From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E8395C433DB for ; Tue, 2 Feb 2021 19:25:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD94864E46 for ; Tue, 2 Feb 2021 19:25:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239712AbhBBTZC (ORCPT ); Tue, 2 Feb 2021 14:25:02 -0500 Received: from mail.kernel.org ([198.145.29.99]:47950 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238091AbhBBTWt (ORCPT ); Tue, 2 Feb 2021 14:22:49 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 73A5260295; Tue, 2 Feb 2021 19:22:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1612293728; bh=rs9uwII8KyHK4Vkzu1J6iO7mDqwP1qE+rkY53pLfDnA=; h=Date:From:To:Subject:From; b=iK3fNfhRGBW4dc837w2dTDmWwJnUHDgnFqhGIPoQ5FoIeQKX8E0vVNbLAdmTDVT5o iqI2ln7m11ZL5GuEzmFmrawKClKwmnWwuG+hYvlEdhiOiz8iiJhyZE3ZBSQZfuoRnz Wxi4Q80vdAbaLbGac33FZTrFl4IReg5YK2/7/eoI= Date: Tue, 02 Feb 2021 11:22:07 -0800 From: akpm@linux-foundation.org To: hannes@cmpxchg.org, mm-commits@vger.kernel.org Subject: + mm-vmstat-fix-nohz-wakeups-for-node-stat-changes.patch added to -mm tree Message-ID: <20210202192207.rcIq2jj78%akpm@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: mm: vmstat: fix NOHZ wakeups for node stat changes has been added to the -mm tree. Its filename is mm-vmstat-fix-nohz-wakeups-for-node-stat-changes.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-vmstat-fix-nohz-wakeups-for-node-stat-changes.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-vmstat-fix-nohz-wakeups-for-node-stat-changes.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Johannes Weiner Subject: mm: vmstat: fix NOHZ wakeups for node stat changes On NOHZ, the periodic vmstat flushers on each CPU can go to sleep and won't wake up until stat changes are detected in the per-cpu deltas of the zone vmstat counters. In commit 75ef71840539 ("mm, vmstat: add infrastructure for per-node vmstats") per-node counters were introduced, and subsequently most stats were moved from the zone to the node level. However, the node counters weren't added to the NOHZ wakeup detection. In theory this can cause per-cpu errors to remain in the user-reported stats indefinitely. In practice this only affects a handful of sub counters (file_mapped, dirty and writeback e.g.) because other page state changes at the node level likely involve a change at the zone level as well (alloc and free, lru ops). Also, nobody has complained. Fix it up for completeness: wake up vmstat refreshing on node changes. Also remove the BUILD_BUG_ONs that assert counter size; we haven't relied on it since we added sizeof() to the range calculation in commit 13c9aaf7fa01 ("mm/vmstat.c: fix NUMA statistics updates"). Link: https://lkml.kernel.org/r/20210202184342.118513-1-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Signed-off-by: Andrew Morton --- mm/vmstat.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) --- a/mm/vmstat.c~mm-vmstat-fix-nohz-wakeups-for-node-stat-changes +++ a/mm/vmstat.c @@ -1894,16 +1894,12 @@ static void vmstat_update(struct work_st */ static bool need_update(int cpu) { + pg_data_t *last_pgdat = NULL; struct zone *zone; for_each_populated_zone(zone) { struct per_cpu_pageset *p = per_cpu_ptr(zone->pageset, cpu); - - BUILD_BUG_ON(sizeof(p->vm_stat_diff[0]) != 1); -#ifdef CONFIG_NUMA - BUILD_BUG_ON(sizeof(p->vm_numa_stat_diff[0]) != 2); -#endif - + struct per_cpu_nodestat *n; /* * The fast way of checking if there are any vmstat diffs. */ @@ -1915,6 +1911,13 @@ static bool need_update(int cpu) sizeof(p->vm_numa_stat_diff[0]))) return true; #endif + if (last_pgdat == zone->zone_pgdat) + continue; + last_pgdat = zone->zone_pgdat; + n = per_cpu_ptr(zone->zone_pgdat->per_cpu_nodestats, cpu); + if (memchr_inv(n->vm_node_stat_diff, 0, NR_VM_NODE_STAT_ITEMS * + sizeof(n->vm_node_stat_diff[0]))) + return true; } return false; } _ Patches currently in -mm which might be from hannes@cmpxchg.org are revert-mm-memcontrol-avoid-workload-stalls-when-lowering-memoryhigh.patch mm-vmstat-fix-nohz-wakeups-for-node-stat-changes.patch