From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sasha Levin <levinsasha928@gmail.com>
Subject: Re: [PATCH 5/5] ioeventfd: Introduce KVM_IOEVENTFD_FLAG_SOCKET
Date: Thu, 14 Jul 2011 11:07:14 +0300
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Cc: Avi Kivity <avi@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>,
	kvm@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
	Marcelo Tosatti <mtosatti@redhat.com>
To: Pekka Enberg <penberg@kernel.org>
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On Thu, 2011-07-14 at 10:26 +0300, Pekka Enberg wrote:
> On 07/13/2011 04:00 PM, Pekka Enberg wrote:
> >> On Wed, Jul 13, 2011 at 3:57 PM, Avi Kivity<avi@redhat.com>  wrote:
> >> >>  We'd like to keep 8250 emulation because it's the most robust method
> >> >>  for getting data out of the kernel when there's problems. It's also
> >> >>  compatible with earlyprintk and such.
> >> >
> >> >  What do you hope to gain from the optimization? 100ms less boot time?
> >>
> >> Hmm? I use serial console for logging into the guest and actually
> >> using it all the time.
> 
> On 7/13/11 4:32 PM, Avi Kivity wrote:
> > Just how fast do you type?
> >
> > It's not enough to make something faster, it has to be slow to being 
> > with.  The interface is good, but use it where it helps.
> 
> I don't know why you bring up serial console input here. Sasha's
> original KVM_IOEVENTFD_FLAG_PIPE patch clearly stated:
> 
>    A simple example for practical use is the serial port. we are not
>    interested in an exit every time a char is written to the port, but
>    we do need to know what was written so we could handle it on the
>    guest.
> 
> So it's talking about the serial console output, not input.

Yes, I have originally thought of doing the pipefd interface to prevent
the overhead caused by console intensive benchmarks on actual
benchmarks. It's funny how much slowness spinning the cursor or printing
a table incurs.

-- 

Sasha.