distributed performance test

Serge Aleynikov <>
Mon Apr 25 02:17:40 CEST 2005


Thanks Matthias,

I'd like to also confirm that I am not getting this weird behavior on 
other computers, yet this particular machine (devlinuxpro2) is quite 
powerful: 4CPUs, 4G RAM, 100M Eithernet, 100% idle, and I am not certain 
on how to interpret this result.

This time I am showing results of three tests:
1. A client and a server are on different nodes running on the same host 
(Linux).

2. A client and a server are on different nodes running on different 
hosts (both have Linux).

3. A client and a server are on different nodes running on different 
hosts with less powerful hardware (a Windows PC and a Linux server)

Test# CLIENT          SERVER          #ofClients Calls/sec Ping(us)
===== ======          ======          ========== ========= ========
1a      1          5714
1b      5	         3067

2a       1          1727      150us/0% loss
2b       5	         54        <---- !!!!

2c       1          4115      150us/0% loss
2d       5	         50        <---- !!!!

3a           1          842       400us/0% loss
3b           5	         603

and just for the sake of simmetry:

2e           1          582      400us/0% loss
2f           5	  16       <---- !!!!

So, what are the reasonable questions to ask at this point about 
devlinuxpro2?

Since two nodes running on the same host don't express this problem, it 
must be due to a mulfinctioning network interface.  On the other hand, 
why in that case, I don't see any problem when running a single client? 
  So, assuming that something _is_ wrong with the network interface, how 
can such a problem be troubleshot (tcpdump dosn't show anything 
suspicious either)?

Ideally, I'd like to be able to see some stats from the message passing 
layer in Erlang in order to determine the speed of packets of interest 
arriving to the node, but before they are dispatched to the process' 
mailbox.  This way, I would know that the delay is in fact external to 
Erlang.  Is there a way to get that?

Thanks.

Serge


Matthias Lang wrote:

> Ignore my previous post... The source was included in another message.
> 
> I re-ran your tests on two machines and I do _not_ see the unexpected
> behaviour you're seeing. You reported:
> 
>  > CLIENT          SERVER          THREADS PERFORMANCE (Calls/sec)
>  > ======          ======          ======= =======================
>  > 		1	238095
>  > 		5	43478
>  > 
>  > 	 1	2364
>  > 	 5	71        !!!  Why?
> 
> Repeating this on a PC and a laptop:
> 
> CLIENT          SERVER          THREADS PERFORMANCE (Calls/sec)
> ======          ======          ======= =======================
>             1       257997
>             5        52714
> 
>            1         1193
>            5          319
> 
>            1          905
>            5          340
> 
> The machines were "mostly idle" when I ran the tests. I used R9C on
> both. The network between them is slow (10Mbit, hub). Ping roundtrip
> time is about 400us.
> 
> Matthias
> 
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