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From: "Jiayuan Chen" Message-ID: TLS-Required: No Subject: Re: [PATCH v1] mm: zswap: add per-memcg stat for incompressible pages To: "Nhat Pham" Cc: linux-mm@kvack.org, "Jiayuan Chen" , "Johannes Weiner" , "Michal Hocko" , "Roman Gushchin" , "Shakeel Butt" , "Muchun Song" , "Yosry Ahmed" , "Chengming Zhou" , "Andrew Morton" , "Nick Terrell" , "David Sterba" , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, "Chris Li" In-Reply-To: References: <20260205053013.25134-1-jiayuan.chen@linux.dev> X-Migadu-Flow: FLOW_OUT X-Stat-Signature: 33hjweq3hx6cxrrjqy548r51ew8pwo5n X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 8A0B1140003 X-HE-Tag: 1770343466-192918 X-HE-Meta: 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 eRyrPuM7 1ktLk8eqaO8KgX87S0jlFK3xdCA7vuYBucg1g6oISOirj5t2cRwd5Mfc1V0g37QFvQfiwnDHLzOHgkCokzJYE2YyxG1ZtofYbSFxIh30jqnFTmgTf3jcesle34D0n9pkl9UhRKoNN1M+Nr091vEqqXE+GGpLJMEsITmANbIqz5ZQ5LlT+WtAFIjv+V82n+wmFQfAKREnLPdHdIth0LxYAMp6tnhBqziWc20t7oW51c+b1LOlCaoLRAA7HpCCSvReDJEODKHDeKwIKVzlFkFWuNqIxYXRul8r2mQurw3j0w1UDlUM= 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: February 6, 2026 at 01:45, "Nhat Pham" wrote: >=20 >=20On Thu, Feb 5, 2026 at 9:31 AM Nhat Pham wrote: >=20 >=20>=20 >=20> On Wed, Feb 4, 2026 at 9:31 PM Jiayuan Chen wrote: > >=20 >=20> From: Jiayuan Chen > >=20 >=20> The global zswap_stored_incompressible_pages counter was added in = commit > > dca4437a5861 ("mm/zswap: store > to track how many pages are stored in raw (uncompressed) form in zsw= ap. > > However, in containerized environments, knowing which cgroup is > > contributing incompressible pages is essential for effective resourc= e > > management. > >=20 >=20> Add a new memcg stat 'zswpraw' to track incompressible pages per c= group. > > This helps administrators and orchestrators to: > >=20 >=20> 1. Identify workloads that produce incompressible data (e.g., encr= ypted > > data, already-compressed media, random data) and may not benefit fro= m > > zswap. > >=20 >=20> 2. Make informed decisions about workload placement - moving > > incompressible workloads to nodes with larger swap backing devices > > rather than relying on zswap. > >=20 >=20> 3. Debug zswap efficiency issues at the cgroup level without needi= ng to > > correlate global stats with individual cgroups. > >=20 >=20> While the compression ratio can be estimated from existing stats > > (zswap / zswapped * PAGE_SIZE), this doesn't distinguish between > > "uniformly poor compression" and "a few completely incompressible pa= ges > > mixed with highly compressible ones". The zswpraw stat provides dire= ct > > visibility into the latter case. > >=20 >=20Actually I forgot - can you also update the Documentation: >=20 >=20Documentation/admin-guide/cgroup-v2.rst >=20 >=20to include a short description of the new counter? Thanks! > Thanks Nhat for the review and Acked-by! I'll update the documentation and add Chris Li's link to changelog in v2. Will consider the selftest as a follow-up.