Re: [Threads-devel] basic_timed_mutex poor performance

Subject: Re: [Threads-devel] basic_timed_mutex poor performance
From: Anthony Williams (anthony_at_[hidden])
Date: 2009-03-30 04:03:10

At Mon 30 Mar 2009 08:43:54 BST, Simon Brangwin <simon_at_[hidden]> wrote:

> The basic_timed_mutex seems to do an awful lot of working in its
> constructor, calling various Gregorian date functions, calendar
> functions, xtime functions doing comparisons etc. This has lead to an
> approximate 5% performance loss for our performance sensitive
> application on the Win32 platform.

Wow, that's huge.

> Is there a way to disable this heavy weight basic_timed_mutex, and use a
> plain old regular mutex ? Are the Boost Threads library maintainers
> aware of the performance penalties from using timed mutex for Windows
> platforms?

The boost 1.35 mutex performance was indeed poor on win32, but this  
did not seem to be due to the date-time dependencies, but due to the  
inefficient use of atomics. The current (1.38) version of the win32  
mutex is comparable or faster than the 1.34 mutex according to my  
benchmarks. I can't remember whether the change made it in to 1.36 or  
whether it had to wait for 1.37.

There may however be a further small gain to be made by stripping out  
the timing stuff from the non-timed mutex, but there is currently no  
way to do this without hacking the code.

Anthony
-- 
Anthony Williams
Author of C++ Concurrency in Action | http://www.manning.com/williams
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