Long wait interval between requests with a single threaded client
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Key: DIRMINA-221
URL: http://issues.apache.org/jira/browse/DIRMINA-221
Project: Directory MINA
Type: Improvement
Reporter: Emmanuel Lecharny
Priority: Critical
Hi MINA band,
we are currently experiencing a very strange behavior in MINA. While doing
performances tests of ADS? we found that we cannot go upper than 25 search
requests per second. We stripped the server from its backend, and eventually,
Alex wrote a single client/server program unsing MINA to isolate the pb.
Vasically, we have a client which continuously send requests, and get a result
from a very simplified server. If the client has only one thread running, there
is a wall we hit ate around 25 req/s. If we use more than one thread, suddenly
this wall go up to NbThreads*25 req/s (ie, with 4 threads requesting, we reach
100 req/s, with 10, 250 req/s, ... with 100 threads, we have 1500 req/s).
After having put some traces into MINA, here what I found in BlockingQueue :
those two methods seems to be connected. When you call notifyAdd, then the
method waitForNewItem() wait stops. We are waiting for an average of 40ms for
each request in the waitForNewItem() method, ad I don't know which kind of
processing or synchronization generate those 40ms wait.
...
private void notifyAdded()
{
if( waiters > 0 )
notify();
}
...
...
public synchronized void waitForNewItem() throws InterruptedException
{
waiters++;
try
{
while( super.isEmpty() )
{
wait();
...
Here is a sample of time wait we have in the fetchBuffer() method, which call
the waitForNewItem() method (time is in ms) :
...
Waited : 42
fetchBuffer : 42
Waited : 0
fetchBuffer : 0
Waited : 1
fetchBuffer : 1
Waited : 39
fetchBuffer : 39
Waited : 0
fetchBuffer : 0
Waited : 1
fetchBuffer : 1
Waited : 39
fetchBuffer : 39
Waited : 0
fetchBuffer : 0
Waited : 1
fetchBuffer : 1
Waited : 39
fetchBuffer : 39
Waited : 0
fetchBuffer : 0
Waited : 1
...
I know that the wait I get the delay is not very optimal
(System.currentTimeMillis()), but 40 ms is *very* long.
At this point, Alex and me are clueless. We have not enough understanding on
the Mina internals to explian and fix this problem - if it's a problem -, or to
configure MINA to avoid this kind of behavior.
If any of you could help us, this will be *very* appreciated, as the whole LDAP
server perfomance relies on MINA.
Thanks !
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