[concurrency-interest] Low cpu usage with fair ReentrantLock

Andrew Haley aph at redhat.com
Tue May 11 04:31:25 EDT 2010


On 05/10/2010 11:42 PM, David Holmes wrote:
> Andrew Haley writes on Tuesday, 11 May 2010 2:36 AM:
>> Perhaps so.  It's hard to tell from that javadoc exactly what is
>> meant: I thought, from reading that, that "slower; often much slower"
>> referred to slow operation with high CPU loads when locking rather
>> than, as we have here, CPUs being starved of work.  But in any case,
>> given the fact that locking is so rare, I found this result a little
>> bit surprising.
> 
> Just one further comment. Locking may be "rare" from the perspective of
> locked-work:unlocked-work, but it would seem that your threads are executing
> in-phase, and so contention is actually high.

So it seems.  They don't start in phase, but because of the convoying
effect they eventually move into lock-step.  I wonder how often this
happens  the real world applications.

Andrew.



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