On Wed, 14 Mar 2012 10:01:15 +0000 Stefan Hajnoczi <stefa...@gmail.com> wrote:
> On Wed, Mar 14, 2012 at 9:51 AM, Gerd Hoffmann <kra...@redhat.com> wrote: > > Hi, > > > >> The most practical first step would be simply sending the ppm over a > >> socket from ppm_save(). The 'screendump' command today already blocks > >> so no new badness is being added. There would be no threads or fancy > >> image encoding. > > > > Adding scaling / compression support will add more overhead though, so > > doing that without offloading screendump to a thread first is a bad idea > > I think. Or at least have some numbers to see how bad it actually is. > > I agree, that's why I suggest sending the ppm over a socket. It > transports out the image data and QEMU itself doesn't do the > encoding/scaling. Just out of curiosity, are we planning to extend the current screendump command or add a new one? If we just extend the current command, then we'll have to make the "filename" parameter optional. But this is a compatible change, I think. Also, when returning the image via fd, we could offload its writing to a bh. This would give us a poor man's async support, where the biggest drawback would the lack of error detection (can this operation fail anyway?).
