Re: [PATCH] mm,thp: stop leaking unreleased file pages

[Hugh Dickins]

On Wed, 3 Jun 2020, Matthew Wilcox wrote:
> On Wed, May 27, 2020 at 02:28:10PM -0700, Hugh Dickins wrote:
> > Saying "source inspection" reminds me: there is another funny in there,
> > but I don't think it matters very much in practice, and might need
> > rather a lot of testing to justify any particular patch: where
> > page_cache_sync_readahead() asks for PAGE_SIZE pages!
> > 
> > "end - index" seems a more reasonable number to me: but then we
> > might find that reading ahead into the next huge extent had actually
> > been a useful optimization (and those readahead functions impose
> > their own caps, so PAGE_SIZE shouldn't work out too outrageously).
> 
> That readahead was only added in 99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0
> so it probably hasn't really been performance tested yet.

I can well imagine that an entirely new body of code, exercised
in the background by khugepaged, will not be a leading candidate for
performance comparisons - rightly so; but arguing that by the commit
being in the tree for only eight months seems... odd :)

Hugh