Re: [PATCH v3 2/2] mm/compaction: make proactive compaction high watermark configurable via sysctl
From: Vlastimil Babka
Date: Thu Jan 30 2025 - 09:18:45 EST
On 1/28/25 02:18, Andrew Morton wrote:
> On Mon, 27 Jan 2025 22:50:20 +0100 Michal Clapinski <mclapinski@xxxxxxxxxx> wrote:
>
>> Currently, the difference between the high and low watermarks for
>> proactive compaction is hardcoded to 10. This hardcoded difference is
>> too large for free page reporting to work well.
>>
>> Add a new sysctl, `compaction_proactiveness_leeway`, to control the
>> difference between the high and low watermarks.
>>
>
> Oh dear, yet another tunable. Is there any way in which we can
> acceptably improve the kernel without adding this?
compaction_proactiveness between 0 and 90 works as usual,
thus up to low watermark of 10 and high watermark of 20
compaction_proactiveness between 90 and 100 additionally reduces leeway,
with value of 100 resulting of low = high = 0
or some similar scheme, as long as a value of 100 does low = high = 0
It's rather arbitrary but AFAIU does what Michal needs and higher
proactiveness means more aggressive compaction.
Question is, would anyone else find it useful to have low_watermark of 0 and
high watermark of 10?