> AA> You can fix the problem in userspace by using a meaningful 'addr' as
> AA> hint to mmap(2), or by using MAP_FIXED from userspace, then the kernel
> AA> won't waste time searching the first available mapping over
> AA> TASK_UNMAPPED_BASE.
> Well. Really you can't do this, because you can not really track all of
> the mappings in user program as glibc and probably other libraries
> use mmap for their purposes.
There's no reason we couldn't do this hint in kernel space.
In arch_get_unmapped_area we can simply keep track of the
lowest address where we found free space, while on munmap()
we can adjust this hint if needed.
OTOH, I doubt it would help real-world workloads where the
application maps and unmaps areas of different sizes and
actually does something with the memory instead of just
mapping and unmapping it ;)))
kind regards,
Rik
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