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 296C9C2BB48 for ; Tue, 15 Dec 2020 03:11:03 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A662B224BD for ; Tue, 15 Dec 2020 03:11:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A662B224BD Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 47FF78D0041; Mon, 14 Dec 2020 22:11:02 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 430698D001C; Mon, 14 Dec 2020 22:11:02 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 36D398D0041; Mon, 14 Dec 2020 22:11:02 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0096.hostedemail.com [216.40.44.96]) by kanga.kvack.org (Postfix) with ESMTP id 1E06B8D001C for ; Mon, 14 Dec 2020 22:11:02 -0500 (EST) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id E104B8249980 for ; Tue, 15 Dec 2020 03:11:01 +0000 (UTC) X-FDA: 77594039922.16.twist91_28062db27420 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin16.hostedemail.com (Postfix) with ESMTP id C4AA1100E6903 for ; Tue, 15 Dec 2020 03:11:01 +0000 (UTC) X-HE-Tag: twist91_28062db27420 X-Filterd-Recvd-Size: 11961 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf33.hostedemail.com (Postfix) with ESMTP for ; Tue, 15 Dec 2020 03:11:01 +0000 (UTC) Date: Mon, 14 Dec 2020 19:10:59 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1608001860; bh=TMczCVD+2JAhBewLJNat0oRtmqAB/EjmKhvAY0SeaRo=; h=From:To:Subject:In-Reply-To:From; b=r4NzGu1CcaPW4Fsn77p1CE/3J2/t9n3mjmJVHYmTypq+zjN4YWcmYE+oOV8qBwiOg Au6BOxmojmgkMQxXRpO9/KootBChMaXjHGDWyb2QnB3uaTwTtjNwcx+uqvsMSTdZIP sVxXzb0jqorQ1Yk9UhVREza575iq83z3aV91Ss2g= From: Andrew Morton To: akpm@linux-foundation.org, david@redhat.com, linux-mm@kvack.org, mhocko@suse.com, mm-commits@vger.kernel.org, osalvador@suse.de, torvalds@linux-foundation.org, vbabka@suse.cz Subject: [patch 129/200] mm, page_alloc: disable pcplists during memory offline Message-ID: <20201215031059.0AU1xa_py%akpm@linux-foundation.org> In-Reply-To: <20201214190237.a17b70ae14f129e2dca3d204@linux-foundation.org> User-Agent: s-nail v14.8.16 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: From: Vlastimil Babka Subject: mm, page_alloc: disable pcplists during memory offline Memory offlining relies on page isolation to guarantee a forward progress because pages cannot be reused while they are isolated. But the page isolation itself doesn't prevent from races while freed pages are stored on pcp lists and thus can be reused. This can be worked around by repeated draining of pcplists, as done by commit 968318261221 ("mm/memory_hotplug: drain per-cpu pages again during memory offline"). David and Michal would prefer that this race was closed in a way that callers of page isolation who need stronger guarantees don't need to repeatedly drain. David suggested disabling pcplists usage completely during page isolation, instead of repeatedly draining them. To achieve this without adding special cases in alloc/free fastpath, we can use the same approach as boot pagesets - when pcp->high is 0, any pcplist addition will be immediately flushed. The race can thus be closed by setting pcp->high to 0 and draining pcplists once, before calling start_isolate_page_range(). The draining will serialize after processes that already disabled interrupts and read the old value of pcp->high in free_unref_page_commit(), and processes that have not yet disabled interrupts, will observe pcp->high == 0 when they are rescheduled, and skip pcplists. This guarantees no stray pages on pcplists in zones where isolation happens. This patch thus adds zone_pcp_disable() and zone_pcp_enable() functions that page isolation users can call before start_isolate_page_range() and after unisolating (or offlining) the isolated pages. Also, drain_all_pages() is optimized to only execute on cpus where pcplists are not empty. The check can however race with a free to pcplist that has not yet increased the pcp->count from 0 to 1. Thus make the drain optionally skip the racy check and drain on all cpus, and use this option in zone_pcp_disable(). As we have to avoid external updates to high