[Bug libstdc++/13823] Significant performance issue with std::map on multiple threads on dual processor - possibly default allocator

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=13823

--- Comment #14 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Dan Evison from comment #0)
> This seems to a problem with the default allocator, since running the
> program 
> with GLIBCPP_FORCE_NEW set, removes the problem, and dramatically speeds up 
> the program on two cpus.  (Whereas you may expect a slight degradation).

For many, many years now libstdc++ has defaulted to the new_allocator impl for
std::allocator, meaning that it's effectively always GLIBCPP_FORCE_NEW. So I
assume this problem went away, except for people explicitly choosing a
different default allocator (so don't do that).

I'll review all the comments above, but I think we might as well close this.