Re: [PATCH v2 0/4] mm/zswap: Implement per-cgroup proactive writeback

[Andrew Morton]

On Mon, 25 May 2026 20:22:38 +0800 Hao Jia <jiahao.kernel@xxxxxxxxx> 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".