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From: David Hildenbrand <david@redhat.com>
To: Mel Gorman <mgorman@techsingularity.net>, Michal Hocko <mhocko@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Linux-MM <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Oscar Salvador <osalvador@suse.de>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Alexander Duyck <alexander.h.duyck@linux.intel.com>,
	Minchan Kim <minchan@kernel.org>
Subject: Re: [PATCH] mm/memory_hotplug: Make unpopulated zones PCP structures unreachable during hot remove
Date: Fri, 9 Apr 2021 21:05:25 +0200
Message-ID: <9317b74e-f706-27eb-6e5c-3dc0f3ee98b8@redhat.com> (raw)
In-Reply-To: <20210409151259.GP3697@techsingularity.net>

>>> zone_pcp_reset still needs to exist to drain the remaining vmstats or
>>> it'll break 5a883813845a ("memory-hotplug: fix zone stat
>>> mismatch").
>>
>> Are you sure we are reseting vmstats in the hotremove. I do not see
>> anything like that. Maybe this was needed at the time. I will double
>> check.
> 
> zone_pcp_reset calls drain_zonestat to apply the per-cpu vmstat deltas
> to the atomic per-zone and global stats.
> 
> If anything, the minimal "fix" is to simply delete IRQ disable/enable on
> the grounds that IRQs protect nothing and assume the existing hotplug
> paths guarantees the PCP cannot be used after zone_pcp_enable(). That

^ that sounds sane to me

> should be the case already because all the pages have been freed and
> there is nothing to even put into the PCPs but I worried that the PCP
> structure itself might still be reachable even if it's useless which is
> why I freed the structure once they could not be reached via zonelists.
> 


-- 
Thanks,

David / dhildenb


  reply index

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-09 12:09 Mel Gorman
2021-04-09 12:42 ` Michal Hocko
2021-04-09 12:48   ` Michal Hocko
2021-04-09 13:42     ` Mel Gorman
2021-04-09 14:37       ` Michal Hocko
2021-04-09 15:12         ` Mel Gorman
2021-04-09 19:05           ` David Hildenbrand [this message]
2021-04-10  7:25           ` Michal Hocko

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