Messages in this thread | | | Date | Tue, 17 Jan 2023 15:53:12 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH 1/3] mm: return the number of pages successfully paged out |
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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@kernel.org> 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.
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