From: Michal Hocko <mhocko@kernel.org>
To: Balbir Singh <bsingharora@gmail.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
"John Hubbard" <jhubbard@nvidia.com>,
"David Nellans" <dnellans@nvidia.com>,
"Dan Williams" <dan.j.williams@intel.com>,
"Johannes Weiner" <hannes@cmpxchg.org>,
"Vladimir Davydov" <vdavydov.dev@gmail.com>,
"cgroups@vger.kernel.org" <cgroups@vger.kernel.org>
Subject: Re: [PATCH 4/5] mm/memcontrol: allow to uncharge page without using page->lru field
Date: Wed, 5 Jul 2017 08:38:14 +0200 [thread overview]
Message-ID: <20170705063813.GB10354@dhcp22.suse.cz> (raw)
In-Reply-To: <CAKTCnz=zTjYeqeTYZbnOMsT1Ccus4yW=jAws_OgXp3q4xmuSPA@mail.gmail.com>
On Wed 05-07-17 13:18:18, Balbir Singh wrote:
> On Tue, Jul 4, 2017 at 10:51 PM, Michal Hocko <mhocko@kernel.org> wrote:
> > On Mon 03-07-17 17:14:14, Jerome Glisse wrote:
> >> HMM pages (private or public device pages) are ZONE_DEVICE page and
> >> thus you can not use page->lru fields of those pages. This patch
> >> re-arrange the uncharge to allow single page to be uncharge without
> >> modifying the lru field of the struct page.
> >>
> >> There is no change to memcontrol logic, it is the same as it was
> >> before this patch.
> >
> > What is the memcg semantic of the memory? Why is it even charged? AFAIR
> > this is not a reclaimable memory. If yes how are we going to deal with
> > memory limits? What should happen if go OOM? Does killing an process
> > actually help to release that memory? Isn't it pinned by a device?
> >
> > For the patch itself. It is quite ugly but I haven't spotted anything
> > obviously wrong with it. It is the memcg semantic with this class of
> > memory which makes me worried.
> >
>
> This is the HMM CDM case. Memory is normally malloc'd and then
> migrated to ZONE_DEVICE or vice-versa. One of the things we did
> discuss was seeing ZONE_DEVICE memory in user page tables.
This doesn't answer any of the above questions though.
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2017-07-05 6:38 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-03 21:14 [PATCH 0/5] Cache coherent device memory (CDM) with HMM v3 Jérôme Glisse
2017-07-03 21:14 ` [PATCH 1/5] mm/persistent-memory: match IORES_DESC name and enum memory_type one Jérôme Glisse
2017-07-03 23:49 ` Dan Williams
2017-07-05 14:25 ` Jerome Glisse
2017-07-05 16:15 ` Dan Williams
2017-07-05 18:49 ` Jerome Glisse
2017-07-11 3:48 ` Balbir Singh
2017-07-11 7:31 ` Dan Williams
2017-07-11 15:05 ` Jerome Glisse
2017-07-11 16:49 ` Dan Williams
2017-07-03 21:14 ` [PATCH 2/5] mm/device-public-memory: device memory cache coherent with CPU v2 Jérôme Glisse
2017-07-11 4:12 ` Balbir Singh
2017-07-11 14:57 ` Jerome Glisse
2017-07-12 5:50 ` Balbir Singh
2017-07-03 21:14 ` [PATCH 3/5] mm/hmm: add new helper to hotplug CDM memory region Jérôme Glisse
2017-07-03 21:14 ` [PATCH 4/5] mm/memcontrol: allow to uncharge page without using page->lru field Jérôme Glisse
2017-07-04 12:51 ` Michal Hocko
2017-07-05 3:18 ` Balbir Singh
2017-07-05 6:38 ` Michal Hocko [this message]
2017-07-05 10:22 ` Balbir Singh
2017-07-05 14:35 ` Jerome Glisse
2017-07-10 8:28 ` Michal Hocko
2017-07-10 15:32 ` Jerome Glisse
2017-07-10 16:04 ` Michal Hocko
2017-07-10 16:25 ` Jerome Glisse
2017-07-10 16:36 ` Michal Hocko
2017-07-10 16:54 ` Jerome Glisse
2017-07-10 17:48 ` Michal Hocko
2017-07-10 18:10 ` Jerome Glisse
2017-07-03 21:14 ` [PATCH 5/5] mm/memcontrol: support MEMORY_DEVICE_PRIVATE and MEMORY_DEVICE_PUBLIC Jérôme Glisse
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