Re: [boost] [thread] best practice to lock multiple mutexes

From: Howard Hinnant (hinnant_at_[hidden])
Date: 2008-02-08 17:31:12

On Feb 8, 2008, at 5:22 PM, Peter Dimov wrote:

>> Howard Hinnant:
>>
>>> Here are results (dating around 3 years ago):
>>>
>>> In order:  63 seconds.
>>> try/back off/without yield:  47 seconds.
>>> try/back off/with yield:  34 seconds.
>>
>> With Alexander Terekhov's "swap-based mutex", I'm not seeing a  
>> significant
>> difference between the versions with and without yield. The penalty  
>> likely
>> comes from spin-waits in lock() (which is why they're evil).
>
> There's no significant difference with critical sections, too. Maybe  
> I'm
> doing something wrong. :-)

Or this could be a manifestation of the fact that I never really had  
"hands on" tests with Windows.  I have observed that if the contention  
isn't high, then the algorithm doesn't matter.  Does your test have  
the threads sleeping or otherwise doing independent work?  In mine the  
threads did nothing but fight over the locks.

-Howard