> Frediano Ziglio писал 2020-06-23 18:01: > > > Frediano Ziglio писал 2020-05-25 10:19: > > > > > > > > I have a problem with slow rendering of a changing desktop via a slow > > > > > > > > > > > > > > > network. SPICE tries to render all the states of the screen > > > > > > > > > > > > > > > sequentially, instead of immediately drawing the final state. > > > > > > > > > >
> > > > > What settings can you remove this behavior? > > > > > > > > > > > > > > Hi, > > > > > > > > > > I'm not sure, unfortunately, there's a way to entirely remove this > > > > > > > > > > behavior, > > > > > > > > > > at least with current optimizations. > > > > > > > > > > Can you describe better your case? > > > > > > > > > > What's slow mean, I mean, speed? 10Mbit? Less? More? > > > > > > > > > > Do you know the latency of the connection? > > > > > > > > > > What type (mobile/wifi/cabled/lan/wan) ? > > > > > > > > > > Which kind of guest (OS/configuration/use case) are you using? > > > > > > > > > > In the subject you state a "slow network" in the message you speak > > > > > > > > > > about "slow rendering", that's quite different from the way I see it, > > > > > > > > > > what specific issues are you noting? > > > > > > > > > > Frediano > > > > > > > > > The channel is UDP OpenVPN via the Internet. The total load from > > > > > > everything turns out to be about 100Kib. But this is not a direct > > > > > > channel limitation. The channel may be larger. If you use the TCP > > > > > > version of OpenVPN, then it will be displayed even more slowly. It seems > > > > > > that the server is waiting for some confirmation from the client. > > > > > > Client and server Ubuntu 18.04. > > > > > > With a smooth fading or brightening of the Windows screen on a virtual > > > > > > machine on the client, I see all the successively changing brightness. > > > > > > The same thing happens when a video or something changes is drawn in the > > > > > > browser. > > > > > Hi, > > > not much to recommend with these conditions. I think quite out of SPICE > > > can handle. > > > The original design was more about sending rendering commands to clients > > > which does not help much with so slow bandwidth. > > > One of the 2 options to try is to force "wan optimization" setting it to > > > "always". This will use more JPEG for compression. Another would be to > > > reduce "jpeg_quality" setting (dcc.cpp) to a lower value (currently fixed > > > to 85). > > > An unfortunately VPN and queueing does not help, especially if TCP. > > > The reason is that while the server (which mainly send data) has a fast > > > connection to the VPN gateway the client doesn't so the server probably > > > will use a large queue causing latency issues. I have a quite dirty and > > > experimental patch to limit the queue but it won't help with other issues. > > > I think (it could be I'm wrong) that an approach more VNC like (drawing > > > all at host/guest level then send the collapsed changes to client) would > > > be better. I have another dirty patch but at the moment is even worse > > > at the optimization level so won't help too. > > > Regards, > > > Frediano > > Indeed, the VSC works better under such conditions. But unfortunately it > doesn’t have some very convenient functions, for example, auto-adjustment of > the server size for the client. > As I understand from your letter, sending data for rendering occurs through > the queue. As an idea, I can offer to combine packages for rendering if they > have not had time to leave yet. Or monitor the queue overflow and, in case > of overflow, clear it and send the entire screen in one packet. This will > give the desired effect for channels with minimal performance. Hi, I was more speaking at queue in general, but I think part of the issue are the network buffers in this case beside client queue. I prepare a small experimental branch at https://gitlab.freedesktop.org/fziglio/spice/-/tree/wan_experiments if you want to try, it allows to define SPICE_DEBUG_SNDBUF and SPICE_DEBUG_JPEG_QUALITY (see https://gitlab.freedesktop.org/fziglio/spice/-/commit/2d3939a424284e44203bd5ed25cd37dbb9e66623 and https://gitlab.freedesktop.org/fziglio/spice/-/commit/ba64ca4ef02ee2aa49401f199aebff6ef6f93d63 ), they should help a bit. I tried to limit my network to 100KB/s and it was less terrible than I though, beside an initial pretty large time to start. Regards, Frediano
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