and batch while pcplists are disabled, we take pcp_batch_high_lock in zone_pcp_disable() and release it in zone_pcp_enable(). This also synchronizes multiple users of zone_pcp_disable()/enable(). Currently the only user of this functionality is offline_pages(). [vbabka@suse.cz: add comment, per David] Link: https://lkml.kernel.org/r/527480ef-ed72-e1c1-52a0-1c5b0113df45@suse.cz Link: https://lkml.kernel.org/r/20201111092812.11329-8-vbabka@suse.cz Signed-off-by: Vlastimil Babka Suggested-by: David Hildenbrand Suggested-by: Michal Hocko Reviewed-by: Oscar Salvador Reviewed-by: David Hildenbrand Acked-by: Michal Hocko Signed-off-by: Andrew Morton --- mm/internal.h | 2 + mm/memory_hotplug.c | 28 ++++++---------- mm/page_alloc.c | 73 +++++++++++++++++++++++++++++++++++------- mm/page_isolation.c | 6 +-- 4 files changed, 78 insertions(+), 31 deletions(-) --- a/mm/internal.h~mm-page_alloc-disable-pcplists-during-memory-offline +++ a/mm/internal.h @@ -204,6 +204,8 @@ extern void free_unref_page_list(struct extern void zone_pcp_update(struct zone *zone); extern void zone_pcp_reset(struct zone *zone); +extern void zone_pcp_disable(struct zone *zone); +extern void zone_pcp_enable(struct zone *zone); #if defined CONFIG_COMPACTION || defined CONFIG_CMA --- a/mm/memory_hotplug.c~mm-page_alloc-disable-pcplists-during-memory-offline +++ a/mm/memory_hotplug.c @@ -1491,17 +1491,21 @@ int __ref offline_pages(unsigned long st } node = zone_to_nid(zone); + /* + * Disable pcplists so that page isolation cannot race with freeing + * in a way that pages from isolated pageblock are left on pcplists. + */ + zone_pcp_disable(zone); + /* set above range as isolated */ ret = start_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE, MEMORY_OFFLINE | REPORT_FAILURE); if (ret) { reason = "failure to isolate range"; - goto failed_removal; + goto failed_removal_pcplists_disabled; } - drain_all_pages(zone); - arg.start_pfn = start_pfn; arg.nr_pages = nr_pages; node_states_check_changes_offline(nr_pages, zone, &arg); @@ -1551,20 +1555,8 @@ int __ref offline_pages(unsigned long st goto failed_removal_isolated; } - /* - * per-cpu pages are drained after start_isolate_page_range, but - * if there are still pages that are not free, make sure that we - * drain again, because when we isolated range we might have - * raced with another thread that was adding pages to pcp list. - * - * Forward progress should be still guaranteed because - * pages on the pcp list can only belong to MOVABLE_ZONE - * because has_unmovable_pages explicitly checks for - * PageBuddy on freed pages on other zones. - */ ret = test_pages_isolated(start_pfn, end_pfn, MEMORY_OFFLINE); - if (ret) - drain_all_pages(zone); + } while (ret); /* Mark all sections offline and remove free pages from the buddy. */ @@ -1580,6 +1572,8 @@ int __ref offline_pages(unsigned long st zone->nr_isolate_pageblock -= nr_pages / pageblock_nr_pages; spin_unlock_irqrestore(&zone->lock, flags); + zone_pcp_enable(zone); + /* removal success */ adjust_managed_page_count(pfn_to_page(start_pfn), -nr_pages); zone->present_pages -= nr_pages; @@ -1612,6 +1606,8 @@ int __ref offline_pages(unsigned long st failed_removal_isolated: undo_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE); memory_notify(MEM_CANCEL_OFFLINE, &arg); +failed_removal_pcplists_disabled: + zone_pcp_enable(zone); failed_removal: pr_debug("memory offlining [mem %#010llx-%#010llx] failed due to %s\n", (unsigned long long) start_pfn << PAGE_SHIFT, --- a/mm/page_alloc.c~mm-page_alloc-disable-pcplists-during-memory-offline +++ a/mm/page_alloc.c @@ -3026,13 +3026,16 @@ static void drain_local_pages_wq(struct } /* - * Spill all the per-cpu pages from all CPUs back into the buddy allocator. - * - * When zone parameter is non-NULL, spill just the single zone's pages. + * The implementation of drain_all_pages(), exposing an extra parameter to + * drain on all cpus. * - * Note that this can be extremely slow as the draining happens in a workqueue. + * drain_all_pages() is optimized to only execute on cpus where pcplists are + * not empty. The