Re: performance analysis producer_consumer.cc TEST_T5

[Felix Yen <fwy at alumni dot brown dot edu>]

[Loren, sorry for the duplicate.  -- fwy]

>  I'm not the author of that sequence of tests but it looks OK to me
>  (although it has a quirk that makes the actual workload of the
>  producer-consumer path non-deterministic...).

If you're referring to the fact that the result depends on how the 
operating system schedules the producer and consumer threads, then we 
have the same quirk in mind.

When I wrote the first version of this test (which may be virtually 
identical to the one that's being run), it never occurred to me that a 
container wouldn't cache its size, so the queue's push_back method is 
much less efficient than it should be.  It should call empty() before 
insert(), and then signal when appropriate.  Otherwise, it may traverse 
the entire sequence before discovering that its length is (not) 1.  
Oops!

>  BTW, all these tests are artificial (IMHO w.r.t. good thread design)
>  in that they over-stress the communication between threads

I agree, but I don't think the good designs produce meaningful 
statistics.  In the spirit of the older tests, we're just trying to 
exercise the allocator and measure how long it took to do so.


Felix