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Re: [PATCH v1 2/3] io: Add zerocopy and errqueue
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH v1 2/3] io: Add zerocopy and errqueue |
Date: |
Wed, 8 Sep 2021 09:30:58 +0100 |
User-agent: |
Mutt/2.0.7 (2021-05-04) |
* 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
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, (continued)
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, Leonardo Bras Soares Passos, 2021/09/02
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, Leonardo Bras Soares Passos, 2021/09/02
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, Daniel P . Berrangé, 2021/09/02
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, Leonardo Bras Soares Passos, 2021/09/02
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, Daniel P . Berrangé, 2021/09/02
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, Leonardo Bras Soares Passos, 2021/09/02
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, Daniel P . Berrangé, 2021/09/02
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, Dr. David Alan Gilbert, 2021/09/07
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, Peter Xu, 2021/09/07
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue,
Dr. David Alan Gilbert <=
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, Peter Xu, 2021/09/08
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, Dr. David Alan Gilbert, 2021/09/09
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, Leonardo Bras Soares Passos, 2021/09/08
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, Peter Xu, 2021/09/08
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, Daniel P . Berrangé, 2021/09/08
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, Peter Xu, 2021/09/08
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, Leonardo Bras Soares Passos, 2021/09/09
- Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, Peter Xu, 2021/09/09
Re: [PATCH v1 2/3] io: Add zerocopy and errqueue, Leonardo Bras Soares Passos, 2021/09/02