From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
To: Peter Xu <peterx@redhat.com>
Cc: "Elena Ufimtseva" <elena.ufimtseva@oracle.com>,
"John G Johnson" <john.g.johnson@oracle.com>,
"Daniel P. Berrangé" <berrange@redhat.com>,
qemu-block@nongnu.org, "Juan Quintela" <quintela@redhat.com>,
qemu-devel <qemu-devel@nongnu.org>,
"Leonardo Bras Soares Passos" <leobras@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Marc-André Lureau" <marcandre.lureau@redhat.com>,
"Fam Zheng" <fam@euphon.net>,
"Jagannathan Raman" <jag.raman@oracle.com>
Subject: Re: [PATCH v1 2/3] io: Add zerocopy and errqueue
Date: Wed, 8 Sep 2021 09:30:58 +0100 [thread overview]
Message-ID: <YTh0wn1IoaJpVwQ9@work-vm> (raw)
In-Reply-To: <YTeq1jttqpuVC3ZD@t490s>
* Peter Xu (peterx@redhat.com) wrote:
> On Tue, Sep 07, 2021 at 12:06:15PM +0100, Dr. David Alan Gilbert wrote:
> > > > What if we do the 'flush()' before we start post-copy, instead of after each
> > > > iteration? would that be enough?
> > >
> > > Possibly, yes. This really need David G's input since he understands
> > > the code in way more detail than me.
> >
> > Hmm I'm not entirely sure why we have the sync after each iteration;
>
> We don't have that yet, do we?
I think multifd does; I think it calls multifd_send_sync_main sometimes,
which I *think* corresponds to iterations.
Dave
> > the case I can think of is if we're doing async sending, we could have
> > two versions of the same page in flight (one from each iteration) -
> > you'd want those to get there in the right order.
>
> From MSG_ZEROCOPY document:
>
> For protocols that acknowledge data in-order, like TCP, each
> notification can be squashed into the previous one, so that no more
> than one notification is outstanding at any one point.
>
> Ordered delivery is the common case, but not guaranteed. Notifications
> may arrive out of order on retransmission and socket teardown.
>
> So no matter whether we have a flush() per iteration before, it seems we may
> want one when zero copy enabled?
>
> Thanks,
>
> --
> Peter Xu
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
next prev parent reply other threads:[~2021-09-08 8:36 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-31 11:02 [PATCH v1 0/3] QIOChannel flags + multifd zerocopy Leonardo Bras
2021-08-31 11:02 ` [PATCH v1 1/3] io: Enable write flags for QIOChannel Leonardo Bras
2021-09-01 20:54 ` Eric Blake
2021-09-02 8:26 ` Leonardo Bras Soares Passos
2021-08-31 11:02 ` [PATCH v1 2/3] io: Add zerocopy and errqueue Leonardo Bras
2021-08-31 12:57 ` Daniel P. Berrangé
2021-08-31 20:27 ` Peter Xu
2021-09-01 8:50 ` Daniel P. Berrangé
2021-09-01 15:52 ` Peter Xu
2021-09-01 15:59 ` Daniel P. Berrangé
2021-09-02 7:07 ` Leonardo Bras Soares Passos
2021-09-02 6:59 ` Leonardo Bras Soares Passos
2021-09-07 16:44 ` Peter Xu
2021-09-08 20:13 ` Leonardo Bras Soares Passos
2021-09-08 21:04 ` Peter Xu
2021-09-02 6:38 ` Leonardo Bras Soares Passos
2021-09-02 8:47 ` Daniel P. Berrangé
2021-09-02 9:34 ` Leonardo Bras Soares Passos
2021-09-02 9:49 ` Daniel P. Berrangé
2021-09-02 10:19 ` Leonardo Bras Soares Passos
2021-09-02 10:28 ` Daniel P. Berrangé
2021-09-07 11:06 ` Dr. David Alan Gilbert
2021-09-07 18:09 ` Peter Xu
2021-09-08 8:30 ` Dr. David Alan Gilbert [this message]
2021-09-08 15:24 ` Peter Xu
2021-09-09 8:49 ` Dr. David Alan Gilbert
2021-09-08 20:25 ` Leonardo Bras Soares Passos
2021-09-08 21:09 ` Peter Xu
2021-09-08 21:57 ` Daniel P. Berrangé
2021-09-09 2:05 ` Peter Xu
2021-09-09 4:58 ` Leonardo Bras Soares Passos
2021-09-09 16:40 ` Peter Xu
2021-08-31 11:02 ` [PATCH v1 3/3] migration: multifd: Enable zerocopy Leonardo Bras
2021-08-31 13:16 ` Daniel P. Berrangé
2021-08-31 20:29 ` Peter Xu
2021-09-01 8:53 ` Daniel P. Berrangé
2021-09-01 15:35 ` Peter Xu
2021-09-01 15:44 ` Daniel P. Berrangé
2021-09-01 16:01 ` Peter Xu
2021-09-02 7:57 ` Leonardo Bras Soares Passos
2021-09-07 11:13 ` Dr. David Alan Gilbert
2021-09-08 15:26 ` Daniel P. Berrangé
2021-09-02 7:23 ` Jason Wang
2021-09-02 8:08 ` Leonardo Bras Soares Passos
2021-09-02 7:27 ` Leonardo Bras Soares Passos
2021-09-02 7:22 ` Leonardo Bras Soares Passos
2021-09-02 8:20 ` Daniel P. Berrangé
2021-09-02 8:52 ` Leonardo Bras Soares Passos
2021-09-02 9:20 ` Daniel P. Berrangé
2021-09-02 9:49 ` Leonardo Bras Soares Passos
2021-09-02 9:59 ` Daniel P. Berrangé
2021-09-02 10:25 ` Leonardo Bras Soares Passos
2021-09-07 11:17 ` Dr. David Alan Gilbert
2021-09-07 18:32 ` Peter Xu
2021-09-08 2:59 ` Jason Wang
2021-09-08 3:24 ` Peter Xu
2021-09-08 3:26 ` Jason Wang
2021-09-08 8:19 ` Dr. David Alan Gilbert
2021-09-08 15:19 ` Peter Xu
2021-09-09 1:10 ` Jason Wang
2021-08-31 21:24 ` [PATCH v1 0/3] QIOChannel flags + multifd zerocopy Peter Xu
2021-09-01 19:21 ` Leonardo Bras Soares Passos
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