Re: [Vacm-general] Slow EMP handling

['Ard v. Breemen' <ar...@te...>]

On Wed, Jul 25, 2001 at 04:28:45PM +0200, 'Ard van Breemen' wrote:
> On Wed, Jul 25, 2001 at 03:21:29PM +0200, 'Ard van Breemen' wrote:
> > On Tue, Jul 24, 2001 at 11:26:11AM -0700, San Mehat wrote:
> > > As I suspected, it looks like you're having a serial protocol issue..
> > > The reason that only the cisco boxes are qualified as a *network* based
> > > connectivity method for EMP are that they have below 1 ms round trip
> > > latency on single byte transactions on their raw ports... The EMP
> > > protocol requires a MAXIMUM latency of 2ms per byte.. otherwise it will
> > > timeout the byte (and sometimes the fame). It is VERY difficult to
> > But how is the byte acked? What happens with modems? If I hook up a
> > modem, the round trip will probably exceed that 2 ms due to compression
> > and other stuff. We are after all talking about almost 4 byte-times.
> Allright...
> Debugging using tcpdump and ethereal.
> My system send a byte to the portmaster.
> 1.37 ms later the portmaster acks.
> 53 ms later the portmasters sends a packet containing data.
> Usually 1 byte as a reaction from my system. But sometimes up to 29 bytes.
> But always 53 ms...
> As if something was nagging... Or at least some timer seems to be involved...
It get's worse:
Enabled all emp debugging (like DEBUG_TRANS),
the download still takes long, but other actions are currently fast.
Refresh of the node will fail the first time. As if it tries to reconnect
with a connection still open.  The second time it works (maybe the
connection is closed due to the failure of opening it :) ).

Anyway:
ard@c24574:/net/home/ard$ time vash -c localhost -u blum -p frub -x 'ipc localhost emp:chassis_status:rs0'
EMP:124:JOB_STARTED
EMP:124:CSTATUS:YES:NO:NO:NO:NO:YES:NO:NO:NO:NO:NO:YES:NO:NO:NO
EMP:124:JOB_COMPLETED

real    0m0.818s
user    0m0.000s
sys     0m0.000s
ard@c24574:/net/home/ard$ time vash -c localhost -u blum -p frub -x 'ipc localhost emp:chassis_status:rs0'
EMP:127:JOB_STARTED
EMP:127:CSTATUS:YES:NO:NO:NO:NO:YES:NO:NO:NO:NO:NO:YES:NO:NO:NO
EMP:127:JOB_COMPLETED

real    0m0.528s
user    0m0.000s
sys     0m0.000s

The .5 s is median. It either takes .5 s or .8 s.

The download_log takes about the same time, but that is probably cached?
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