Re: [Qemu-devel] [PATCH 00/12][RFC] char: add flow control and fix guest_[open|close]

[Alon Levy]

On Mon, Aug 01, 2011 at 09:22:58AM -0500, Anthony Liguori wrote:
> The char layer has been growing some nasty warts for some time now as we ask 
> it
> to do things it was never intended on doing.  It's been long over due for an
> overhaul and its become evident to me that we need to address this first 
> before
> adding any more features to the char layer.
> 
> This series is the start at sanitizing the char layer.  It effectively turns
> the char layer into an internal pipe.  It supports flow control using an
> intermediate ring queue for each direction.
> 
> This series is an RFC because I don't think we should merge the series until 
> we
> completely convert the old style flow control users to the new style.
> 
> One particularly nasty area is the mux device.  I'm not entirely sure yet how
> to preceed there.
> 
> 

So, adding a copy - is that really a good idea? I don't have any alternative 
code,
so I'm already starting bad, I know, and I understand the want to have a "middle
ground" to ease the logic. Maybe keeping an iovec? add a function on each side 
for
freeing, i.e. release_be_buffer, release_fe_buffer. At least it could make this 
as
fast as the current code. I'm thinking of copy/paste for vdagent, usbredir, 
guest
agent doing dmesg or anything larger.