From: Michal Hocko <mhocko@suse.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Pavel Tatashin <pasha.tatashin@soleen.com>,
David Hildenbrand <david@redhat.com>,
Oscar Salvador <osalvador@suse.de>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [PATCH 7/9] mm, page_alloc: move draining pcplists to page isolation users
Date: Mon, 5 Oct 2020 15:57:04 +0200 [thread overview]
Message-ID: <20201005135704.GC4555@dhcp22.suse.cz> (raw)
In-Reply-To: <20200922143712.12048-8-vbabka@suse.cz>
On Tue 22-09-20 16:37:10, Vlastimil Babka wrote:
> Currently, pcplists are drained during set_migratetype_isolate() which means
> once per pageblock processed start_isolate_page_range(). This is somewhat
> wasteful. Moreover, the callers might need different guarantees, and the
> draining is currently prone to races and does not guarantee that no page
> from isolated pageblock will end up on the pcplist after the drain.
>
> Better guarantees are added by later patches and require explicit actions
> by page isolation users that need them. Thus it makes sense to move the
> current imperfect draining to the callers also as a preparation step.
>
> Suggested-by: Pavel Tatashin <pasha.tatashin@soleen.com>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
> ---
> mm/memory_hotplug.c | 11 ++++++-----
> mm/page_alloc.c | 2 ++
> mm/page_isolation.c | 10 +++++-----
> 3 files changed, 13 insertions(+), 10 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 9db80ee29caa..08f729922e18 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1524,6 +1524,8 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
> goto failed_removal;
> }
>
> + drain_all_pages(zone);
> +
> arg.start_pfn = start_pfn;
> arg.nr_pages = nr_pages;
> node_states_check_changes_offline(nr_pages, zone, &arg);
> @@ -1574,11 +1576,10 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
> }
>
> /*
> - * per-cpu pages are drained in 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.
> + * 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
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 901907799bdc..4e37bc3f6077 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8432,6 +8432,8 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> if (ret)
> return ret;
>
> + drain_all_pages(cc.zone);
> +
> /*
> * In case of -EBUSY, we'd like to know which page causes problem.
> * So, just fall through. test_pages_isolated() has a tracepoint
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index abfe26ad59fd..57d8bc1e7760 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -49,7 +49,6 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_
>
> __mod_zone_freepage_state(zone, -nr_pages, mt);
> spin_unlock_irqrestore(&zone->lock, flags);
> - drain_all_pages(zone);
> return 0;
> }
>
> @@ -167,11 +166,12 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
> *
> * Please note that there is no strong synchronization with the page allocator
> * either. Pages might be freed while their page blocks are marked ISOLATED.
> - * In some cases pages might still end up on pcp lists and that would allow
> + * 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 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, 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).
> *
> * Return: 0 on success and -EBUSY if any part of range cannot be isolated.
> */
> --
> 2.28.0
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2020-10-05 13:57 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-22 14:37 [PATCH 0/9] disable pcplists during memory offline Vlastimil Babka
2020-09-22 14:37 ` [PATCH 1/9] mm, page_alloc: clean up pageset high and batch update Vlastimil Babka
2020-09-25 10:18 ` David Hildenbrand
2020-10-05 12:03 ` Michal Hocko
2020-09-22 14:37 ` [PATCH 2/9] mm, page_alloc: calculate pageset high and batch once per zone Vlastimil Babka
2020-10-05 12:52 ` Michal Hocko
2020-10-06 22:04 ` Vlastimil Babka
2020-09-22 14:37 ` [PATCH 3/9] mm, page_alloc: remove setup_pageset() Vlastimil Babka
2020-09-25 10:19 ` David Hildenbrand
2020-10-05 12:59 ` Michal Hocko
2020-10-06 22:11 ` Vlastimil Babka
2020-09-22 14:37 ` [PATCH 4/9] mm, page_alloc: simplify pageset_update() Vlastimil Babka
2020-09-25 10:23 ` David Hildenbrand
2020-10-05 13:20 ` Michal Hocko
2020-09-22 14:37 ` [PATCH 5/9] mm, page_alloc: make per_cpu_pageset accessible only after init Vlastimil Babka
2020-09-25 10:25 ` David Hildenbrand
2020-10-05 13:24 ` Michal Hocko
2020-10-06 22:28 ` Vlastimil Babka
2020-09-22 14:37 ` [PATCH 6/9] mm, page_alloc: cache pageset high and batch in struct zone Vlastimil Babka
2020-09-25 10:34 ` David Hildenbrand
2020-10-06 22:31 ` Vlastimil Babka
2020-10-05 13:28 ` Michal Hocko
2020-10-06 22:34 ` Vlastimil Babka
2020-09-22 14:37 ` [PATCH 7/9] mm, page_alloc: move draining pcplists to page isolation users Vlastimil Babka
2020-09-25 10:39 ` David Hildenbrand
2020-10-05 13:57 ` Michal Hocko [this message]
2020-09-22 14:37 ` [PATCH 8/9] mm, page_alloc: drain all pcplists during memory offline Vlastimil Babka
2020-09-25 10:46 ` David Hildenbrand
2020-10-05 14:03 ` Michal Hocko
2020-09-22 14:37 ` [PATCH 9/9] mm, page_alloc: optionally disable pcplists during page isolation Vlastimil Babka
2020-09-25 10:53 ` David Hildenbrand
2020-09-25 10:54 ` David Hildenbrand
2020-09-25 11:10 ` Vlastimil Babka
2020-10-01 8:47 ` David Hildenbrand
2020-10-05 14:05 ` Michal Hocko
2020-10-05 14:22 ` Vlastimil Babka
2020-10-05 16:56 ` Michal Hocko
2020-10-06 8:34 ` Michal Hocko
2020-10-06 8:40 ` David Hildenbrand
2020-10-06 10:05 ` Michal Hocko
2020-09-22 17:15 ` [PATCH 0/9] disable pcplists during memory offline David Hildenbrand
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