Re: [PATCH 0/2] Improve Zram by separating compression context from kswapd

[Nhat Pham]

On Fri, Mar 7, 2025 at 4:02 AM Qun-Wei Lin <qun-wei.lin@xxxxxxxxxxxx> wrote:
>
> This patch series introduces a new mechanism called kcompressd to
> improve the efficiency of memory reclaiming in the operating system. The
> main goal is to separate the tasks of page scanning and page compression
> into distinct processes or threads, thereby reducing the load on the
> kswapd thread and enhancing overall system performance under high memory
> pressure conditions.

Please excuse my ignorance, but from your cover letter I still don't
quite get what is the problem here? And how would decouple compression
and scanning help?

>
> Problem:
>  In the current system, the kswapd thread is responsible for both
>  scanning the LRU pages and compressing pages into the ZRAM. This
>  combined responsibility can lead to significant performance bottlenecks,

What bottleneck are we talking about? Is one stage slower than the other?

>  especially under high memory pressure. The kswapd thread becomes a
>  single point of contention, causing delays in memory reclaiming and
>  overall system performance degradation.
>
> Target:
>  The target of this invention is to improve the efficiency of memory
>  reclaiming. By separating the tasks of page scanning and page
>  compression into distinct processes or threads, the system can handle
>  memory pressure more effectively.

I'm not a zram maintainer, so I'm definitely not trying to stop this
patch. But whatever problem zram is facing will likely occur with
zswap too, so I'd like to learn more :)