Re: [PATCH v3 0/2] mm/compaction: allow more aggressive proactive compaction

[Andrew Morton]

On Mon, 27 Jan 2025 22:50:18 +0100 Michal Clapinski <mclapinski@xxxxxxxxxx> wrote:

> Our goal is to keep memory usage of a VM low on the host. For that
> reason, we use free page reporting which by default reports free pages
> of order 9 and larger to the host to be freed. The feature works well
> only if the memory in the guest is not fragmented below pages of order
> 9. Proactive compaction can be reused to achieve defragmentation after
> some parameter tweaking.
> 
> When the fragmentation score (lower is better) gets larger than the
> high watermark, proactive compaction kicks in. Compaction stops when
> the score goes below the low watermark (or no progress is made and
> backoff kicks in). Let's define the difference between high and low
> watermarks as leeway. Before these changes, the minimum possible value
> for low watermark was 5 and the leeway was hardcoded to 10 (so minimum
> possible value for high watermark was 15).
> 

I'm not seeing enthusiasm for these changes and a couple of comments
from myself remain unaddressed.  I'll drop the series - let's revisit
in the next -rc cycle, if you feel so motivated.