Hi, I've just spend the last 1.5 days tracking down some weird latency issues which were showing up when testing spice usb-redir over a network connection (rather then over loopback).
I managed to trace it to a simple read() call on the socket for the (unencrypted) usb-redir channel taking up to 7 ms. Since this is done from qemu's iothread, this blocks amongst other things the ehci controller emulations timer from running for that amount, while it should run every ms. At first I thought the issue was because the socket was maybe not set to non-blocking. But in the end it turns out to be a kernel issue, one of the debugging options enabled in Fedora-18's / rawhides kernels causes these latencies. I've already verified that this is not an issue introduced in the 3.6 kernel versus the stable 3.5 kernel F-17 has, when ever a new rc gets released one build is done in koji without the debugging options, ie: http://koji.fedoraproject.org/koji/buildinfo?buildID=354745 These builds work fine, only the builds with the debugging options show these huge increases in latencies under certain circumstances. Regards, Hans p.s. The above is all just FYI, I don't expect anyone to do something about this, I just wanted others to be aware of this issue, so that they don't end up chasing ghosts like I did. _______________________________________________ Spice-devel mailing list Spice-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/spice-devel
