Re: [PATCH v0 0/2] mm: swap: Gather swap entries and batch async release

[Shakeel Butt <shakeel.butt@linux.dev>]

On Tue, Sep 09, 2025 at 02:53:39PM +0800, Lei Liu wrote:
> 1. Problem Scenario
> On systems with ZRAM and swap enabled, simultaneous process exits create
> contention. The primary bottleneck occurs during swap entry release
> operations, causing exiting processes to monopolize CPU resources. This
> leads to scheduling delays for high-priority processes.
> 
> 2. Android Use Case
> During camera launch, LMKD terminates background processes to free memory.

How does LMKD trigger the kills? SIGKILL or cgroup.kill?

> Exiting processes compete for CPU cycles, delaying the camera preview
> thread and causing visible stuttering - directly impacting user
> experience.

Since the exit/kill is due to low memory situation, punting the memory
freeing to a low priority async mechanism will help in improving user
experience. Most probably the application (camera preview here) will get
into global reclaim and will compete for CPU with the async memory
freeing.

What we really need is faster memory freeing and we should explore all
possible ways. As others suggested fix/improve the bottleneck in the
memory freeing path. In addition I think we should explore parallelizing
this as well.

On Android, I suppose most of the memory is associated with single or
small set of processes and parallelizing memory freeing would be
challenging. BTW is LMKD using process_mrelease() to release the killed
process memory?