From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751938AbdBFMYm (ORCPT ); Mon, 6 Feb 2017 07:24:42 -0500 Received: from smtp.codeaurora.org ([198.145.29.96]:49766 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751694AbdBFMYk (ORCPT ); Mon, 6 Feb 2017 07:24:40 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 00300607CE Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=vinmenon@codeaurora.org From: Vinayak Menon To: akpm@linux-foundation.org, hannes@cmpxchg.org, mgorman@techsingularity.net, vbabka@suse.cz, mhocko@suse.com, riel@redhat.com, vdavydov.dev@gmail.com, anton.vorontsov@linaro.org, minchan@kernel.org, shashim@codeaurora.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vinayak Menon Subject: [PATCH 1/2 v4] mm: vmscan: do not pass reclaimed slab to vmpressure Date: Mon, 6 Feb 2017 17:54:09 +0530 Message-Id: <1486383850-30444-1-git-send-email-vinmenon@codeaurora.org> X-Mailer: git-send-email 1.8.2.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org During global reclaim, the nr_reclaimed passed to vmpressure includes the pages reclaimed from slab. But the corresponding scanned slab pages is not passed. This can cause total reclaimed pages to be greater than scanned, causing an unsigned underflow in vmpressure resulting in a critical event being sent to root cgroup. It was also noticed that, apart from the underflow, there is an impact to the vmpressure values because of this. While moving from kernel version 3.18 to 4.4, a difference is seen in the vmpressure values for the same workload resulting in a different behaviour of the vmpressure consumer. One such case is of a vmpressure based lowmemorykiller. It is observed that the vmpressure events are received late and less in number resulting in tasks not being killed at the right time. The following numbers show the impact on reclaim activity due to the change in behaviour of lowmemorykiller on a 4GB device. The test launches a number of apps in sequence and repeats it multiple times. v4.4 v3.18 pgpgin 163016456 145617236 pgpgout 4366220 4188004 workingset_refault 29857868 26781854 workingset_activate 6293946 5634625 pswpin 1327601 1133912 pswpout 3593842 3229602 pgalloc_dma 99520618 94402970 pgalloc_normal 104046854 98124798 pgfree 203772640 192600737 pgmajfault 2126962 1851836 pgsteal_kswapd_dma 19732899 18039462 pgsteal_kswapd_normal 19945336 17977706 pgsteal_direct_dma 206757 131376 pgsteal_direct_normal 236783 138247 pageoutrun 116622 108370 allocstall 7220 4684 compact_stall 931 856 This is a regression introduced by commit 6b4f7799c6a5 ("mm: vmscan: invoke slab shrinkers from shrink_zone()"). So do not consider reclaimed slab pages for vmpressure calculation. The reclaimed pages from slab can be excluded because the freeing of a page by slab shrinking depends on each slab's object population, making the cost model (i.e. scan:free) different from that of LRU. Also, not every shrinker accounts the pages it reclaims. Fixes: 6b4f7799c6a5 ("mm: vmscan: invoke slab shrinkers from shrink_zone()") Acked-by: Minchan Kim Cc: Johannes Weiner Cc: Mel Gorman Cc: Vlastimil Babka Cc: Michal Hocko Cc: Rik van Riel Cc: Vladimir Davydov Cc: Anton Vorontsov Cc: Shiraz Hashim Signed-off-by: Vinayak Menon --- mm/vmscan.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 947ab6f..8969f8e 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2594,16 +2594,23 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc) sc->nr_scanned - nr_scanned, node_lru_pages); + /* + * Record the subtree's reclaim efficiency. The reclaimed + * pages from slab is excluded here because the corresponding + * scanned pages is not accounted. Moreover, freeing a page + * by slab shrinking depends on each slab's object population, + * making the cost model (i.e. scan:free) different from that + * of LRU. + */ + vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true, + sc->nr_scanned - nr_scanned, + sc->nr_reclaimed - nr_reclaimed); + if (reclaim_state) { sc->nr_reclaimed += reclaim_state->reclaimed_slab; reclaim_state->reclaimed_slab = 0; } - /* Record the subtree's reclaim efficiency */ - vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true, - sc->nr_scanned - nr_scanned, - sc->nr_reclaimed - nr_reclaimed); - if (sc->nr_reclaimed - nr_reclaimed) reclaimable = true; -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id D79916B0033 for ; Mon, 6 Feb 2017 07:24:40 -0500 (EST) Received: by mail-pf0-f199.google.com with SMTP id f144so104109364pfa.3 for ; Mon, 06 Feb 2017 04:24:40 -0800 (PST) Received: from smtp.codeaurora.org (smtp.codeaurora.org. [198.145.29.96]) by mx.google.com with ESMTPS id o33si541780plb.159.2017.02.06.04.24.39 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 06 Feb 2017 04:24:39 -0800 (PST) From: Vinayak Menon Subject: [PATCH 1/2 v4] mm: vmscan: do not pass reclaimed slab to vmpressure Date: Mon, 6 Feb 2017 17:54:09 +0530 Message-Id: <1486383850-30444-1-git-send-email-vinmenon@codeaurora.org> Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org, hannes@cmpxchg.org, mgorman@techsingularity.net, vbabka@suse.cz, mhocko@suse.com, riel@redhat.com, vdavydov.dev@gmail.com, anton.vorontsov@linaro.org, minchan@kernel.org, shashim@codeaurora.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vinayak Menon During global reclaim, the nr_reclaimed passed to vmpressure includes the pages reclaimed from slab. But the corresponding scanned slab pages is not passed. This can cause total reclaimed pages to be greater than scanned, causing an unsigned underflow in vmpressure resulting in a critical event being sent to root cgroup. It was also noticed that, apart from the underflow, there is an impact to the vmpressure values because of this. While moving from kernel version 3.18 to 4.4, a difference is seen in the vmpressure values for the same workload resulting in a different behaviour of the vmpressure consumer. One such case is of a vmpressure based lowmemorykiller. It is observed that the vmpressure events are received late and less in number resulting in tasks not being killed at the right time. The following numbers show the impact on reclaim activity due to the change in behaviour of lowmemorykiller on a 4GB device. The test launches a number of apps in sequence and repeats it multiple times. v4.4 v3.18 pgpgin 163016456 145617236 pgpgout 4366220 4188004 workingset_refault 29857868 26781854 workingset_activate 6293946 5634625 pswpin 1327601 1133912 pswpout 3593842 3229602 pgalloc_dma 99520618 94402970 pgalloc_normal 104046854 98124798 pgfree 203772640 192600737 pgmajfault 2126962 1851836 pgsteal_kswapd_dma 19732899 18039462 pgsteal_kswapd_normal 19945336 17977706 pgsteal_direct_dma 206757 131376 pgsteal_direct_normal 236783 138247 pageoutrun 116622 108370 allocstall 7220 4684 compact_stall 931 856 This is a regression introduced by commit 6b4f7799c6a5 ("mm: vmscan: invoke slab shrinkers from shrink_zone()"). So do not consider reclaimed slab pages for vmpressure calculation. The reclaimed pages from slab can be excluded because the freeing of a page by slab shrinking depends on each slab's object population, making the cost model (i.e. scan:free) different from that of LRU. Also, not every shrinker accounts the pages it reclaims. Fixes: 6b4f7799c6a5 ("mm: vmscan: invoke slab shrinkers from shrink_zone()") Acked-by: Minchan Kim Cc: Johannes Weiner Cc: Mel Gorman Cc: Vlastimil Babka Cc: Michal Hocko Cc: Rik van Riel Cc: Vladimir Davydov Cc: Anton Vorontsov Cc: Shiraz Hashim Signed-off-by: Vinayak Menon --- mm/vmscan.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 947ab6f..8969f8e 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2594,16 +2594,23 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc) sc->nr_scanned - nr_scanned, node_lru_pages); + /* + * Record the subtree's reclaim efficiency. The reclaimed + * pages from slab is excluded here because the corresponding + * scanned pages is not accounted. Moreover, freeing a page + * by slab shrinking depends on each slab's object population, + * making the cost model (i.e. scan:free) different from that + * of LRU. + */ + vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true, + sc->nr_scanned - nr_scanned, + sc->nr_reclaimed - nr_reclaimed); + if (reclaim_state) { sc->nr_reclaimed += reclaim_state->reclaimed_slab; reclaim_state->reclaimed_slab = 0; } - /* Record the subtree's reclaim efficiency */ - vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true, - sc->nr_scanned - nr_scanned, - sc->nr_reclaimed - nr_reclaimed); - if (sc->nr_reclaimed - nr_reclaimed) reclaimable = true; -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org