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Date: Mon, 26 Mar 2007 22:52:57 +0200
From: Emmanuel Lecharny <elecharny@gmail.com>
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To: Apache Directory Developers List <dev@directory.apache.org>
CC: matt@hogstrom.org
Subject: Benchmarks feedback
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Hi,

I have done some benchmarks on the powerfull server on which Matt was 
kind enough to give me an access (8 dual core CPUs, 11 131 mogomips, 20 
Gb mem !).

The results are pretty preliminary, and a little bit disappointing. Here 
are the tests I did :

- 4 clients requesting the server;
- each client doing 10 000 random requests for each run;
- 12 runs for each client with a fixed number of thread;
- a number of thread being 1, 2, 4, 5, 8, 10, 20 and 50.

the best result I reached was around 1600 req/s, CPU peaked to 300 % 
(which means that no more than 3 cpus out of 16 where used), a maximum 
of 20% total CPU out of which 2,5% system. Not exactly brillant.

I would have excpected that the CPU would have been more working more, 
so I guess something is wrong (contention, or not enough threads, or 
threads not being distributed enough, or simply not enough clients ).

The last point (not enough client) should not be the reason : with only 
one client, I almost reached the same level of performance, and each new 
client added does not make a lot of difference (maybe 10% more requests 
being fulfilled ...)

I don't think either that threads are not correctly distributed on the 
CPUs, because I tried with Sun JVM and Jrockit, and I get similar 
results, always above 250% (which means that threads are really 
distributed). However, I have no idea on how to know which CPU is a 
thread running on (any clue ?)

So, contention. I did some other tests :
1) always requesting the same entry
2) requesting the rootDSE only

Both tests should be running without any disk access (any idea on how to 
get some info about disk access, btw ?). Here are the results (same 
clients, same number of requests
1) same entry : around 4500 req/s, which is 3 times the number with 
random searches. CPU peaked to 400%, no more...
2) rootDSE : 11500 req/s. Same CPU peak.

I have one more test to run, I want to setup a higher cache size, to see 
if it has some impact on the first scenario results.

Ok, I will really appreciates any idea, any suggestion, any information 
whcih can help to find out why we are so limited.

Thanks a lot for the server, Matt, this is really helpfull ! You will 
deserve a bunch of beers in may :) (let's say one beer for eacj thousand 
requests per second we can get :)

Emmanuel