Re: [PATCH] mm: memcg: Use larger chunks for proactive reclaim

[Michal Koutný]

Hello.

On Wed, Jan 31, 2024 at 04:24:41PM +0000, "T.J. Mercier" <tjmercier@xxxxxxxxxx> wrote:
>  		reclaimed = try_to_free_mem_cgroup_pages(memcg,
> -					min(nr_to_reclaim - nr_reclaimed, SWAP_CLUSTER_MAX),
> +					max((nr_to_reclaim - nr_reclaimed) / 4,
> +					    (nr_to_reclaim - nr_reclaimed) % 4),

The 1/4 factor looks like magic. 

Commit 0388536ac291 says:
| In theory, the amount of reclaimed would be in [request, 2 * request).

Doesn't this suggest 1/2 as a better option? (I didn't pursue the
theory.)

Also IMO importantly, when nr_to_reclaim - nr_reclaimed is less than 8,
the formula gives arbitrary (unrelated to delta's magnitude) values.

Regards,
Michal

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