[boost.thread] function call and functor in thread creation: performance
Hi, everyone, A new thread can be created using boost thread either from a function or a functor as the entry point of the new thread, as: void thread_function(); boost::thread thrd(&function); class functor { public: inline void operator()(); }; functor f; boost::thread thrd(f); Is there a performance difference between these two? In an ordinary C++ program, can I claim that calling f() 1000 times gives better performance than calling thread_function() 1000 times, because the functor is hinted "inline" even the hint is igored by my compiler? Is f() the same as a function call in term of performance? Thanks in advance. Robert
AMDG On 1/21/2011 5:55 PM, Boost lzw wrote:
A new thread can be created using boost thread either from a function or a functor as the entry point of the new thread, as:
void thread_function(); boost::thread thrd(&function);
class functor { public: inline void operator()(); }; functor f; boost::thread thrd(f);
Is there a performance difference between these two?
In an ordinary C++ program, can I claim that calling f() 1000 times gives better performance than calling thread_function() 1000 times, because the functor is hinted "inline" even the hint is igored by my compiler? Is f() the same as a function call in term of performance?
The cost if creating the thread almost certainly swamps the function call overhead. Even ignoring this, if the work the function does is trivial enough that inlining matters, then you probably shouldn't be spawning a thread for it anyway. In Christ, Steven Watanabe
I tend to think the job that a thread does is non-trivial. Does this mean
that I should never try to inline the function call operator? Does anyone
know the performance difference between creating a new boost thread via
ordinary function vs. doing that via a functor?
Thanks
On Fri, Jan 21, 2011 at 11:53 PM, Steven Watanabe
AMDG
On 1/21/2011 5:55 PM, Boost lzw wrote:
A new thread can be created using boost thread either from a function or a functor as the entry point of the new thread, as:
void thread_function(); boost::thread thrd(&function);
class functor { public: inline void operator()(); }; functor f; boost::thread thrd(f);
Is there a performance difference between these two?
In an ordinary C++ program, can I claim that calling f() 1000 times gives better performance than calling thread_function() 1000 times, because the functor is hinted "inline" even the hint is igored by my compiler? Is f() the same as a function call in term of performance?
The cost if creating the thread almost certainly swamps the function call overhead. Even ignoring this, if the work the function does is trivial enough that inlining matters, then you probably shouldn't be spawning a thread for it anyway.
In Christ, Steven Watanabe _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
Does anyone know the performance difference between creating a new boost thread via ordinary function vs. doing that via a functor?
As Steven already mentioned, thread launching is so "heavy" procedure, that it's really doesn't matter if you pass a function pointer or boost::function.
participants (3)
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Boost lzw -
Igor R -
Steven Watanabe