Windows large pages, Linux huge pages, macOS super pages support

large_huge_super_pages.md

Large, Huge, Super Pages

Linux Huge Pages

Transparent Huge Pages (THP) via madvice

Not covered here, see https://www.kernel.org/doc/Documentation/vm/transhuge.txt

Allocating huge pages using mmap

See https://www.kernel.org/doc/Documentation/vm/hugetlbpage.txt

Huge pages cannot be swapped out under memory pressure.

Verify that kernel supports Huge pages cat /proc/meminfo:

HugePages_Total: uuu
HugePages_Free:  vvv
HugePages_Rsvd:  www
HugePages_Surp:  xxx
Hugepagesize:    yyy kB
Hugetlb:         zzz kB

Hugepagesize is most probably 2MB.

Set up size of kernel huge pages pool (512 pages * 2MB = 1GB)

sudo sysctl -w vm.nr_hugepages=512

It's better be done early at the startup. This could fail due to memory fragmentation. Add this to /etc/sysctl.conf:

vm.nr_hugepages = 512

macOS Super Pages

macOS has no superpages support (aka Huge Pages (Linux), aka Large Pages (Windows)) on Apple silicon.

Theoretically you could use VM_FLAGS_SUPERPAGE_SIZE_2MB or VM_FLAGS_SUPERPAGE_SIZE_ANY flags, which are defined in <mach/mach_vm.h>

You could profive those flags to mac_vm_allocate() directly, or pass them in the highest bits of file desciptor of mmap():

mmap(0, superpage_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, VM_FLAGS_SUPERPAGE_SIZE_2MB, 0);

Example from tests/superpages/testsp.c

Unfortunately that doesn't work on M1/M2. The only platform that has superpages support is x86_64. It supports 2MB pages. None of the other platforms seems to support it.

osfmk/vm/vm_map.c

arm/pmap/pmap.h