Hi, I think the key sysctl here is this one: kern.ipc.maxsockbuf=8000000 which determines the max UDP buffer sizes (the others, as Chris points out, are only relevant to TCP).
What would be useful to check is to run netstat -s on your system with and without the ker.ipc.maxsocketbuf setting - and look at the UDP section on "dropped due to full socket buffers" and see how this changes. However this is odd as vic does set the socket buffer sizes in the application. One explanation maybe that the application provided buffer sizes are a guide and if they're overrun then it can use more memory but if the default max (on my MacBook they're set to 262144) is too low then they will run out and hence you'll get bad video. The other thing that is strange is that this doesn't appear to happen on Linux (maybe it is and we haven't noticed it) but after a quick look at the Linux kernel it seems that the SO_RCVBUF setsocketopt() kernel implementation doubles the supplied value which may makes things ok on Linux? However the max buffer size in Linux (Ubuntu 7.10 anyway) is /proc/sys/net/core/wmem_max 131071 (which is lower than OSX)... If we find that vic's default's are too low then we can tweak them, though it may only be fixed on some systems but increasing the system maximum..... It maybe worth keeping an eye on UDP buffer overruns (use netstat -s) to see if this a more general problem. There's a good guide on UDP buffer sizing here: http://www.29west.com/docs/THPM/udp-buffer-sizing.html Piers. On 10/11/2007, gurcharan khanna <[email protected]> wrote: > Christoph Willing wrote: > > > > On 10/11/2007, at 7:56 AM, gurcharan khanna wrote: > > > >> Mark, > >> > >> my link to the source for this seems to be broken but here's what i > >> have personally on my mac. > >> > >> in /etc/sysctl.conf, add these lines: > >> > >> > >> net.inet.tcp.recvspace=4000000 > >> net.inet.tcp.sendspace=4000000 > >> kern.ipc.maxsockbuf=8000000 > > > > > > Those settings look like they may have come from: > > http://www.psc.edu/networking/projects/tcptune/ > You're right about the URL. However, the link doesn't work anymore.... > > > > However, note that TCP tuning is the subject there, not UDP (which is > > what multicast uses). > Understood. However, changing these settings DOES in fact improve things > considerably, predictably, > and repeatedly. I don't quite understand it, but it does work. > > -gurcharan > > > > > > chris > > > > > > > >> you probably have to restart to activate them. you can set these from > >> the command line as well but they won't "stick", but you can try out > >> different > >> settings that way. > >> > >> use: sysctl -w net.inet.tcp.recvspace=4000000 (for example) > >> > >> to set these values interactively. > >> > >> -gurcharan > >> > >> > >> > >> Leonard, Mark wrote: > >>> Listers-- > >>> > >>> It was probably a year ago that a setting change for Mac OS that > >>> improved video quality of big video multicast streams (Gurcharan?) > >>> but I > >>> can't seem to find it any where... > >>> > >>> Can someone repost or point me towards a troubleshooting page for > >>> tweaks > >>> like this? > >>> > >>> Thanks > >>> Mark > >>> > >>> > >>> Mark Leonard > >>> DL Studios, UNH > >>> 603-862-0192 > >>> > >>> > >>> > >>> > >>> > >> > >> -- > >> ------------------------- > >> Gurcharan S. Khanna, Ph.D. > >> Director of Research Computing > >> Office of the Vice President for Research > >> > >> Director, Interactive Collaboration Environments Laboratory, > >> Center for the Advancing the Study of Cyberinfrastructure > >> --- > >> Rochester Institute of Technology > >> 1 Lomb Memorial Drive > >> Rochester, New York 14623-5603 > >> Phone: 585-475-7504 ~ Cell: 585-451-8370 > >> Email: [email protected] > >> Http: people.rit.edu/gskpop > >> > > > > Christoph Willing +61 7 3365 8350 > > QCIF Access Grid Manager > > University of Queensland > > > > > > > > > -- > ------------------------- > Gurcharan S. Khanna, Ph.D. > Director of Research Computing > Office of the Vice President for Research > > Director, Interactive Collaboration Environments Laboratory, > Center for the Advancing the Study of Cyberinfrastructure > --- > Rochester Institute of Technology > 1 Lomb Memorial Drive > Rochester, New York 14623-5603 > Phone: 585-475-7504 ~ Cell: 585-451-8370 > Email: [email protected] > Http: www.rit.edu/~gskpop > >
