GlobalMemoryBarrier blocks until "all running threads [in the host OS] have passed through a state where all memory accesses to user-space addresses match program order between entry to and return from [GlobalMemoryBarrier]", as for membarrier(2).

HaveGlobalMemoryBarrier returns true if GlobalMemoryBarrier is supported.

HaveProcessMemoryBarrier returns true if ProcessMemoryBarrier is supported.

NotifyCurrentMemcgPressureCallback requests that f is called whenever the calling process' memory cgroup indicates memory pressure of the given level, as specified by Linux's Documentation/cgroup-v1/memory.txt.

ProcessMemoryBarrier is equivalent to GlobalMemoryBarrier, but only synchronizes with threads sharing a virtual address space (from the host OS' perspective) with the calling thread.