check for non-emptiness can however race with a free to + * pcplist that has not yet increased the pcp->count from 0 to 1. Callers + * that need the guarantee that every CPU has drained can disable the + * optimizing racy check. */ -void drain_all_pages(struct zone *zone) +void __drain_all_pages(struct zone *zone, bool force_all_cpus) { int cpu; @@ -3071,7 +3074,13 @@ void drain_all_pages(struct zone *zone) struct zone *z; bool has_pcps = false; - if (zone) { + if (force_all_cpus) { + /* + * The pcp.count check is racy, some callers need a + * guarantee that no cpu is missed. + */ + has_pcps = true; + } else if (zone) { pcp = per_cpu_ptr(zone->pageset, cpu); if (pcp->pcp.count) has_pcps = true; @@ -3104,6 +3113,18 @@ void drain_all_pages(struct zone *zone) mutex_unlock(&pcpu_drain_mutex); } +/* + * Spill all the per-cpu pages from all CPUs back into the buddy allocator. + * + * When zone parameter is non-NULL, spill just the single zone's pages. + * + * Note that this can be extremely slow as the draining happens in a workqueue. + */ +void drain_all_pages(struct zone *zone) +{ + __drain_all_pages(zone, false); +} + #ifdef CONFIG_HIBERNATION /* @@ -6316,6 +6337,18 @@ static void pageset_init(struct per_cpu_ pcp->batch = BOOT_PAGESET_BATCH; } +void __zone_set_pageset_high_and_batch(struct zone *zone, unsigned long high, + unsigned long batch) +{ + struct per_cpu_pageset *p; + int cpu; + + for_each_possible_cpu(cpu) { + p = per_cpu_ptr(zone->pageset, cpu); + pageset_update(&p->pcp, high, batch); + } +} + /* * Calculate and set new high and batch values for all per-cpu pagesets of a * zone, based on the zone's size and the percpu_pagelist_fraction sysctl. @@ -6323,8 +6356,6 @@ static void pageset_init(struct per_cpu_ static void zone_set_pageset_high_and_batch(struct zone *zone) { unsigned long new_high, new_batch; - struct per_cpu_pageset *p; - int cpu; if (percpu_pagelist_fraction) { new_high = zone_managed_pages(zone) / percpu_pagelist_fraction; @@ -6344,10 +6375,7 @@ static void zone_set_pageset_high_and_ba zone->pageset_high = new_high; zone->pageset_batch = new_batch; - for_each_possible_cpu(cpu) { - p = per_cpu_ptr(zone->pageset, cpu); - pageset_update(&p->pcp, new_high, new_batch); - } + __zone_set_pageset_high_and_batch(zone, new_high, new_batch); } void __meminit setup_zone_pageset(struct zone *zone) @@ -8742,6 +8770,27 @@ void __meminit zone_pcp_update(struct zo mutex_unlock(&pcp_batch_high_lock); } +/* + * Effectively disable pcplists for the zone by setting the high limit to 0 + * and draining all cpus. A concurrent page freeing on another CPU that's about + * to put the page on pcplist will either finish before the drain and the page + * will be drained, or observe the new high limit and skip the pcplist. + * + * Must be paired with a call to zone_pcp_enable(). + */ +void zone_pcp_disable(struct zone *zone) +{ + mutex_lock(&pcp_batch_high_lock); + __zone_set_pageset_high_and_batch(zone, 0, 1); + __drain_all_pages(zone, true); +} + +void zone_pcp_enable(struct zone *zone) +{ + __zone_set_pageset_high_and_batch(zone, zone->pageset_high, zone->pageset_batch); + mutex_unlock(&pcp_batch_high_lock); +} + void zone_pcp_reset(struct zone *zone) { unsigned long flags; --- a/mm/page_isolation.c~mm-page_alloc-disable-pcplists-during-memory-offline +++ a/mm/page_isolation.c @@ -174,9 +174,9 @@ __first_valid_page(unsigned long pfn, un * A call to drain_all_pages() after isolation can flush most of them. However * in some cases pages might still end up on pcp lists and that would allow * for their allocation even when they are in fact isolated already. Depending - * on how strong of a guarantee the caller needs, further drain_all_pages() - * might be needed (e.g. __offline_pages will need to call it after check for - * isolated range for a next retry). + * on how strong of a guarantee the caller needs, zone_pcp_disable/enable() + * might be used to flush and disable pcplist before isolation and enable after + * unisolation. * * Return: 0 on success and -EBUSY if any part of range cannot be isolated. */ _