On 10/21/2010 02:10 AM, Eric Blossom wrote: > On Thu, Oct 21, 2010 at 12:41:16AM -0400, Marcus D. Leech wrote: > >> I had a flow-graph that earlier today had a latency of roughly 1 second >> or so. >> >> When I tested it this evening, after it had been running for several >> hours, the latency was >> back up to *several tens of seconds*!!!. Which means that external >> events at the source take >> several tens of seconds to show up at the sinks -- two graphical, and >> one filesink. WTF? !! >> >> The CPU load at the time was modest -- about 38% >> > 38% of what? How many cores? What kind of machine? > A dual-core machine, an Atom D-510 > It's possible that there's a computation in a single block that > requires > 1 core to compute in realtime. > Unlikely. The most "computey" block is a 1024-bin FFT, and my sample rate is only 400Ksps. There's also an FFT filter, but it typically has only about 40-45 taps.
> Have you tried oprofile to see where the graph is spending its time? > Are you i/o bound? What's the rate that you're writing to the file sink? > I'm writing to the file sink at 1Ksps. There's also an audio sink, I'm using the "plughw:0,0" device, and it's being pumped at 20Ksps, which generally divides my source rate exactly. I tried turning off that sub-tree the other night, but I didn't let it run very long. Perhaps a residual clock-rate mis-match is causing 'buffer creep', and after a few hours, that 'buffer creep' has grown to several-10s of seconds? > I believe htop will show you all the threads of the process. Are any > of them consuming on the order of 100% of a single core? > > Eric > > Hmm, have to check that. OK, just installed 'htop' and there's no single thread that's chewing on near 100% of a cpu. The top two threads peak at around 70% and 30%, but average somewhat less than that. -- Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
