Re: [RESEND PATCH v7 6/8] mm: Add APIs to free a folio directly to the buddy bypassing pcp

[Byungchul Park]

On Thu, Feb 08, 2024 at 12:49:19PM -0800, Andrew Morton wrote:
> On Thu,  8 Feb 2024 15:26:06 +0900 Byungchul Park <byungchul@xxxxxx> wrote:
> 
> > This is a preparation for migrc mechanism that frees folios at a better
> 
> The term "migrc" appears in various places but I don't think we're told
> what is actually means?
> 
> > time later, rather than the moment migrating folios. The folios freed by
> > migrc are too old to keep in pcp.
> 
> How do we define "too old" and what causes you to believe this is the case?

Migrc defers folio_put() for source folios of migration that would be
unlikely used and frees a bunch of folios at once later. However, it
pollutes pcp, which means fresher folios might get free_pcppages_bulk()ed
and makes the effort to keep the best amount of pcp get unstable. So I
didn't want to make this situation happen.

	Byungchul