On Thu, Oct 13, 2005 at 09:24:35AM -0500, LRK wrote: > On Thu, Oct 13, 2005 at 12:35:50AM -0700, Eric Blossom wrote: > > > > > > I believe it was gnuradio-examples/python/usrp/benchmark_usb.py that > > > triggered the problem here. > > > > That should be the right answer, but is not completely reliable. > > Since I don't have a Tx board, I couldn't run that test "as is". It > tries to open the Tx board first. I'll do a little hacking on something > and then see if I encounter the problem doing something similar with > two Rx boards or opening the Rx board first. > > > > Try running test_usrp_standard_rx with different values of the > > -D <decim> option. Start with -D 128, then try -D 64, -D 32, -D 16, -D 8. > > > > -D 128 500kS/sec 2MB/sec > > -D 64 1MS/sec 4MB/sec > > -D 32 2MS/sec 8MB/sec > > -D 16 4MS/sec 16MB/sec > > -D 8 8MS/sec 32MB/sec > > These tests show the apparent 4MB/s limit which Wulf has mentioned. There > also seem to be something that is related to the 4MB points in the actual > transfers. I have run tests with 3.9 MB transfers with no overruns and > 4.0 MB transfers with exactly 1. I would also expect the noverruns to go up > as -D goes down. > > Clues there. Just don't know what they mean yet.
Don't use the -M option with small values. You won't get a good answer unless you let it run for 10 - 20 seconds or so. We want to know what it will sustain over an extended period of time. You'll probabably want to run each test a couple of times too. [There may be a problem where the fifo's aren't flushed between runs which is another reason to use longer test periods. I think that may be why usb_benchmark doesn't work as expected.] > ./test_usrp_standard_rx -M 16 -D 128 > xfered 1.68e+07 bytes in 8.4 seconds. 1.998e+06 bytes/sec. cpu time = 0.1549 > noverruns = 1 > ./test_usrp_standard_rx -M 16 -D 64 > xfered 1.68e+07 bytes in 4.19 seconds. 4e+06 bytes/sec. cpu time = 0.1501 > noverruns = 0 > ./test_usrp_standard_rx -M 16 -D 32 > xfered 1.68e+07 bytes in 4.11 seconds. 4.078e+06 bytes/sec. cpu time = 0.152 > noverruns = 20 > ./test_usrp_standard_rx -M 16 -D 16 > xfered 1.68e+07 bytes in 4.1 seconds. 4.094e+06 bytes/sec. cpu time = 0.155 > noverruns = 10 > ./test_usrp_standard_rx -M 16 -D 8 > xfered 1.68e+07 bytes in 4.1 seconds. 4.095e+06 bytes/sec. cpu time = 0.1483 > noverruns = 5 Looks like you get something on the order of 4MB/sec. Not surprising given that it's not pipelining the requests. If you've got a logic analyzer available and want to play, I can give you some suggestions of things to watch. I suspect that what you'll see are *highly* variable inter-packet arrival times. > > Likewise, try test_usrp_standard_tx with different values of the > > -I <interp> option. Start with -I 256, then try -I 128, 64, 32, 16. > > Can't, no Tx board. The measurement should work fine with no Tx board. Eric _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
