lLW/Wd8TsXpq3Fampm0CYpDFRDcwJeX+9LrOd7aPKyrWJS76l8PsrlprhL/w/mODxw4A/ATzYAxurSb1ez9tEs3sZgutKrfWN/vnfuz3o7NpXDbaMBQ6FC7/0U25m8PAfb+3AxlATvcM60eyfS5NOhyr1IImgV4yEJ7W/S9/7CLaKzvfSWLSQFcpbUkCwe7ikon8s0n4kEGcbDzKZoufrQeEH1za56rNSMe3DLPMvLWH2vPlhiYmHF706AQPxvVh2P8gZP2ecEwn56fEAtCexk1r9zuTuhf8L6pXtreHZ6mz4SvXVIgTrAJHsGEaf5WO9YA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.002997, 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 Wed, Dec 20, 2023 at 4:24=E2=80=AFPM Yosry Ahmed = wrote: > > We can agree to disagree here, I am not trying to block this anyway. > But let's at least document this in the commit message/docs/code > (wherever it makes sense) -- that recurrent failures (e.g. > incompressible memory) may keep going back to zswap only to get > rejected, so workloads prone to this may observe some reclaim > inefficiency. I'll add the following caveat: Note that if the store failures are recurring (for e.g if the pages are incompressible), users can observe reclaim inefficiency after disabling writeback (because the same pages might be rejected again and again). to the zswap documentation and the cgroup documentation then? I'll repeat this caveat in both places for self-containment purposes.