Re: [boost] [smart_ptr] make_shared performance

Subject: Re: [boost] [smart_ptr] make_shared performance
From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2009-01-16 17:29:16

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On Friday 16 January 2009 16:46 pm, Emil Dotchevski wrote:
> Benchmarks alone don't mean much without understanding your use case.
> What are you trying to do, for which boost::make_shared's performance
> is inadequate?

Nothing, actually.  I was writing some similar code and based it on 
boost/make_shared.hpp.  I simply became curious if make_shared really was any 
faster than using the shared_ptr constructors and new.  Normally, I try not 
to be an optimization nut, but from n2351, it is clear that performance 
optimization is a significant part of the rationale for make_shared existing.  

To quote n2351:

"Besides convenience and style, such a function is also exception safe and 
considerably faster because it can use a single allocation for the object and 
its corresponding control block, eliminating a significant portion of 
shared_ptr's construction overhead. This function eliminates one of the major 
efficiency complaints about shared_ptr."

So it seems reasonable to expect boost::make_shared to provide some observable 
performance benefit.
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