From: Peter Xu <peterx@redhat.com>
To: "Daniel P. Berrangé" <berrange@redhat.com>
Cc: "Elena Ufimtseva" <elena.ufimtseva@oracle.com>,
"John G Johnson" <john.g.johnson@oracle.com>,
"Jagannathan Raman" <jag.raman@oracle.com>,
qemu-block@nongnu.org, "Juan Quintela" <quintela@redhat.com>,
"Dr. David Alan Gilbert" <dgilbert@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>
Subject: Re: [PATCH v1 2/3] io: Add zerocopy and errqueue
Date: Wed, 8 Sep 2021 22:05:39 -0400 [thread overview]
Message-ID: <YTlr8xIFOFym2cFy@xz-m1.local> (raw)
In-Reply-To: <YTkrHUMMV0xDmHCU@redhat.com>
On Wed, Sep 08, 2021 at 10:57:06PM +0100, Daniel P. Berrangé wrote:
> We think we're probably ok with migration as we are going to rely on the
> face that we eventually pause the guest to stop page changes during the
> final switchover. None the less I really strongly dislike the idea of
> not honouring the kernel API contract, despite the potential performance
> benefits it brings.
Yes understandable, and it does looks tricky. But it's guest page and it's just
by nature how it works to me (sending page happening in parallel with page
being modified).
I think the MSG_ZEROCOPY doc page mentioned that and it's userspace program's
own choice if that happens. So even if it's not by design and not suggested, it
seems not forbidden either.
We can wr-protect the page (using things like userfaultfd-wp) during sending
and unprotect them when it's done with a qio callback, that'll guarantee the
buffer not changing during sending, however we gain nothing besides the "api
cleaness" then..
Thanks,
--
Peter Xu
next prev parent reply other threads:[~2021-09-09 2:06 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
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 [this message]
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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