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From Knut Anders Hatlen <Knut.Hat...@Sun.COM>
Subject Re: Releasing latches when waiting for locks. When and why?
Date Wed, 22 Nov 2006 13:18:14 GMT
Daniel John Debrunner <djd@apache.org> writes:

> Knut Anders Hatlen wrote:
>> Mike Matrigali <mikem_app@sbcglobal.net> writes:
>>
>>> Having said that it would be interesting if someone had time to
>>> implement a higher performance latch implementation and plug it in
>>> and see how much it helps.  It would decrease the total time spent
>>> in lock manager.
>>
>> Ok, a new experiment: I removed the calls to LockFactory.latchObject()
>> and LockFactory.unlatch() in BasePage. Instead, I let BasePage check
>> manually whether it was latched and use wait/notifyAll if it was. The
>> patch (which is very simple) is attached.
>>
>
> The original decision to use the lock manager for the latches was to
> enable easier debugging of deadlocks during the early development of
> the store code. A local latch implementation, like Knut Anders made,
> does make a lot of sense, but does leave derby open to undetectable
> deadlocks. Given the performance gains it probably is worth the risk,
> especially since I don't think we've seen a problem with latch
> ordering for many years.

Thanks to you all for your input! I have logged DERBY-2107 and will
start working on a local latch implementation along the lines of the
patch I sent out.

-- 
Knut Anders

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