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Date: Thu, 21 Mar 2013 19:46:35 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
Message-ID: <20130321174635.GA4112@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v3 9/9] coalesce adjacent iovecs
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To: Juan Quintela <quintela@redhat.com>
Cc: Orit Wasserman <owasserm@redhat.com>, chegu_vinod@hp.com, qemu-devel@nongnu.org, pbonzini@redhat.com

On Thu, Mar 21, 2013 at 06:44:14PM +0100, Juan Quintela wrote:
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
> > On Thu, Mar 21, 2013 at 06:27:42PM +0200, Orit Wasserman wrote:
> >> On 03/21/2013 06:16 PM, Michael S. Tsirkin wrote:
> >> > On Thu, Mar 21, 2013 at 06:05:40PM +0200, Orit Wasserman wrote:
> >> >> This way we send one big buffer instead of many small ones
> >> >>
> >> >> Signed-off-by: Orit Wasserman <owasserm@redhat.com>
> >> > 
> >> > Why does this happen BTW?
> >> 
> >> It happens in the last phase when we send the device state that
> >> consists of a lot
> >> bytes and int field that are written using qemu_put_byte/be16/...
> >> 
> >
> > Confused  I thought device_state does not use _nocopy?
> > My idea of using vmsplice relies exactly on this:
> > we can not splice device state ...
> 
> 
> As it is today, I am not sure that we can use vmsplice() because we
> are sending:
> 
> 
> <header>
> <page>
> <header>
> <page>
> <header>
> <page>
> 
> We can optimize at some pount to write a bigger/different header and
> sent a bunch of pages together, but just now we don't have that code.
> 
> Later, Juan.

Sending the page can do vmsplice, can't it?
Multipage is likely a good idea anyway, e.g. RDMA wants to
do this too.