[Linrad] Re: Priority and IP addresses

[Joe Taylor <Princeton.EDU; joe@xxxxxxxxxxxxxxxx>]

Hi Leif and all,

It's very likely that you or others on this reflector know a great deal 
more about this than I do.

Some relevant facts I've determined empirically by running Linrad 
together with MAP65 include the following:

1. On the three Windows machines I've tested, if both Linrad and 
MAP65-IQ are run on the same machine it is necessary to run Linrad at 
"Above Normal" priority.

2. There is no need (and I think no incentive) to run MAP65 at an 
elevated priority.  MAP65 is not a real-time program in the same sense 
that Linrad is; it has no tight tolerances to maintain in order to avoid 
  glitches in audio output, etc.  When running in Windows, the MAP65 
process sets itself to NORMAL_PRIORITY_CLASS.  The two threads that 
handle UDP packet input (from Linrad) and audio output (to the SSB 
transmitter) are set to THREAD_PRIORITY_ABOVE_NORMAL; the thread that 
does decoding is set to THREAD_PRIORITY_BELOW_NORMAL.

3. With this setup, Windows is still perfectly usable for email, web 
browsing, compiling programs, etc., while Linrad and MAP65 continue to 
run without problems.

4. MAP65-IQ can be configured to "listen" on IP address 127.0.0.1 while 
Linrad (running on the same machine, call it computer A) sends timf2 
packets to either 127.0.0.1 or the machine's own IP address (e.g., 
172.16.28.32).  No changes are required to MAP65-IQ for both addresses 
to work in Linrad.  I took it that this means the "localhost" address 
127.0.0.1 is little more than a placeholder for the real IP address.

5. If Linrad runs on computer B, and MAP65 or MAP65-IQ on computer A, 
Linrad should send its timf2 data explicitly to the IP address of 
computer A.  Computer A can still "listen" on 127.0.0.1, however.

Perhaps there would be a difference in CPU loading if I had MAP65 listen 
on its own IP address instead of 127.0.0.1.  I have made no tests to try 
to determine this.  Unless it is true (at a level that really matters 
when receiving timf2 data sampled at about 96 kHz, I can see no 
advantage to making MAP65's input IP address anything other than 
127.0.0.1.  Have I missed something important?

	-- 73, Joe, K1JT

Leif Asbrink wrote:
> Hi All,
> 
> I have changed the setup in Linrad-03.03 to allow priorities 0 to 3.
> 0=normal
> 1=above normal
> 2=high
> 3=realtime
> 
> When I run Linrad with soundcards on various systems I see no
> problems, generally higher priority is better because I can
> then run other applications without interruptions in Linrad.
> 
> When running with USB input it is different. Setting realtime
> priority for Linrad degrades the USB performance and makes
> the maximum sampling rate something like 140 kHz for SDR-IQ
> while 183 kHz is ok at priority high and below.
> 
> I can run Linrad with timf2 output on the network at 95238 kHz
> for MAP65-IQ without any problems at all priority levels
> when using the default ip address 239.255.0.0.
> 
> BUT when I change to 127.0.0.1 it is different. When sending
> to this address, the maximum priority allowed is above normal.
> 
> I think it would be a very good idea to change MAP65-IQ (and MAP65?)
> to receive data on its own address. The reason I made 239.255.0.x the
> default in Linrad is that I found somewhere that this is the address
> range where the systems expect UDP packages. (Of course) I do not
> know whether that makes the system behave differently for different
> IP address ranges. But systems know UDP packages may get lost.....
> 
> I think it would be nice to set MAP65-IQ in priority above normal
> while setting Linrad in priority high. Then it should be possible
> to run various other programs simultaneously without adverse effects.
> Today it is NOT possible because the use of 127.0.0.1 makes the
> highest usable priority above normal for Linrad and then MAP65-IQ
> would have to be run at normal priority.
> 
>    73
> 
>   Leif / SM5BSZ

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