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
