From: Anthony Liguori <anthony@codemonkey.ws>
To: Uri Lublin <uri@il.qumranet.com>
Cc: Avi Kivity <avi@redhat.com>, kvm@vger.kernel.org
Subject: Re: [PATCH] qemu: qemu_fopen_fd: differentiate between reader and writer user
Date: Thu, 16 Oct 2008 21:47:35 -0500 [thread overview]
Message-ID: <48F7FCC7.2020108@codemonkey.ws> (raw)
In-Reply-To: <48F75483.1020901@il.qumranet.com>
Uri Lublin wrote:
>
> That is true, but in the case I mentioned above it would take the
> management tool some time (guest down time) to realize what happens,
> and to send "cont" to the SRC. With end-of-migration messages SRC
> discovers DST fails and immediately continues.
> I agree those messages add some complexity, and slow things a bit for
> the good/average case.
It's the classic general's dilemma. If SRC waits for DST to send an
ACK, DST still doesn't know whether SRC received the ACK so it doesn't
know whether it's truly safe to continue.
This is why migration doesn't quit SRC immediately, and leaves SRC in
the stopped state. It's because the only safe way to handle this is
with a third party that is reliable.
Regards,
Anthony Liguori
next prev parent reply other threads:[~2008-10-17 2:47 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-10-12 16:30 [PATCH] qemu: qemu_fopen_fd: differentiate between reader and writer user Uri Lublin
2008-10-12 16:55 ` Avi Kivity
2008-10-12 18:09 ` Anthony Liguori
2008-10-12 18:17 ` Avi Kivity
2008-10-12 22:18 ` Anthony Liguori
2008-10-13 3:03 ` Anthony Liguori
2008-10-16 1:36 ` Uri Lublin
2008-10-16 4:14 ` Anthony Liguori
2008-10-16 8:13 ` Avi Kivity
2008-10-16 12:54 ` Anthony Liguori
2008-10-16 14:23 ` Uri Lublin
2008-10-16 14:32 ` Avi Kivity
2008-10-16 14:49 ` Uri Lublin
2008-10-17 2:47 ` Anthony Liguori [this message]
2008-10-19 13:46 ` Uri Lublin
2008-10-19 22:00 ` Anthony Liguori
2008-10-22 16:23 ` Uri Lublin
2008-10-16 10:52 ` Uri Lublin
2008-10-16 0:13 ` Uri Lublin
2008-10-16 4:10 ` Anthony Liguori
2008-10-16 8:16 ` Avi Kivity
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=48F7FCC7.2020108@codemonkey.ws \
--to=anthony@codemonkey.ws \
--cc=avi@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=uri@il.qumranet.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.