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[202.108.3.164]) by mx.google.com with SMTP id d1si1132567pjv.85.2019.05.23.08.51.38 for ; Thu, 23 May 2019 08:51:39 -0700 (PDT) Received-SPF: pass (google.com: domain of hdanton@sina.com designates 202.108.3.164 as permitted sender) client-ip=202.108.3.164; Authentication-Results: mx.google.com; spf=pass (google.com: domain of hdanton@sina.com designates 202.108.3.164 as permitted sender) smtp.mailfrom=hdanton@sina.com Received: from unknown (HELO localhost.localdomain)([114.253.229.186]) by sina.com with ESMTP id 5CE6C187000025A8; Thu, 23 May 2019 23:51:37 +0800 (CST) X-Sender: hdanton@sina.com X-Auth-ID: hdanton@sina.com X-SMAIL-MID: 321269394360 From: Hillf Danton To: Yang Shi Cc: ying.huang@intel.com, hannes@cmpxchg.org, mhocko@suse.com, mgorman@techsingularity.net, kirill.shutemov@linux.intel.com, josef@toxicpanda.com, hughd@google.com, shakeelb@google.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [v4 PATCH 2/2] mm: vmscan: correct some vmscan counters for THP swapout Date: Thu, 23 May 2019 23:51:26 +0800 Message-Id: <20190523155126.2312-1-hdanton@sina.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, 23 May 2019 10:27:38 +0800 Yang Shi wrote: > > @ -1642,14 +1650,14 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, > unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 }; > unsigned long nr_skipped[MAX_NR_ZONES] = { 0, }; > unsigned long skipped = 0; > - unsigned long scan, total_scan, nr_pages; > + unsigned long scan, total_scan; > + unsigned long nr_pages; Change for no earn:) > LIST_HEAD(pages_skipped); > isolate_mode_t mode = (sc->may_unmap ? 0 : ISOLATE_UNMAPPED); > > + total_scan = 0; > scan = 0; > - for (total_scan = 0; > - scan < nr_to_scan && nr_taken < nr_to_scan && !list_empty(src); > - total_scan++) { > + while (scan < nr_to_scan && !list_empty(src)) { > struct page *page; AFAICS scan currently prevents us from looping for ever, while nr_taken bails us out once we get what's expected, so I doubt it makes much sense to cut nr_taken off. > > page = lru_to_page(src); > @@ -1657,9 +1665,12 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, > > VM_BUG_ON_PAGE(!PageLRU(page), page); > > + nr_pages = 1 << compound_order(page); > + total_scan += nr_pages; > + > if (page_zonenum(page) > sc->reclaim_idx) { > list_move(&page->lru, &pages_skipped); > - nr_skipped[page_zonenum(page)]++; > + nr_skipped[page_zonenum(page)] += nr_pages; > continue; > } > > @@ -1669,10 +1680,9 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, > * ineligible pages. This causes the VM to not reclaim any > * pages, triggering a premature OOM. > */ > - scan++; > + scan += nr_pages; The comment looks to defy the change if we fail to add a huge page to the dst list; otherwise nr_taken knows how to do the right thing. What I prefer is to let scan to do one thing a time. > switch (__isolate_lru_page(page, mode)) { > case 0: > - nr_pages = hpage_nr_pages(page); > nr_taken += nr_pages; > nr_zone_taken[page_zonenum(page)] += nr_pages; > list_move(&page->lru, dst); > -- > 1.8.3.1 > Best Regards Hillf