[DISCUSS] Proposal: move slab shrinking into a dedicated kernel thread to improve reclaim efficiency

[Yifan Ji <412752700jyf@gmail.com>]

Hi all,

We've been profiling memory reclaim performance on mobile systems and found
that slab shrinking can dominate reclaim time, particularly when multiple
shrinkers are active. In some cases, shrink_slab() introduces noticeable
latency in both direct reclaim and kswapd contexts.

We are exploring an approach to move slab shrinking into a dedicated kernel
thread, decoupling it from direct reclaim and kswapd. The goal is to perform
slab reclaim asynchronously under controlled conditions such as idle periods
or vmpressure triggers.

Motivation:
 - Reduce latency in direct reclaim paths.
 - Improve reclaim efficiency by separating page and slab reclaim.
 - Provide more flexible scheduling for slab shrinking.

Proposed direction:
 - Introduce a kernel thread that periodically or conditionally calls
shrink_slab().

We'd appreciate feedback on:
 - Whether this decoupling aligns with the design of the current reclaim model.
 - Possible implications on fairness, concurrency, and memcg behavior.

Thanks for your time and input.

Best regards,
Yifan Ji