FW: Re: Linrad, ps aux numbers, etc(Leif Åsbrink Sept 15 2002)

[Leif Åsbrink <leif.asbrink@xxxxxxxxxxxxxxxxxxxx]

-----Original Message-----
From: owner-linrad@xxxxxxxxxxxxxxx
[mailto:owner-linrad@xxxxxxxxxxxxxxx]On Behalf Of Leif Åsbrink
Sent: Sunday, September 15, 2002 6:12 PM
To: Linrad
Subject: [linrad] Re: Linrad, ps aux numbers, etc


Hi All,

Roger, W3SZ wrote:
 
> If you look at the bottom left of the Linrad screen, Leif has provided a
> '%time' readout.  Leif notes that this parameter indicates "% of the
> time available for processing within the dsp program".  On my system
> running with a 96000 Hz sampling rate and a 90+ KHz wide waterfall, with
> very aggressive parameters, this % time is (while sampling one of the
> famous FRH files) 28.3%.  It is a good index of what happens to
> processor load as you change parameters.
> 
> If you use 'ps aux' or 'ps ux' etc you will get vastly different numbers
> than this, as you have discovered.  When I run 'ps aux' or 'ps ux' or
> whatever from another terminal, the Linrad numbers generally run at 98
> or 99% for %cpu.  This is with a pentium 4 running at 1.4 GHZ.

To this I like to add:
  
When you run ps aux or something else you should ideally get 100%
cpu use. The Linrad program uses all cpu time available to it.

If you get 90% only, some other process is also using cpu time leaving
less to Linrad. You may start other processes and watch how the Linrad
internal %-meter goes up while the ps aux percentage for Linrad goes down.

The reason is I do not know how to tell the Linux kernel that my program
actually does not need the cpu for a while:-)

What happens is that Linrad is in a loop doing nothing. It calls the
output device occasionally to find out if there is space available
for a new block of output data. If data is coming from the A/D converter
it also checks if a new block of input data is yet available (when reading
from disk the program knows input data is always there)

73

Leif  /  SM5BSZ






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