From: Michal Hocko <mhocko@kernel.org>
To: Alexander Duyck <alexander.duyck@gmail.com>
Cc: virtio-dev@lists.oasis-open.org, kvm list <kvm@vger.kernel.org>,
"Michael S. Tsirkin" <mst@redhat.com>,
Catalin Marinas <catalin.marinas@arm.com>,
David Hildenbrand <david@redhat.com>,
Dave Hansen <dave.hansen@intel.com>,
LKML <linux-kernel@vger.kernel.org>,
Matthew Wilcox <willy@infradead.org>,
linux-mm <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
will@kernel.org, linux-arm-kernel@lists.infradead.org,
Oscar Salvador <osalvador@suse.de>,
Yang Zhang <yang.zhang.wz@gmail.com>,
Pankaj Gupta <pagupta@redhat.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Nitesh Narayan Lal <nitesh@redhat.com>,
Rik van Riel <riel@surriel.com>,
lcapitulino@redhat.com, "Wang, Wei W" <wei.w.wang@intel.com>,
Andrea Arcangeli <aarcange@redhat.com>,
ying.huang@intel.com, Paolo Bonzini <pbonzini@redhat.com>,
Dan Williams <dan.j.williams@intel.com>,
Fengguang Wu <fengguang.wu@intel.com>,
Alexander Duyck <alexander.h.duyck@linux.intel.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH v9 0/8] stg mail -e --version=v9 \
Date: Tue, 10 Sep 2019 16:47:13 +0200 [thread overview]
Message-ID: <20190910144713.GF2063@dhcp22.suse.cz> (raw)
In-Reply-To: <CAKgT0Udr6nYQFTRzxLbXk41SiJ-pcT_bmN1j1YR4deCwdTOaUQ@mail.gmail.com>
On Tue 10-09-19 07:42:43, Alexander Duyck wrote:
> On Tue, Sep 10, 2019 at 5:42 AM Michal Hocko <mhocko@kernel.org> wrote:
> >
> > I wanted to review "mm: Introduce Reported pages" just realize that I
> > have no clue on what is going on so returned to the cover and it didn't
> > really help much. I am completely unfamiliar with virtio so please bear
> > with me.
> >
> > On Sat 07-09-19 10:25:03, Alexander Duyck wrote:
> > [...]
> > > This series provides an asynchronous means of reporting to a hypervisor
> > > that a guest page is no longer in use and can have the data associated
> > > with it dropped. To do this I have implemented functionality that allows
> > > for what I am referring to as unused page reporting
> > >
> > > The functionality for this is fairly simple. When enabled it will allocate
> > > statistics to track the number of reported pages in a given free area.
> > > When the number of free pages exceeds this value plus a high water value,
> > > currently 32, it will begin performing page reporting which consists of
> > > pulling pages off of free list and placing them into a scatter list. The
> > > scatterlist is then given to the page reporting device and it will perform
> > > the required action to make the pages "reported", in the case of
> > > virtio-balloon this results in the pages being madvised as MADV_DONTNEED
> > > and as such they are forced out of the guest. After this they are placed
> > > back on the free list,
> >
> > And here I am reallly lost because "forced out of the guest" makes me
> > feel that those pages are no longer usable by the guest. So how come you
> > can add them back to the free list. I suspect understanding this part
> > will allow me to understand why we have to mark those pages and prevent
> > merging.
>
> Basically as the paragraph above mentions "forced out of the guest"
> really is just the hypervisor calling MADV_DONTNEED on the page in
> question. So the behavior is the same as any userspace application
> that calls MADV_DONTNEED where the contents are no longer accessible
> from userspace and attempting to access them will result in a fault
> and the page being populated with a zero fill on-demand page, or a
> copy of the file contents if the memory is file backed.
As I've said I have no idea about virt so this doesn't really tell me
much. Does that mean that if somebody allocates such a page and tries to
access it then virt will handle a fault and bring it back?
