I'm all hung up on the naming of everything. > mm: return the number of pages successfully paged out This is a vague title - MM is a big place. Perhaps "mm/vmscan: ..." On Tue, 17 Jan 2023 15:16:30 -0800 Minchan Kim <minchan@xxxxxxxxxx> wrote: > The reclaim_pages MADV_PAGEOUT uses needs to return the number of > pages paged-out successfully, not only the number of reclaimed pages > in the operation because those pages paged-out successfully will be > reclaimed easily at the memory pressure due to asynchronous writeback > rotation(i.e., PG_reclaim with folio_rotate_reclaimable). So... what does "paged out" actually mean? "writeback to backing store was initiated"? From an application's point of view it means "no longer in page tables needs a fault to get it back", no? > This patch renames the reclaim_pages with paging_out(with hope that "page_out" or "pageout" would be better than "paging_out". > it's clear from operation point of view) and then adds a additional > stat in reclaim_stat to represent the number of paged-out but kept > in the memory for rotation on writeback completion. So it's the number of pages against which we have initiated writeback. Why not call it "nr_writeback" or similar? > With that stat, madvise_pageout can know how many pages were paged-out > successfully as well as reclaimed. The return value will be used for > statistics in next patch. > > ... > > -unsigned long reclaim_pages(struct list_head *folio_list) > +/* > + * paging_out - reclaim clean pages and write dirty pages into storage > + * @folio_list: pages for paging out > + * > + * paging_out() writes dirty pages to backing storage and/or reclaim > + * clean pages from memory. Returns the number of written/reclaimed pages. s/reclaim/reclaims/ "and/or" it vague - just "or", I think. "written/reclaimed" is vague. "number of reclaimed pages plus the number of pages against which writeback was initiated" is precise.
