Path: csiph.com!feeder.erje.net!2.us.feeder.erje.net!newsfeed.fsmpi.rwth-aachen.de!newsfeed.straub-nv.de!news.mixmin.net!aioe.org!bofh.it!news.nic.it!robomod From: Michal Hocko Newsgroups: linux.kernel Subject: [PATCH 5/3] mm, vmscan: make zone_reclaimable_pages more precise Date: Thu, 28 Jan 2016 22:20:02 +0100 Message-ID: References: X-Google-Dkim-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=xAdWX/jwvz1/iU3mKm//o9pq7XYjkm+H/ZHDVKzOJHw=; b=Q+ONY/cwTe23JlDXGaO7tPUqzpEB0KsztrDASiZgHsPGuoi0VbJQ7NETXGDI3N0frN yZ2+S4ibfGJKP/DeFNoi41yTOYDw5EVJDkmJg1AkXsV27OjkrzxzYSsFNnZLRef6G3IZ +09rGeO+dBR/MaeESQ7IPZWKwwbuDKJwN+fqRkKlTZXtan3RwkRunZgA5tl8xHQj4jIu MI2KN+YR3MUm9IKqwzvSvJa3KizmP0t+E1zdmlP5tVaAgm7bKo0G+H719m/JNkPAi1p1 gZUZh7FcEmXOMT8352L+6Bpcv43qcGBRAINTNPEMfbQmvJwwdXf9Gud7BVFUiqwHzVWE KNqw== X-Gm-Message-State: AG10YOT7gzTLyfegeeMxZwlzGjJEW4/BFJ85ijWMKwpNwqO01/SfxpV0929+Eotuu+NaUg== X-Received: by 10.28.90.133 with SMTP id o127mr5649521wmb.101.1454015992773; Thu, 28 Jan 2016 13:19:52 -0800 (PST) X-Mailer: git-send-email 2.7.0.rc3 Sender: robomod@news.nic.it List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Approved: robomod@news.nic.it Lines: 53 Organization: linux.* mail to news gateway X-Original-Cc: Linus Torvalds , Johannes Weiner , Mel Gorman , David Rientjes , Tetsuo Handa , Hillf Danton , KAMEZAWA Hiroyuki , , LKML , Michal Hocko X-Original-Date: Thu, 28 Jan 2016 22:19:39 +0100 X-Original-Message-ID: <1454015979-9985-1-git-send-email-mhocko@kernel.org> X-Original-References: <1450203586-10959-1-git-send-email-mhocko@kernel.org> X-Original-Sender: linux-kernel-owner@vger.kernel.org Xref: csiph.com linux.kernel:1321061 From: Michal Hocko zone_reclaimable_pages is used in should_reclaim_retry which uses it to calculate the target for the watermark check. This means that precise numbers are important for the correct decision. zone_reclaimable_pages uses zone_page_state which can contain stale data with per-cpu diffs not synced yet (the last vmstat_update might have run 1s in the past). Use zone_page_state_snapshot in zone_reclaimable_pages instead. None of the current callers is in a hot path where getting the precise value (which involves per-cpu iteration) would cause an unreasonable overhead. Suggested-by: David Rientjes Signed-off-by: Michal Hocko --- mm/vmscan.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 489212252cd6..9145e3f89eab 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -196,21 +196,21 @@ unsigned long zone_reclaimable_pages(struct zone *zone) { unsigned long nr; - nr = zone_page_state(zone, NR_ACTIVE_FILE) + - zone_page_state(zone, NR_INACTIVE_FILE) + - zone_page_state(zone, NR_ISOLATED_FILE); + nr = zone_page_state_snapshot(zone, NR_ACTIVE_FILE) + + zone_page_state_snapshot(zone, NR_INACTIVE_FILE) + + zone_page_state_snapshot(zone, NR_ISOLATED_FILE); if (get_nr_swap_pages() > 0) - nr += zone_page_state(zone, NR_ACTIVE_ANON) + - zone_page_state(zone, NR_INACTIVE_ANON) + - zone_page_state(zone, NR_ISOLATED_ANON); + nr += zone_page_state_snapshot(zone, NR_ACTIVE_ANON) + + zone_page_state_snapshot(zone, NR_INACTIVE_ANON) + + zone_page_state_snapshot(zone, NR_ISOLATED_ANON); return nr; } bool zone_reclaimable(struct zone *zone) { - return zone_page_state(zone, NR_PAGES_SCANNED) < + return zone_page_state_snapshot(zone, NR_PAGES_SCANNED) < zone_reclaimable_pages(zone) * 6; } -- 2.7.0.rc3