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Thu, 01 Feb 2024 12:56:31 -0800 (PST) MIME-Version: 1.0 References: <20240201-b4-zswap-invalidate-entry-v1-0-56ed496b6e55@bytedance.com> <20240201-b4-zswap-invalidate-entry-v1-2-56ed496b6e55@bytedance.com> In-Reply-To: <20240201-b4-zswap-invalidate-entry-v1-2-56ed496b6e55@bytedance.com> From: Nhat Pham Date: Thu, 1 Feb 2024 12:56:20 -0800 Message-ID: Subject: Re: [PATCH 2/6] mm/zswap: invalidate zswap entry when swap entry free To: Chengming Zhou Cc: Johannes Weiner , Andrew Morton , Yosry Ahmed , linux-kernel@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 751EB16000C X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: yusfum3x3eb5wqju8g6ifxpidf8wyohh X-HE-Tag: 1706820992-131156 X-HE-Meta: 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 95VZOLKQ E/bwT+kf1yFPSArEdKsp+QlgBr7NLD207xvVV+z/DT53y1KhGaQgzCXuP8ZwNpKInA7RwWY7ibzOI5q0tvk8l5/3KFqL76L4S0SXl/RbjXqy+tKSJFcRONrZT7kzfueUDH1hAL8v9tIBuIDpzpm7W4HXwiZ5SyaFfoSVFlw/hhc6joTtfJYM6DBtccCD8zQhbJ0rtenXy1+/hQ7UpwY5+bA7j4s0LsMDzyLKdPLnC88/p0XUKydqwgJK4NcejGaW94UUQaHNRbQpYd/m5NylSry+IVQg3TkunM3DCJF1Melg2wyr/vNWdLjyj4S0qwLQHUzC3joD+sZTsV/PJTUpXj28yZ3dHK4rqsu0cGdz8UQ4Z23LvhtqH0bt/Dz54K9YDoQS875Io7RD4bBr5P7hXkr/qobpvPHHg+ysUgOl06lJesOPJj3b7yfzbBg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.001155, 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 Thu, Feb 1, 2024 at 7:50=E2=80=AFAM Chengming Zhou wrote: > > During testing I found there are some times the zswap_writeback_entry() > return -ENOMEM, which is not we expected: > > bpftrace -e 'kr:zswap_writeback_entry {@[(int32)retval]=3Dcount()}' > @[-12]: 1563 > @[0]: 277221 > > The reason is that __read_swap_cache_async() return NULL because > swapcache_prepare() failed. The reason is that we won't invalidate > zswap entry when swap entry freed to the per-cpu pool, these zswap > entries are still on the zswap tree and lru list. > > This patch moves the invalidation ahead to when swap entry freed > to the per-cpu pool, since there is no any benefit to leave trashy > zswap entry on the tree and lru list. > > With this patch: > bpftrace -e 'kr:zswap_writeback_entry {@[(int32)retval]=3Dcount()}' > @[0]: 259744 Nice! Reviewed-by: Nhat Pham