On Mon, 26 Jan 2004, Steve Watt wrote: > [EMAIL PROTECTED] wrote: > >do what ping does (ping -f) > >when you get an ENOBUFS do a usleep for 1 mSec. > >and then send it again. > > So how, exactly, do you actually sleep for 1mSec? I recently did some > experiments using nanosleep(), and it seems that the minimum sleep time > is 2 / HZ. I.e. ask for 100nS, get 20mS (on a 10mS-ticking system). > > Mind you, that behavior is precisely aligned with what POSIX says should > happen, since nanosleep() is not allowed to return success before the > specified amount of time has expired, and you might be calling it 5nS > before the clock tick. But it does make doing correct Tx pacing a bit > more challenging.
For what it's worth, when I tried this I wound up using gettimeofday (IIRC) as a "macroscopic" clock and calculating nanosecond sleeps between transmits; drift due to HZ was correctable because I knew the average throughput I was after. -- jan grant, ILRT, University of Bristol. http://www.ilrt.bris.ac.uk/ Tel +44(0)117 9287088 Fax +44 (0)117 9287112 http://ioctl.org/jan/ That which does not kill us goes straight to our thighs. _______________________________________________ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"
