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Date: Mon, 25 May 2026 12:24:24 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Hao Jia <jiahao.kernel@gmail.com>
Cc: tj@kernel.org, hannes@cmpxchg.org, shakeel.butt@linux.dev,
 mhocko@kernel.org, yosry@kernel.org, mkoutny@suse.com, 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 <jiahao1@lixiang.com>
Subject: Re: [PATCH v2 0/4] mm/zswap: Implement per-cgroup proactive
 writeback
Message-Id: <20260525122424.3b2818f06832d9d55da8d69b@linux-foundation.org>
In-Reply-To: <20260525122242.36127-1-jiahao.kernel@gmail.com>
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On Mon, 25 May 2026 20:22:38 +0800 Hao Jia <jiahao.kernel@gmail.com> wrote:

> Zswap currently writes back pages to backing swap reactively, triggered
> either by the shrinker or by the pool reaching its size limit. Although
> proactive memory reclaim can automatically write back a portion of zswap
> pages via the shrinker, it cannot explicitly control the amount of
> writeback for a specific memory cgroup. Moreover, proactive memory reclaim
> may not always be triggered during a steady state.
> 
> 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.
> 
> This patch series introduces a "zswap_writeback_only" key to memory.reclaim
> cgroup interface, allowing users to proactively write back cold compressed
> pages from zswap to the backing swap device. When specified, this key
> bypasses standard memory reclaim and exclusively performs proactive zswap
> writeback up to the requested budget. If omitted, the default reclaim
> behavior remains unchanged.

Thanks.  AI review found a few things to complain about, one of them
described as "preexisting".