[Bug libstdc++/96942] std::pmr::monotonic_buffer_resource causes CPU cache misses

[amonakov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96942

--- Comment #14 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
> It adds 11 bytes to the size given to the constructor (for its internal
> bookkeeping) and then rounds up to a power of two.

What is the purpose of this rounding up?