[omniORB] Latencies - Oneway vs. Roundtrip

[Alberto Squassabia]

It may not be omniORB that does the buffering.  Some TCP implementations
(don't know exactly about NT, though) are optimized for throughput, not
latency, and don't put a socket buffer on the wire until the buffer is
full.

[Re: [omniORB] Latencies - Oneway vs. Roundtrip] Helge.Penne@datarespons.=
no
wrote:
>
> Jim Redman wrote:
>
> > I have a counter-intuitive latency problem and would like some input =
and
> > validation of what I think I'm seeing.  This is strictly latency, not
> > throughput.   Running between two NT 4.0 system with 2.7.0 I see late=
ncies
> > for oneway messages that appear to approach 100ms.  When I change the=
 same
> > calls to roundtrip the latencies drop below the NT measurable time (a=
bout
> > 10ms?).
> >
> > Has anyone seen anything similar or different, that is, can anyone co=
nfirm
> > or deny my numbers.
>
> I'm doing some benchmarking at this very moment, and just discovered th=
is
> latency myself.  The test uses a "publish/subscribe" pattern to distrib=
ute a
> packet of data from a server to a client application.  I ran both progr=
ams on
> the same NT 4.0 computer with a packet rate of 100Hz, and saw latencies=
 of up
> to 200ms when using oneway calls.  With ordinary calls, the latency is =
hardly
> ever measurable using GetTickCount.
>
> What was really revealing was that the latency would start at approx. 4=
0ms,
> and then increase by 10ms for each call until it would reach 200 ms.  I=
t
would
> then fall back to 40ms and start over.
>
> My theory is that omniORB buffers my oneway calls and sends them in lar=
ger
> packages every 200ms (5Hz).  This explains every symptom that I have se=
en,
and
> also fits in nicely with my previous experience with VisiBroker.  VisiB=
roker
> also buffers such requests by default, but there is an option in BOA_in=
it
that
> lets you turn off this buffering and force these requests to be sent
> immediately.
>
> This leads up to a very important question: How do we turn off this buf=
fering
> in omniORB?  This is quite an important question for my project.  Has a=
nybody
> done this before?
>
> --
> Helge Penne (helge.penne@datarespons.no)
> Senior Software Development Engineer
> Data Respons AS, Postboks 489, N-1323 H=F8vik, Norway
> Phone: +47 67112081 / 22719957 (work/home)
>
>
>
>>>-- End of excerpt from Helge.Penne@datarespons.no -----------------<<<



--
Alberto Squassabia  (970)898-7705  alsq@cnd.hp.com  HP TMD
"   We are Pentium of Borg. Division is futile. You      "
"   will be approximated. (ca. AD 1995)                  "