When the deferred update timer behavior was recently overhauled such that it pushes out updates whenever the timer is triggered rather than waiting for an update request from the client, the default DUT value was also changed to 10 ms (from 1 ms.) Unfortunately, setting the DUT to 10 ms results in a dramatic decrease in peak performance on high-speed networks. The reason is that, when the timer is set, all X updates that arrive between that time and the time it is triggered are "coalesced." As soon as the timer is triggered, a framebuffer update containing all of the coalesced X updates is sent immediately, then the server is tied up sending the update and cannot process any new X updates until the update is sent. Once the update is sent, then the first new X update starts the deferred update timer again. Effectively, what this means is that the frame rate is capped to 1 / (deferred update time + encoding time), and since the encoding time is typically about 20 ms for a 1280x1024 screen, setting the DUT to 10 ms caps the frame rate at about 30 Hz for such a screen, whereas previously it was near 50 Hz when the DUT was 1 ms.
I'm not sure how best to address this, but it does represent a performance regression, since LAN performance has now decreased by 40% with default settings. DRC ------------------------------------------------------------------------------ All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-novd2d _______________________________________________ Tigervnc-devel mailing list Tigervnc-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/tigervnc-devel
