Hi all, Before I switch to using boost::make_shared<> I wanted to test its purported performance advantage. I created a simple benchmark for measuing raw allocation throughput for 3 classes of different sizes with a common base class (constructors and destructors trivial). The number of allocations was set to 40,000,000 as it was roughly giving me 10 seconds running time per test. Unfortunatelly it turns out that on VC++9 (release target with default optimizations) boost::make_shared is significantly slower than simply doing boost::shared_ptr(new). Here's the benchmark output: TestBoostMakeShared 10.577s 3.78179e+006 allocs/s TestBoostSharedPtrNew 8.907s 4.49085e+006 allocs/s As you can see boost::make_shared is over 15% slower than boost::shared_ptr(new) idiom. Having available VC++10 compiler as well I then compared these results with std::shared_ptr and std::make_shared implementations that come with that compiler (but not VC++9). Here are the results: TestBoostMakeShared 9.688s 4.12882e+006 allocs/s TestBoostSharedPtrNew 8.252s 4.84731e+006 allocs/s TestStdMakeShared 5.07s 7.88955e+006 allocs/s TestStdSharedPtrNew 8.159s 4.90256e+006 allocs/s While std::shared_ptr(new) performs about the same as boost::shared_ptr(new), std::make_shared really blows away boost::make_shared and both shared_ptr(new) tests, being almost twice as fast as boost::make_shared. I then profiled the boost::make_shared test to see what's the biggest performance bottleneck when compared to boost::shared_ptr(new) profiler run. The culprit was immediately obvious: boost::make_shared test was spending above 25% of its time in "type_info::operator==(class type_info const &) const" function. This function was being called indirectly from boost::make_shared through boost::get_deleter. After digging some more through the implementation I came to the conclusion that, in this particular case, we are guaranteed to always be requesting deleter for the right class (namely T from boost::make_shared<T>). Since boost::shared_ptr doesn't have a way to retrieve the deleter without using RTTI I decided to add one and use it from an alternative boost::make_shared. So I did the following: 1. I added a virtual function to detail::sp_counted_base (detail\sp_counted_base_w32.hpp): virtual void * get_raw_deleter( ) = 0; 2. I implemented get_raw_deleter() function in sp_counted_impl_p (detail\sp_counted_impl.hpp): virtual void * get_raw_deleter( ) { return 0; } 3. I implemented get_raw_deleter() function in sp_counted_impl_pd (detail\sp_counted_impl.hpp): virtual void * get_raw_deleter( ) { return &reinterpret_cast<char&>( del ); } 4. I implemented get_raw_deleter() function in sp_counted_impl_pda (detail\sp_counted_impl.hpp): virtual void * get_raw_deleter( ) { return &reinterpret_cast<char&>( d_ ); } 5. I added the following function to detail::shared_count: void * get_raw_deleter( ) const { return pi_? pi_->get_raw_deleter( ): 0; } 6. I added the following function to shared_ptr<>: void * _internal_get_raw_deleter( ) const { return pn.get_raw_deleter( ); } 7. I made a separate copy of boost::make_shared function and replaced a single line from: boost::detail::sp_ms_deleter< T > * pd = boost::get_deleter< boost::detail::sp_ms_deleter< T > >( pt ); to: boost::detail::sp_ms_deleter< T > * pd = static_cast<boost::detail::sp_ms_deleter< T > *>(pt._internal_get_raw_deleter()); Benchmarking the results afterwards gave me the following results on VC++9: TestBoostSharedPtrNew 9.204s 4.34594e+006 allocs/s TestBoostMakeShared 10.499s 3.80989e+006 allocs/s TestBoostMakeSharedAlt 7.831s 5.1079e+006 allocs/s My changes translated into almost 35% improvement in allocation speed over the current implementation of boost::make_shared. Or to put it differently, they amount to 25+% decrease in running time as we could have supposed from the profiling results. Results on VC++10 are similar: TestBoostSharedPtrNew 8.487s 4.71309e+006 allocs/s TestBoostMakeShared 9.609s 4.16276e+006 allocs/s TestStdSharedPtrNew 8.283s 4.82917e+006 allocs/s TestStdMakeShared 5.039s 7.93808e+006 allocs/s TestBoostMakeSharedAlt 6.802s 5.88062e+006 allocs/s VC++10's std::make_shared is still much faster (almost 35% faster than boost::shared_ptr) and we will be switching to it once we switch to VC++10. But in the meantime it seems to me that boost::make_shared should be fixed to improve the performance. Again, this is only one compiler and other compilers might not have such a severe RTTI performance issue but I still think it would be well worth avoiding unnecessary calls to RTTI during performance-relevant operations such as heap allocations. The testing and changes were done on Boost 1.48.0 but I compared Smart Ptr library sources with Boost 1.49.0 and the above changes should work there equally well. Thanks, Ivan