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Thu, 23 Apr 2020 13:00:22 -0700 (PDT) Date: Thu, 23 Apr 2020 13:00:20 -0700 From: Minchan Kim To: Johannes Weiner Cc: Jaewon Kim , mgorman@suse.de, m.szyprowski@samsung.com, mina86@mina86.com, shli@fb.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, jaewon31.kim@gmail.com, ytk.lee@samsung.com Subject: Re: [PATCH v2] mm/vmscan: count layzfree pages and fix nr_isolated_* mismatch Message-ID: <20200423200020.GB46847@google.com> References: <20200422084815.21913-1-jaewon31.kim@samsung.com> <20200422130751.GD358439@cmpxchg.org> <5EA10872.3010500@samsung.com> <20200423160546.GA389168@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200423160546.GA389168@cmpxchg.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 23, 2020 at 12:05:46PM -0400, Johannes Weiner wrote: > On Thu, Apr 23, 2020 at 12:16:02PM +0900, Jaewon Kim wrote: > > > > > > On 2020년 04월 22일 22:07, Johannes Weiner wrote: > > > On Wed, Apr 22, 2020 at 05:48:15PM +0900, Jaewon Kim wrote: > > >> @@ -1295,11 +1295,15 @@ static unsigned long shrink_page_list(struct list_head *page_list, > > >> */ > > >> if (page_mapped(page)) { > > >> enum ttu_flags flags = ttu_flags | TTU_BATCH_FLUSH; > > >> + bool lazyfree = PageAnon(page) && !PageSwapBacked(page); > > >> > > >> if (unlikely(PageTransHuge(page))) > > >> flags |= TTU_SPLIT_HUGE_PMD; > > >> + > > >> if (!try_to_unmap(page, flags)) { > > >> stat->nr_unmap_fail += nr_pages; > > >> + if (lazyfree && PageSwapBacked(page)) > > > This looks pretty strange, until you remember that try_to_unmap() > > > could SetPageSwapbacked again. > > > > > > This might be more obvious? > > > > > > was_swapbacked = PageSwapBacked(page); > > > if (!try_to_unmap(page, flags)) { > > > stat->nr_unmap_fail += nr_pages; > > > if (!was_swapbacked && PageSwapBacked(page)) > > Hello Johannes, thank you for your comment. > > > > The name can changed from layzyfree to was_swapbacked. > > By the way, did you mean removing PageAnon(page), too? It seems to be OK, though. > > I can't decide whether PageAnon() makes it clearer or not. But it's > not really needed for correctness. So feel free to keep what you had. Yub, PageAnon is redundant. > I would really just at least change bool lazyfree to was_lazyfree, It's better.