RE: [Discuss-gnuradio] Unexplained out-of-sequence packets...

[Ian Holland]

Hi Eric

I was not running through a switch.

I tried what you suggested, and can confirm that the CPUs are not being
throttled. I have then discovered that for some reason I can only get
the problem to occur on one of my two host PCs. I am trying to install
the new Ubuntu (actually, the 64-bit version thereof) for the time
being, after formatting the hard drive, and am hoping it will work on
this PC afterwards.

Cheers

Ian.
 

-----Original Message-----
From: Eric Blossom [mailto:address@hidden 
Sent: Thursday, 13 May 2010 4:07 AM
To: Ian Holland
Cc: address@hidden
Subject: Re: [Discuss-gnuradio] Unexplained out-of-sequence packets...

On Wed, May 12, 2010 at 04:34:36PM +0930, Ian Holland wrote:
> Hi Eric
> 
> It seems this has not fixed the problem. Does anyone have any other
> suggestions as to the possible cause? Note, I also found power cycling
> the USRP2 can sometimes avoid the same problem.
> 
> Ian.

Ian,

I still suspect something in your host setup.

Is the USRP2 connected directly to the host or does it go through a
switch?  If there's a switch in the path, please remove it.

Note that the cpu throttling / clock scaling hypothesis would explain
why it works better under higher load than lower load.  Are you sure
that your cpu isn't being throttled?

When you're seeing the problem, try:

  $ grep 'cpu MHz' /proc/cpuinfo

and see if all cores are running at full speed.

E.g.,

Idling laptop (throttled back from 1.83GHz):

  address@hidden ~]$ grep 'cpu MHz' /proc/cpuinfo
  cpu MHz               : 1000.000
  cpu MHz               : 1000.000


Server with cpu scaling disabled:

  address@hidden swig]$ grep 'cpu MHz' /proc/cpuinfo
  cpu MHz               : 2999.488
  cpu MHz               : 2999.488
  cpu MHz               : 2999.488
  cpu MHz               : 2999.488
  cpu MHz               : 2999.488
  cpu MHz               : 2999.488
  cpu MHz               : 2999.488
  cpu MHz               : 2999.488

Eric


> -----Original Message-----
> From: address@hidden
> [mailto:address@hidden
On
> Behalf Of Ian Holland
> Sent: Tuesday, 11 May 2010 11:14 AM
> To: Eric Blossom
> Cc: address@hidden
> Subject: RE: [Discuss-gnuradio] Unexplained out-of-sequence packets...
> 
> Thanks Eric
> 
> I checked the power management preferences and couldn't see anything
> about CPU throttling, though I did verify it would never go to sleep
> after inactivity. Then, I found some info on
>
http://blog.mpathirage.com/2009/10/04/how-to-disable-dynamic-frequency-s
> calingcpu-throttling-in-ubuntu-jaunty9-04/ to disable the CPU
throttling
> (I know I am using 9.10, not 9.04, but I imagine it should be the
same).
> 
> After rebooting (only once), I haven't yet seen the problem again.
> Unfortunately, given the seemingly random nature of the problem, I
guess
> it is a wait-and-see matter as to whether it ever does resurface.
> 
> Cheers
> 
> Ian.