Peter Crowther wrote:
From: David kerber [mailto:dcker...@verizon.net]
Now that I've got a thread dump, what am I looking for?
You found it first time :-). Now the hard part - fixing it.
Yeah, that's what I figured!
I've got a
bunch of sections like this, pretty much all of which are waiting to
lock <0x057c73e0>. Is there any way to figure out what that
object is?
I imagine it's the disk write, but can't figure out how to
tell for sure.
It's the sync at the start of your method.
[2009-05-08 10:43:24] [info] waiting for monitor entry
[2009-05-08 10:43:24] [info] [0x2739f000..0x2739fb64]
[2009-05-08 10:43:24] [info] at
eddsrv.EddRcvr.doPost(EddRcvr.java:70)
[2009-05-08 10:43:24] [info] - waiting to lock <0x057c73e0> (a
eddsrv.EddRcvr)
I also have quite a few blocks like this:
[2009-05-08 10:43:23] [info] "http-1024-Processor10"
[2009-05-08 10:43:23] [info] daemon
[2009-05-08 10:43:23] [info] prio=6 tid=0x271f1418
[2009-05-08 10:43:23] [info] nid=0xa74
[2009-05-08 10:43:23] [info] in Object.wait()
[2009-05-08 10:43:23] [info] [0x275df000..0x275dfae4]
[2009-05-08 10:43:23] [info] at java.lang.Object.wait(Native Method)
[2009-05-08 10:43:23] [info] at java.lang.Object.wait(Unknown Source)
[2009-05-08 10:43:23] [info] at
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:656)
[2009-05-08 10:43:23] [info] - locked <0x0510e6e0> (a
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable)
[2009-05-08 10:43:23] [info] at java.lang.Thread.run(Unknown Source)
[2009-05-08 10:43:23] [info]
I assume these are just threads waiting for something to do (waiting for
a request)?
... so they're all waiting to get the monitor on a eddsrv.EddRcvr, which is what the
"synchronized" on your doPost method will lock on.
Until you said that, I didn't even notice that I had what appear to be
"double" synchronizations, making the method synchronized, and also
having synchronized{} blocks inside it. I assume I've been
double-screwing myself all this time??
protected synchronized void doPost(HttpServletRequest request,
HttpServletResponse response )
throws ServletException, IOException {
synchronized ( criticalProcess ) {
totalReqCount++;
dailyReqCount++;
processRequest( request, response, false );
}
}
If you say pretty much all are stuck there, then you have massive contention on
that monitor. Time to move to some finer-grained locking! As a first step,
I'd remove the synchronized from the method; I'd replace it with one lock
around the counter updates (locked on one object) and another lock in your
decrypt/log/respond code that's purely around the logging section (locked on a
different object). Then I'd re-evaluate - run, take another thread dump and
see where the bottlenecks are now. If they're anywhere, I'll bet they're
around the logging code.
Thanks!
D
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