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Thu, 02 Jul 2026 05:32:51 -0700 (PDT) Message-ID: <5ce4035b-7f56-d1d2-2d2a-668446d870e8@gmail.com> Date: Thu, 2 Jul 2026 20:32:38 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.15.0 Subject: Re: [PATCH v5 4/6] mm/zswap: Implement proactive writeback From: Hao Jia To: Yosry Ahmed Cc: akpm@linux-foundation.org, tj@kernel.org, hannes@cmpxchg.org, shakeel.butt@linux.dev, mhocko@kernel.org, mkoutny@suse.com, nphamcs@gmail.com, chengming.zhou@linux.dev, muchun.song@linux.dev, roman.gushchin@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Hao Jia References: <20260629112032.20423-1-jiahao.kernel@gmail.com> <20260629112032.20423-5-jiahao.kernel@gmail.com> <4ec2bd64-af40-8ebf-b8a8-2dd7421a1100@gmail.com> In-Reply-To: <4ec2bd64-af40-8ebf-b8a8-2dd7421a1100@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2026/7/1 19:45, Hao Jia wrote: > > > On 2026/7/1 00:10, Yosry Ahmed wrote: >>>> Before going through more versions we need to figure out if this will >>>> pivot to be a proactive demotion interfcae for swap tiering. >>>> >>> >>> Yes. Should I drop patches 4-6 in the next version and wait for swap >>> tiering to be finalized? >>> We can try to get the non-memcg parts (patches 1-3) merged upstream >>> first. This would also give them plenty of time to bake and catch any >>> potential regressions. Thoughts? >> >> Patches 1-2 can be sent and merged separately, yes. For patch 2, >> please include some numbers for the writeback performance before and >> after batching. > > I'd love to collect some performance data. Do you have any recommended > benchmarks for this? > Perhaps the following test case could work? Test Setup: - Total memory: 32 GB - zswap settings: max_pool_percent=1, accept_threshold_percent=50, shrinker_enabled=N - cgroup constraint: memory.max=1G - Workload: Run the following stress-ng command inside the cgroup for 120s to continuously force zswap store failures and trigger shrink_worker(): bash -c 'echo $$ > /sys/fs/cgroup/zswaptest/cgroup.procs ; \ exec stress-ng --vm 4 --vm-bytes 4G --vm-keep --vm-method rand-set -t 120s -q' The following comparison results were collected over multiple runs via bpftrace and the 'written_back_pages' sysfs interface: Baseline Patched --------------------------------------------------- shrink_worker wakeups 5,587 878 shrink_memcg calls 7,823,853 2,347,320 written_back 257 781,214 Conclusion: Under the same workload and duration, the patched kernel shows a significant reduction in both shrink_worker wakeups and shrink_memcg calls, while successfully executing a much higher volume of page writebacks. Thanks， Hao