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Re: [Discuss-gnuradio] Confusing uO Errors

From: Nick Foster
Subject: Re: [Discuss-gnuradio] Confusing uO Errors
Date: Wed, 05 Jan 2011 10:28:29 -0800

You're probably getting interrupted by some scheduler-chewing task. If
you don't mind risking locking your system up, try prefacing your
command with "sudo nice -n-20 " to give your process priority.

You should also benchmark your HDD with hdparm or Bonnie to get a handle
on what you can actually write for sustained periods of time.

If all else fails, create a ramdisk to save your samples:

mount -t tmpfs /mnt/ramdisk -o -size=512m

...and copy them over to HDD when you're done streaming.


On Wed, 2011-01-05 at 10:47 -0500, Neil Bedwell wrote:
> Hello,
> I am having overruns that I cannot get figured out, and I am on a time
> crunch to get this resolved.  Any help would be appreciated.
> Problem:
> I seem to get uO's that appear irregularly, maybe every 20 seconds or so on
> average.
> Script in Python: 
> USRP with 2 TVRx boards -> Decimation set to 64 (1MHz BW, also tried 128,
> with same result) -> Split Stream -> Store samples as two interleaved I/Q
> files (4MB/s per file)
> That data is what I expect out, so I don't suspect that the Python code is
> incorrect
> Computer:
> Core2 Duo >2GHz per core (runs at 1GHz while executing)
> Ubuntu 10.04 fresh install on Ext4 hard drive (Also tried 10.10, and have
> tried AHCI settings to both On and Compatibility in BIOS)
> USB benchmark succeeds at 32MB/s (8MB/s should not be an issue)
> Latest GNU Radio from git (also tried 3.3.0)
> High-speed hard drive, more than capable of 8MB/s writes (HD light only
> flashes every few seconds when script is running)
> I have tried playing with fusb_block_size/nblocks, but don't know a good
> configuration to set, and haven't had luck reducing the uO's
> Questions:
> What else can I try?
> Are there buffer sizes that I can increase on the computer so that there is
> room during the hard drive block writes?
> Thanks,
> Neil
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