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[195.250.132.146]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48e6db0b08asm83235955e9.8.2026.05.11.04.39.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 May 2026 04:39:50 -0700 (PDT) Date: Mon, 11 May 2026 13:39:48 +0200 From: Michal =?utf-8?Q?Koutn=C3=BD?= To: Hao Jia Cc: akpm@linux-foundation.org, tj@kernel.org, hannes@cmpxchg.org, shakeel.butt@linux.dev, mhocko@kernel.org, yosry@kernel.org, nphamcs@gmail.com, chengming.zhou@linux.dev, muchun.song@linux.dev, roman.gushchin@linux.dev, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Hao Jia Subject: Re: [PATCH 0/3] mm/zswap: Implement per-cgroup proactive writeback Message-ID: References: <20260511105149.75584-1-jiahao.kernel@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="o3jizhh4qfyisfpc" Content-Disposition: inline In-Reply-To: <20260511105149.75584-1-jiahao.kernel@gmail.com> --o3jizhh4qfyisfpc Content-Type: text/plain; protected-headers=v1; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH 0/3] mm/zswap: Implement per-cgroup proactive writeback MIME-Version: 1.0 On Mon, May 11, 2026 at 06:51:46PM +0800, Hao Jia = wrote: > From: Hao Jia >=20 > Zswap currently writes back pages to backing swap devices reactively, > triggered either by memory pressure via the shrinker or by the pool > reaching its size limit. However, this reactive approach makes writeback > timing indeterminate and can disrupt latency-sensitive workloads when > eviction happens to coincide with a critical execution window. >=20 > Furthermore, in certain scenarios, it is desirable to trigger writeback > in advance to free up memory. For example, users may want to prepare for > an upcoming memory-intensive workload by flushing cold memory to the > backing storage when the system is relatively idle. I can imagine the zswap writeout can come at the least possible moment... > To address these issues, this patch series introduces a per-cgroup > interface that allows users to proactively write back cold compressed > pages from zswap to the backing swap device. =2E..but I see this series is not only per-cgroup proactive reclaim but it's also age-based reclaim. The per-cg consumption and limits (and regular memory reclaim) are all measured in sizes. This age-based invocations don't seem commensurable (e.g. how would users in practice determine what is the desired input to here). Could you explain more reasoning behind this design? Thanks, Michal --o3jizhh4qfyisfpc Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iJEEABYKADkWIQRCE24Fn/AcRjnLivR+PQLnlNv4CAUCagHAARsUgAAAAAAEAA5t YW51MiwyLjUrMS4xMiwyLDIACgkQfj0C55Tb+AisVgEAue3WyVVGY7GBg1v3Zt8e eeD5pIl0nLnXPUEjlLTIJNUA/2WZU04Y/56uL4zU3y+755L6om2vsL3DmWWaCGB9 0zoN =7Raz -----END PGP SIGNATURE----- --o3jizhh4qfyisfpc--