Re: [Qemu-devel] [PATCH 2/4] vnc: allow the Buffer to shrink again

[Peter Lieven]

Am 03.09.2015 um 13:52 schrieb Gerd Hoffmann:
>    Hi,
>
> > > Beside that I think it makes sense to have the shrinking logic in
> > > buffer_reserve too so we don't have to add buffer_shrink calls all over
> > > the place.
> > We need a possibility to shrink the buffer after it has been used.
> > Especially the queue->buffer.
> That works fine.  Test patch attached.

Not completely. queue->buffer may remain big, if you disconnect in the
wrong moment. Maybe there should be a buffer_free if the last client
disconnects?

In general I like your modified patch because the shrinking is slower than
in my version. for 64*1024 you should introduce a macro.

> I'm not sure this is the way to go though.  I see alot of growing and
> shrinking.  We also do alot of coping (each realloc, but also from
> buffer to buffer).
>
> We might be better off redoing the whole buffer management, at least
> once we are done with encoding one frame.  Passing on a *pointer* to the
> buffer, once sent to the wire just free the buffer.  Allocate a new one
> for the next frame.  That way we copy around less data and also don't
> have to worry about big unused buffers in the first place ...

Maybe this should be the permanent solution.

Peter