Re: [PATCH] mm: add maybe_lru_add_drain() that only drains when threshold is exceeded

[Rik van Riel]

On Thu, 2024-12-19 at 18:23 +0100, David Hildenbrand wrote:
> On 19.12.24 15:11, Rik van Riel wrote:
> > 
> > I think we need to free those pending pages at
> > some point. They can't accumulate there forever.
> > However, I am not sure where those points should
> > be.
> 
> The number of entries are limited, 

...
> folio_batch_add() drains if folio_batch_space() returns 0 (no slots
> left).
> 
> Apparently we have PAGEVEC_SIZE slots, which is 31 ... 31 * PAGE_SIZE
> stranded there.

Sure enough! That was the piece I was missing last night.

I guess we can get away with just draining these in the
reclaim and compaction paths, and not touch them the
rest of the time?

That could be a nice improvement in some situations.

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