Comment by jeffbee
There are shared resources involved though, for example one process can cause a lot of traffic in khugepaged. However I would point out that is an endemic risk of Linux's overall architecture. Any process can cause chaos by dirtying pages, or otherwise triggering reclaim.
That’s generally true of any allocator and assuming glibc’s behavior would help mitigate this is critically not something kernel engineers design around nor something glibc allocator is trying to achieve as a design goal.