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

[Suren Baghdasaryan <surenb@google.com>]

On Tue, Sep 9, 2025 at 12:21 PM Shakeel Butt <shakeel.butt@linux.dev> wrote:
>
> 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?

SIGKILL

>
> > 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?

Yes, LMKD has a reaper thread which wakes up and calls
process_mrelease() after the main LMKD thread issued SIGKILL.

>