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AJvYcCVuLZ6ba7zghBXFYj7CYtDpG1ZnHBjlYJkGNsSQ+0KicbhRMCf1CmTNxrOoLVKpusWQ8WJzvr1icw==@kvack.org X-Gm-Message-State: AOJu0YwRnFp2ZoHHKK3HzWOK1WXUxpTfDUK3v/tSeDrWupT7OBa03XI2 s9xXVPe9ahwTSeXVnjON/q4LaN+Q7gIllFT0fFnq0UOUMc4ydI9gQJknUVxpcroA6kciLZUmP4X svvH9ApSJWlmqRZmFdb8V9HwGtKM= X-Google-Smtp-Source: AGHT+IFwc4f5kyKAfJNVropwB7Maj3cXwYzRuG9QJBw+rGCgZmFQaltgr3CCdn3mYqSHswUhEmCCe+GqKdUxQ6zosuw= X-Received: by 2002:a05:6214:3187:b0:6cb:3643:3370 with SMTP id 6a1803df08f44-6cb3b5e8b2cmr27343926d6.23.1727392389141; Thu, 26 Sep 2024 16:13:09 -0700 (PDT) MIME-Version: 1.0 References: <20240926225531.700742-1-intelfx@intelfx.name> In-Reply-To: <20240926225531.700742-1-intelfx@intelfx.name> From: Nhat Pham Date: Thu, 26 Sep 2024 16:12:58 -0700 Message-ID: Subject: Re: [PATCH] zswap: improve memory.zswap.writeback inheritance To: Ivan Shapovalov Cc: linux-kernel@vger.kernel.org, Mike Yuan , Tejun Heo , Zefan Li , Johannes Weiner , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Jonathan Corbet , Yosry Ahmed , Chengming Zhou , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Chris Li , cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 0A4F6160010 X-Stat-Signature: 6wiqprkp85rppsz8cm7to4iubwtd9nzh X-Rspam-User: X-HE-Tag: 1727392389-866658 X-HE-Meta: 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 VeAfOTvy av/cSdRvUj/1WZaWJQvizEUGthDwkX0gUfEgh1G+vifPGGFPVN8wf/pf4T1VIuocw4K49LDrKQRH/1z5Dh/McYQVl40Iy8CMl9bIBDBfxSpfrIEFl/FopNM5Bh/HFlHbJRu6So+QvCbGOzMaW7vQutongI42UOWLrBAWB75fLQ4Dcm1TDiaraPihW2esBejMPkFA86z9TGLtFcGz1aWJ0ouiQ9QGKsCqwoNlPox2+WFYDgQtlXL9SvWlCyC0HqnrV7bwcEuP3z+Rqxgmc7Ekb21znDw5k6TaQihp2UYp5e4L511B64Z5wTX35s0+OxUt1l1+c X-Bogosity: Ham, tests=bogofilter, spamicity=0.019001, 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, Sep 26, 2024 at 3:55=E2=80=AFPM Ivan Shapovalov wrote: > > Improve the inheritance behavior of the `memory.zswap.writeback` cgroup > attribute introduced during the 6.11 cycle. Specifically, in 6.11 we > walk the parent cgroups until we find a _disabled_ writeback, which does > not allow the user to selectively enable zswap writeback while having it > disabled by default. Is there an actual need for this? This is a theoretical use case I thought of (and raised), but I don't think anybody actually wants this...? Besides, most people who want this can just: 1. Enable zswap writeback on root cgroup (and all non-leaf cgroups). 2. Disable zswap writeback on leaf cgroups on creation by default. 3. Selectively enable zswap writeback for the leaf cgroups. All of this is quite doable in userspace. It's not even _that_ racy - just do this before adding tasks etc. to the cgroup?