Hello
I have been doing some stress and performance tests on James 2.3.1 and I
think I have found a bottleneck on the James spool storing code (I am using
the filesystem spool).
I have configured James to behave as a simple SMTPServer and do almost
nothing more than receiving mails and storing it in the spool ("<mailet
match="All" class="Null"/>"). When stressing James (sending 10 messages per
second) I see higher and higher times on the mail handle time, with times of
5, 6 and even 10 seconds instead of the 100 ms. average time that I got when
James is not stressed out. I am measuring these times on the SMTP client, so
these are times from the start of the SMTP session to the end of it (in
James this correspond with the time until the mail is store in the spool, if
I am not mistaken) and not include the mail processing time.
After some digging I found that James was spending all the time on the
File_Persistent_Stream_Repository.put method. All the input threads spend
most of the time (almost 99%) waiting to enter in that method, because it is
synchronized. I do not understand why this method it is synchronized: it
does not access to any shared resources or anything. Any explanation?
Just for testing, I remove the synchronized from that method and several
others (i.e. File_Persistent_Object_Repository.put). I get a very little
performance boost but not very much because in that case the
FileOutputStream object created inside the
File_Persistent_Stream_Repository.put method start taking a lot of time.
So, summarizing:
1. Why the File_Persistent_*_Repository methods are synchronized?
2. Anyone knows why the FileOutputStream object creation takes more and more
when James is stress out? The underlying OS is not reporting any problems
with the filesystem or the file descriptors.
Any ideas will be more than welcome. This bottleneck is really hurting our
performance. We can afford to have some poor performance after the spool but
not before it.
Details:
- Solaris 8
- JDK 6.0u12 (500M RAM heap)
- Sun-Fire-V240 (1 CPU)
- Input throughput: 10 message per second
- James config:
----- SmtpServer.connectionTimeout = 30000
----- StmpServer.connectionLimit = 150
----- thread-group.max-threads = 200
- Input threads busy with 10 messages per second ---> around 60 threads
regards and thanks in advance (and sorry for the long long post ;) ),
Rafael Munoz
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