From: Mel Gorman <mgorman@techsingularity.net>
To: David Hildenbrand <david@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Oscar Salvador <osalvador@suse.de>,
"Michael S. Tsirkin" <mst@redhat.com>,
Alexander Duyck <alexanderduyck@fb.com>,
Minchan Kim <minchan@kernel.org>, Michal Hocko <mhocko@suse.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 resend] mm/memory_hotplug: Make unpopulated zones PCP structures unreachable during hot remove
Date: Mon, 12 Apr 2021 16:27:37 +0100 [thread overview]
Message-ID: <20210412152737.GB3697@techsingularity.net> (raw)
In-Reply-To: <a0d73ce0-b2bd-1928-539d-39cb9da9bf1f@redhat.com>
On Mon, Apr 12, 2021 at 04:12:11PM +0200, David Hildenbrand wrote:
> > After v1 of the patch, the race was reduced to the point between the
> > zone watermark check and the rmqueue_pcplist but yes, it still existed.
> > Closing it completely was either complex or expensive. Setting
> > zone->pageset = &boot_pageset before the free would shrink the race
> > further but that still leaves a potential memory ordering issue.
> >
> > While fixable, it's either complex, expensive or both so yes, just leaving
> > the pageset structures in place would be much more straight-forward
> > assuming the structures were not allocated in the zone that is being
> > hot-removed. As things stand, I had trouble even testing zone hot-remove
> > as there was always a few pages left behind and I did not chase down
> > why.
>
> Can you elaborate? I can reliably trigger zone present pages going to 0 by
> just hotplugging a DIMM, onlining the memory block devices to the MOVABLE
> zone, followed by offlining the memory block again.
>
For the machine I was testing on, I tried offlining all memory within
a zone on a NUMA machine. Even if I used movable_zone to create a zone
or numa=fake to create multiple fake nodes and zones, there was always
either reserved or pinned pages preventing the full zone being removed.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2021-04-12 15:27 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-12 12:08 [PATCH v2 resend] mm/memory_hotplug: Make unpopulated zones PCP structures unreachable during hot remove Mel Gorman
2021-04-12 12:12 ` David Hildenbrand
2021-04-12 12:40 ` Vlastimil Babka
2021-04-12 14:08 ` Mel Gorman
2021-04-12 14:12 ` David Hildenbrand
2021-04-12 15:27 ` Mel Gorman [this message]
2021-04-12 16:02 ` David Hildenbrand
2021-04-13 9:36 ` Vlastimil Babka
2021-04-13 9:49 ` Mel Gorman
2021-04-13 10:16 ` Michal Hocko
2021-04-13 6:44 ` Michal Hocko
2021-04-13 6:40 ` Michal Hocko
2021-04-14 7:18 ` Oscar Salvador
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210412152737.GB3697@techsingularity.net \
--to=mgorman@techsingularity.net \
--cc=akpm@linux-foundation.org \
--cc=alexanderduyck@fb.com \
--cc=david@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@suse.com \
--cc=minchan@kernel.org \
--cc=mst@redhat.com \
--cc=osalvador@suse.de \
--cc=vbabka@suse.cz \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).