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-09-10 14:47 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-07 17:25 [PATCH v9 0/8] stg mail -e --version=v9 \ Alexander Duyck
2019-09-07 17:25 ` [PATCH v9 1/8] mm: Add per-cpu logic to page shuffling Alexander Duyck
2019-09-09 8:14 ` David Hildenbrand
2019-09-09 15:11 ` Alexander Duyck
2019-09-10 12:11 ` Michal Hocko
2019-09-10 22:14 ` Alexander Duyck
2019-09-10 22:11 ` Alexander Duyck
2019-09-09 9:07 ` Kirill A. Shutemov
2019-09-09 15:12 ` Alexander Duyck
2019-09-07 17:25 ` [PATCH v9 2/8] mm: Adjust shuffle code to allow for future coalescing Alexander Duyck
2019-09-09 8:19 ` David Hildenbrand
2019-09-09 9:47 ` Kirill A. Shutemov
2019-09-09 15:22 ` Alexander Duyck
2019-09-09 15:35 ` Kirill A. Shutemov
2019-09-09 15:37 ` Alexander Duyck
2019-09-09 16:43 ` Alexander Duyck
2019-09-09 17:00 ` Kirill A. Shutemov
2019-09-10 12:20 ` Michal Hocko
2019-09-10 14:48 ` Alexander Duyck
2019-09-07 17:25 ` [PATCH v9 3/8] mm: Move set/get_pcppage_migratetype to mmzone.h Alexander Duyck
2019-09-09 8:22 ` David Hildenbrand
2019-09-09 9:56 ` Kirill A. Shutemov
2019-09-09 18:01 ` Alexander Duyck
2019-09-09 18:12 ` Alexander Duyck
2019-09-10 12:23 ` Michal Hocko
2019-09-10 14:46 ` Alexander Duyck
2019-09-10 17:45 ` Michal Hocko
2019-09-10 20:26 ` Alexander Duyck
2019-09-07 17:25 ` [PATCH v9 4/8] mm: Use zone and order instead of free area in free_list manipulators Alexander Duyck
2019-09-10 12:27 ` Michal Hocko
2019-09-07 17:25 ` [PATCH v9 5/8] arm64: Move hugetlb related definitions out of pgtable.h to page-defs.h Alexander Duyck
2019-09-09 8:52 ` David Hildenbrand
2019-09-09 15:27 ` Alexander Duyck
2019-09-17 17:48 ` Will Deacon
2019-09-17 20:07 ` Alexander Duyck
2019-09-07 17:25 ` [PATCH v9 6/8] mm: Introduce Reported pages Alexander Duyck
2019-09-09 14:42 ` Kirill A. Shutemov
2019-09-09 16:25 ` Alexander Duyck
2019-09-09 16:33 ` Kirill A. Shutemov
2019-09-07 17:26 ` [PATCH v9 7/8] virtio-balloon: Pull page poisoning config out of free page hinting Alexander Duyck
2019-09-09 8:59 ` David Hildenbrand
2019-09-09 15:31 ` Alexander Duyck
2019-09-07 17:26 ` [PATCH v9 8/8] virtio-balloon: Add support for providing unused page reports to host Alexander Duyck
2019-09-07 17:34 ` [PATCH v9 0/8] mm / virtio: Provide support for unused page reporting Alexander Duyck
2019-09-10 12:42 ` [PATCH v9 0/8] stg mail -e --version=v9 \ Michal Hocko
2019-09-10 14:42 ` Alexander Duyck
2019-09-10 14:47 ` Michal Hocko [this message]
2019-09-10 16:05 ` Alexander Duyck
2019-09-10 16:18 ` [virtio-dev] " Dr. David Alan Gilbert
2019-09-10 16:22 ` David Hildenbrand
2019-09-11 9:23 ` Michael S. Tsirkin
2019-09-11 9:50 ` David Hildenbrand
2019-09-10 17:52 ` Michal Hocko
2019-09-10 18:00 ` Michal Hocko
2019-09-10 20:37 ` Alexander Duyck
2019-09-10 21:23 ` Alexander Duyck
2019-09-11 11:36 ` Michal Hocko
2019-09-11 11:47 ` David Hildenbrand
2019-09-11 12:08 ` Michael S. Tsirkin
2019-09-11 12:19 ` Michal Hocko
2019-09-11 12:25 ` Michal Hocko
2019-09-11 12:42 ` David Hildenbrand
2019-09-11 12:54 ` Michal Hocko
2019-09-11 13:03 ` David Hildenbrand
2019-09-11 13:20 ` Michal Hocko
2019-09-11 13:51 ` Michal Hocko
2019-09-11 16:09 ` David Hildenbrand
2019-09-12 7:16 ` Michal Hocko
2019-09-12 7:47 ` David Hildenbrand
2019-09-12 9:26 ` Michal Hocko
2019-09-12 12:00 ` Nitesh Narayan Lal
2019-09-11 14:03 ` Nitesh Narayan Lal
2019-09-11 16:02 ` David Hildenbrand
2019-09-11 13:19 ` Nitesh Narayan Lal
2019-09-11 12:55 ` Nitesh Narayan Lal
2019-09-11 15:12 ` Alexander Duyck
2019-09-12 9:19 ` Michal Hocko
2019-09-12 10:24 ` Kirill A. Shutemov
2019-09-12 11:11 ` Michal Hocko
2019-09-12 15:42 ` Alexander Duyck
2019-09-12 16:35 ` Mel Gorman
2019-09-12 17:48 ` Alexander Duyck
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=20190910144713.GF2063@dhcp22.suse.cz \
--to=mhocko@kernel.org \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=alexander.duyck@gmail.com \
--cc=alexander.h.duyck@linux.intel.com \
--cc=catalin.marinas@arm.com \
--cc=dan.j.williams@intel.com \
--cc=dave.hansen@intel.com \
--cc=david@redhat.com \
--cc=fengguang.wu@intel.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=konrad.wilk@oracle.com \
--cc=kvm@vger.kernel.org \
--cc=lcapitulino@redhat.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mst@redhat.com \
--cc=nitesh@redhat.com \
--cc=osalvador@suse.de \
--cc=pagupta@redhat.com \
--cc=pbonzini@redhat.com \
--cc=riel@surriel.com \
--cc=virtio-dev@lists.oasis-open.org \
--cc=wei.w.wang@intel.com \
--cc=will@kernel.org \
--cc=willy@infradead.org \
--cc=yang.zhang.wz@gmail.com \
--cc=ying.huang@intel.com \
/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).