busy wait problem, see original message below
we are on top of it, as of may 10...
again vinay, please pay my (due) respects to matt, do say that it is NOT a
full busy wait (I.e. n-1 threads go to sleep) but one thread ALWAYS goes
through and therefore under high load it can become a problem...
I will try to fix this this week as simone is visiting napa valley and 17
miles drives (btw he is a VERY nice guy)...
marcf
|-----Original Message-----
|From: Bordet, Simone [mailto:[EMAIL PROTECTED]]
|Sent: Thursday, May 10, 2001 5:59 PM
|To: 'marc fleury'
|Subject: R: Busy wait on one thread
|
|
|Hi Marc,
|
|> Simone,
|>
|> ok the semaphore stuff lets' one go through but you release
|> the semaphore
|> before you do the execution of the code. Therefore we lock
|> the instance and
|> then release the semaphore mutex and the next thread comes in.
|>
|> If you have 2 threads, one comes in passes the mutex,
|> acquires the ctx lock
|> and releases the mutex. It then goes on to execute an update
|> that takes,
|> for example, one minute.
|>
|> The second thread comes in, passes the mutex (no one is
|> there), try to get
|> the ctx lock but sees it is locked and just goes on logging
|> "LOCKING-WAITING" and TRIES AGAIN.
|>
|> This gives rise to tons of LW messages with 2 threads
|>
|> This is a busy wait for one thread, you do not sync on the
|> state of the
|> target context since your release is just on the mutex.
|>
|> Unless I am missing something, we need to rethink this a bit.
|> I will make
|> the time to fix it
|
|Correct.
|I already had heavy sessions on it say one month ago, but did not finished,
|and then got damn busy at work.
|FYI, I changed the busy wait to a wait-notify (I already commited the
|utility class WaitSemaphore under jboss/util for that, but not the
|interceptor), then run into troubles with the instance pool and the
|transactions (commit C), finally I thought "I should debug one thing at a
|time", and eventually run out of time. I'm a bit upset for this, I'd really
|like to spend much more time on JBoss...
|After June I should have more time, at work the pressure should lighten.
|Anyway I'm open to help anyone wants to take a cranck on that code, or fix
|it myself when I'll have more time, just let me know.
|Oh, I will spend 3 weeks (summer holidays) in US after JavaOne,
|maybe we can
|keep in touch and have a beer together, why not ?
|
|Regards,
|
|Simon
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