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AJvYcCV3pii6TOe1OKR9aKo3ieqmdPBr4rMNN89Vg2dA93cXIS+DiAI9RSfNSYh1aJb+7+bBRQgE/CKAa8vUor7feuQxTfQ= X-Gm-Message-State: AOJu0Yx29Vrh55503b9V9Hg/5bWeu1MENPhQwe6aV3/x/m1lnOTI4ZMD 6eFBJ45THon1CbuIzxJnwz2gwX/Il+QvaAUBHm6a3N7QhJjLX3uUBoZRjXdKh7Y7Ekcn6Al1YOn 0zRnn93oQcJJAM/swj0xx0wf4WW8= X-Google-Smtp-Source: AGHT+IG37BJLgtBHkGv7Y3iibJrinYDDdhWJQVnbqgcbL4cpy4bo4GDWF65hOrpSJjiNSYNUi6IVbr9PF4yhXjlIH70= X-Received: by 2002:a05:6102:f10:b0:48f:db40:99e9 with SMTP id ada2fe7eead31-49031dd824amr16516144137.0.1720826343044; Fri, 12 Jul 2024 16:19:03 -0700 (PDT) MIME-Version: 1.0 References: <20240706022523.1104080-1-flintglass@gmail.com> <20240706022523.1104080-4-flintglass@gmail.com> In-Reply-To: <20240706022523.1104080-4-flintglass@gmail.com> From: Nhat Pham Date: Fri, 12 Jul 2024 16:18:52 -0700 Message-ID: Subject: Re: [PATCH v2 3/6] mm: zswap: proactive shrinking before pool size limit is hit To: Takero Funaki Cc: Johannes Weiner , Yosry Ahmed , Chengming Zhou , Jonathan Corbet , Andrew Morton , Domenico Cerasuolo , linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 18C58C0014 X-Stat-Signature: y4myik36hzx6jee5g77safc9artkzhzf X-Rspam-User: X-HE-Tag: 1720826343-198610 X-HE-Meta: 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 OkbiZKeP UB+ouGhkZQnnA9DbnV44GkjDaGRCydvoheNzxwf6H7/EK8vxqjLoNgQ/MLUv7vbG9mwXBAc0wgP2D/Q04cvdPCNwoIRZ8gl0gJfi/Omh+1fYgNGB0EQGb8HzKeGBQiTR2z2qU3/FIKyTwxAQzWaKWTRE1ptyE30d8QdJIPzKeKgjv4sgDUq193IGz2HqdDwKPEmbu1rjYrRCysu3lOMD4B3s0PgO7s4/nIFbXwdevZ0FPFYiQn44/uDMI8WT12+HDiqk8K2Iahh7X7CLSPsVsDExscwKKg6O15kFdlWYM7eCgODxncSyLmgfaGy9jx0sLfs9v X-Bogosity: Ham, tests=bogofilter, spamicity=0.000457, 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 Fri, Jul 5, 2024 at 7:25=E2=80=AFPM Takero Funaki = wrote: > > This patch implements proactive shrinking of zswap pool before the max > pool size limit is reached. This also changes zswap to accept new pages > while the shrinker is running. > > To prevent zswap from rejecting new pages and incurring latency when > zswap is full, this patch queues the global shrinker by a pool usage > threshold between 100% and accept_thr_percent, instead of the max pool > size. The pool size will be controlled between 90% to 91% for the > default accept_thr_percent=3D90. Since the current global shrinker > continues to shrink until accept_thr_percent, we do not need to maintain > the hysteresis variable tracking the pool limit overage in > zswap_store(). > > Before this patch, zswap rejected pages while the shrinker is running > without incrementing zswap_pool_limit_hit counter. It could be a reason > why zswap writethrough new pages before writeback old pages. With this > patch, zswap accepts new pages while shrinking, and zswap increments > the counter when and only when zswap rejects pages by the max pool size. > > Now, reclaims smaller than the proactive shrinking amount finish > instantly and trigger background shrinking. Admins can check if new > pages are buffered by zswap by monitoring the pool_limit_hit counter. > > The name of sysfs tunable accept_thr_percent is unchanged as it is still > the stop condition of the shrinker. > The respective documentation is updated to describe the new behavior. > > Signed-off-by: Takero Funaki Code-wise and idea-wise, I like this patch :) This is dependent on other changes (as you have pointed out), but if the series goes through, please feel free to include: Reviewed-by: Nhat Pham