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Tue, 14 Nov 2023 09:20:22 -0800 (PST) MIME-Version: 1.0 References: <20231106231158.380730-1-nphamcs@gmail.com> In-Reply-To: <20231106231158.380730-1-nphamcs@gmail.com> From: Yosry Ahmed Date: Tue, 14 Nov 2023 09:19:47 -0800 Message-ID: Subject: Re: [PATCH v4] zswap: memcontrol: implement zswap writeback disabling To: Nhat Pham Cc: akpm@linux-foundation.org, tj@kernel.org, lizefan.x@bytedance.com, hannes@cmpxchg.org, 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 5C32D4000C X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 43tdqf3kcdr9wr58r63ase4badr7y39t X-HE-Tag: 1699982424-38145 X-HE-Meta: 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 soRBIyFm KQQrCm734utzL9xBAOon3ZmoSYpB2E5dP1B+Ughil9Nt+u2Q1rOuMGwzitoPN4FUDeUyeLWSEEW7yd4E20g0tSnhqIdNXkydtODhQZpKejtSwPWqtjdzz7FCI/DIl9+11OwOc7SvQzGU6FSESHIl4EWBVhF8QiMj8yFK4EVi3EPhArwc2FNXd9VvZFZgfFFpUpw06PpjNXYwIo9dQg8aeFNjcOrHUoG8JVGQY9n9cxdNchcxsXMz85uSP7uWflq1VbkAqb9XfdJNh1FtHczO8AQjNQZkuCYdvH8a8tpAEzJljeCr2IN0rMiTciU5S7n0tphX4axtrLoczNuk= 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 Mon, Nov 6, 2023 at 3:12=E2=80=AFPM Nhat Pham wrote: > > During our experiment with zswap, we sometimes observe swap IOs due to > occasional zswap store failures and writebacks-to-swap. These swapping > IOs prevent many users who cannot tolerate swapping from adopting zswap > to save memory and improve performance where possible. > > This patch adds the option to disable this behavior entirely: do not > writeback to backing swapping device when a zswap store attempt fail, > and do not write pages in the zswap pool back to the backing swap > device (both when the pool is full, and when the new zswap shrinker is > called). > > This new behavior can be opted-in/out on a per-cgroup basis via a new > cgroup file. By default, writebacks to swap device is enabled, which is > the previous behavior. Initially, writeback is enabled for the root > cgroup, and a newly created cgroup will inherit the current setting of > its parent. > > Note that this is subtly different from setting memory.swap.max to 0, as > it still allows for pages to be stored in the zswap pool (which itself > consumes swap space in its current form). > > Suggested-by: Johannes Weiner > Signed-off-by: Nhat Pham LGTM, Reviewed-by: Yosry Ahmed