From: Pavel Tatashin <pasha.tatashin@soleen.com>
To: Michal Hocko <mhocko@suse.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>, Vlastimil Babka <vbabka@suse.cz>,
Mel Gorman <mgorman@suse.de>
Subject: Re: [PATCH] mm/memory_hotplug: drain per-cpu pages again during memory offline
Date: Wed, 2 Sep 2020 10:31:48 -0400 [thread overview]
Message-ID: <CA+CK2bChfLLDikSzaD0kCkchxiRd0fzpyDEEpbzEh_7MEqhNgw@mail.gmail.com> (raw)
In-Reply-To: <20200902141057.GK4617@dhcp22.suse.cz>
> > > The fix is to try to drain per-cpu lists again after
> > > check_pages_isolated_cb() fails.
>
> Still trying to wrap my head around this but I think this is not a
> proper fix. It should be the page isolation to make sure no races are
> possible with the page freeing path.
>
As Bharata B Rao found in another thread, the problem was introduced
by this change:
c52e75935f8d: mm: remove extra drain pages on pcp list
So, the drain used to be tried every time with lru_add_drain_all();
Which, I think is excessive, as we start a thread per cpu to try to
drain and catch a rare race condition. With the proposed change we
drain again only when we find such a condition. Fixing it in
start_isolate_page_range means that we must somehow synchronize it
with the release_pages() which adds costs to runtime code, instead of
to hot-remove code.
Pasha
next prev parent reply other threads:[~2020-09-02 14:32 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-01 12:46 [PATCH] mm/memory_hotplug: drain per-cpu pages again during memory offline Pavel Tatashin
2020-09-01 18:37 ` David Rientjes
2020-09-02 14:01 ` Michal Hocko
2020-09-02 14:10 ` Michal Hocko
2020-09-02 14:31 ` Pavel Tatashin [this message]
2020-09-02 14:49 ` Vlastimil Babka
2020-09-02 14:08 ` Michal Hocko
2020-09-02 14:26 ` Pavel Tatashin
2020-09-02 14:55 ` Vlastimil Babka
2020-09-02 15:13 ` Michal Hocko
2020-09-02 15:40 ` Pavel Tatashin
2020-09-02 17:51 ` Vlastimil Babka
2020-09-03 6:38 ` Michal Hocko
2020-09-03 18:20 ` David Hildenbrand
2020-09-03 18:23 ` Pavel Tatashin
2020-09-03 18:31 ` David Hildenbrand
2020-09-04 7:02 ` Michal Hocko
2020-09-04 14:25 ` Pavel Tatashin
2020-09-07 7:26 ` Michal Hocko
2020-09-04 6:32 ` Vlastimil Babka
2020-09-03 7:07 ` Michal Hocko
2020-09-03 13:43 ` Pavel Tatashin
2020-09-03 13:50 ` Vlastimil Babka
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