From: Tyler Sanderson <tysand@google.com>
To: "Wang, Wei W" <wei.w.wang@intel.com>
Cc: David Hildenbrand <david@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
Nadav Amit <namit@vmware.com>,
Alexander Duyck <alexander.h.duyck@linux.intel.com>,
"virtualization@lists.linux-foundation.org"
<virtualization@lists.linux-foundation.org>,
David Rientjes <rientjes@google.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Michal Hocko <mhocko@kernel.org>
Subject: Re: Balloon pressuring page cache
Date: Wed, 5 Feb 2020 10:43:04 -0800 [thread overview]
Message-ID: <CAJuQAmrVLV_XDKLoGoRL7Ep8=xj0oio6VE9_3cRhE5s0eZY2sw@mail.gmail.com> (raw)
In-Reply-To: <286AC319A985734F985F78AFA26841F73E41F367@shsmsx102.ccr.corp.intel.com>
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On Wed, Feb 5, 2020 at 1:00 AM Wang, Wei W <wei.w.wang@intel.com> wrote:
> On Wednesday, February 5, 2020 4:57 PM, David Hildenbrand wrote:
> > >> Yes, I agree with you. Yet, I am thinking about one
> > >> (unlikely?impossible?) scenario. Can you refresh my brain why that
> > >> cannot happen (IOW, why we don't have to wait for the host to process
> > >> the request)?
> > >>
> > >> 1. Guest allocates a page and sends it to the host.
> > >> 2. Shrinker gets active and releases that page again.
> > >> 3. Some user in the guest allocates and modifies that page. After
> > >> that, it is done using that page for the next hour.
> > >> 4. The host processes the request and clears the bit in the dirty
> bitmap.
> > >> 5. The guest is being migrated by the host. The modified page is not
> > >> being migrated.
> > >
> > > Whenever the guest modifies a page during migration, it will be
> > > captured by the dirty logging and the hypervisor will send the dirtied
> the
> > page in the following round.
> >
> > Please explain why the steps I outlined don't apply esp. in the last
> round.
> > Your general statement does not explain why this race can't happen.
> >
>
> The guest is stopped in the last round, thus no page will be modified at
> that time.
>
Isn't the hint only useful during the *first* round?
After the first round if a page becomes free then we need to update the
copy at the migration destination, so freeing a page that previously had
contents should mark it dirty.
>
> Best,
> Wei
>
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next prev parent reply other threads:[~2020-02-05 18:43 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAJuQAmpDUyve2S+oxp9tLUhuRcnddXnNztC5PmYOOCpY6c68xg@mail.gmail.com>
[not found] ` <91270a68-ff48-88b0-219c-69801f0c252f@redhat.com>
[not found] ` <CAJuQAmoaK0Swytu2Os_SQRfG5_LqiCPaDa9yatatm9MtfncNTQ@mail.gmail.com>
2020-01-30 15:02 ` David Hildenbrand
2020-01-30 15:20 ` Michael S. Tsirkin
2020-01-30 15:23 ` David Hildenbrand
2020-01-30 15:31 ` Wang, Wei W
2020-01-30 19:59 ` Tyler Sanderson
2020-02-03 13:11 ` Michael S. Tsirkin
2020-02-03 16:18 ` Alexander Duyck
2020-02-03 16:34 ` David Hildenbrand
2020-02-03 17:03 ` Michael S. Tsirkin
2020-02-03 20:32 ` Tyler Sanderson
2020-02-03 21:22 ` Alexander Duyck
2020-02-03 23:16 ` Tyler Sanderson
2020-02-04 0:10 ` Alexander Duyck
2020-02-04 5:45 ` Michael S. Tsirkin
2020-02-04 8:29 ` David Hildenbrand
2020-02-04 18:52 ` Tyler Sanderson
2020-02-04 18:56 ` Michael S. Tsirkin
2020-02-04 19:17 ` David Hildenbrand
2020-02-04 23:58 ` Tyler Sanderson
2020-02-05 0:15 ` Tyler Sanderson
2020-02-05 6:57 ` Michael S. Tsirkin
2020-02-05 19:01 ` Tyler Sanderson
2020-02-05 19:22 ` Alexander Duyck
2020-02-05 21:44 ` Tyler Sanderson
2020-02-06 11:00 ` David Hildenbrand
2020-02-03 22:50 ` Nadav Amit
2020-02-04 8:35 ` David Hildenbrand
2020-02-04 8:40 ` Michael S. Tsirkin
2020-02-04 8:48 ` David Hildenbrand
2020-02-04 14:30 ` David Hildenbrand
2020-02-04 16:50 ` Michael S. Tsirkin
2020-02-04 16:56 ` David Hildenbrand
2020-02-04 20:33 ` Michael S. Tsirkin
2020-02-05 8:31 ` David Hildenbrand
2020-02-05 6:52 ` Wang, Wei W
2020-02-05 7:05 ` Michael S. Tsirkin
2020-02-05 8:50 ` Wang, Wei W
2020-02-05 6:49 ` Wang, Wei W
2020-02-05 8:19 ` David Hildenbrand
2020-02-05 8:54 ` Wang, Wei W
2020-02-05 8:56 ` David Hildenbrand
2020-02-05 9:00 ` Wang, Wei W
2020-02-05 9:05 ` David Hildenbrand
2020-02-05 9:19 ` Wang, Wei W
2020-02-05 9:22 ` David Hildenbrand
2020-02-05 9:35 ` Wang, Wei W
2020-02-05 9:37 ` David Hildenbrand
2020-02-05 9:49 ` Wang, Wei W
2020-02-05 9:58 ` David Hildenbrand
2020-02-05 10:25 ` Michael S. Tsirkin
2020-02-05 10:42 ` David Hildenbrand
2020-02-05 9:35 ` Michael S. Tsirkin
2020-02-05 18:43 ` Tyler Sanderson [this message]
2020-02-06 9:30 ` Wang, Wei W
2020-02-05 7:35 ` Nadav Amit
2020-02-05 8:19 ` David Hildenbrand
2020-02-05 10:27 ` Michael S. Tsirkin
2020-02-05 10:43 ` David Hildenbrand
2020-01-30 22:46 ` Tyler Sanderson
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