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Date: Fri, 17 Feb 2017 14:45:55 +0900 From: Minchan Kim <minchan@...nel.org> To: Shaohua Li <shli@...com> CC: Johannes Weiner <hannes@...xchg.org>, <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>, <Kernel-team@...com>, <mhocko@...e.com>, <hughd@...gle.com>, <riel@...hat.com>, <mgorman@...hsingularity.net>, <akpm@...ux-foundation.org> Subject: Re: [PATCH V3 3/7] mm: reclaim MADV_FREE pages Hi Shaohua, On Thu, Feb 16, 2017 at 04:27:18PM -0800, Shaohua Li wrote: > On Thu, Feb 16, 2017 at 01:40:18PM -0500, Johannes Weiner wrote: > > On Tue, Feb 14, 2017 at 11:36:09AM -0800, Shaohua Li wrote: > > > @@ -1419,11 +1419,18 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, > > > VM_BUG_ON_PAGE(!PageSwapCache(page) && PageSwapBacked(page), > > > page); > > > > > > - if (!PageDirty(page) && (flags & TTU_LZFREE)) { > > > - /* It's a freeable page by MADV_FREE */ > > > - dec_mm_counter(mm, MM_ANONPAGES); > > > - rp->lazyfreed++; > > > - goto discard; > > > + if (flags & TTU_LZFREE) { > > > + if (!PageDirty(page)) { > > > + /* It's a freeable page by MADV_FREE */ > > > + dec_mm_counter(mm, MM_ANONPAGES); > > > + rp->lazyfreed++; > > > + goto discard; > > > + } else { > > > + set_pte_at(mm, address, pvmw.pte, pteval); > > > + ret = SWAP_FAIL; > > > + page_vma_mapped_walk_done(&pvmw); > > > + break; > > > + } > > > > I don't understand why we need the TTU_LZFREE bit in general. More on > > that below at the callsite. > > Sounds useless flag, don't see any reason we shouldn't free the MADV_FREE page > in places other than reclaim. Looks TTU_UNMAP is useless too.. Agree on TTU_UNMAP but for example, THP split doesn't mean free lazyfree pages, I think.
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