malloc: Add Huge Page support for mmap

System Internals / glibc - Adhemerval Zanella [] - 15 December 2021 20:35 UTC

With the morecore hook removed, there is not easy way to provide huge pages support on with glibc allocator without resorting to transparent huge pages. And some users and programs do prefer to use the huge pages directly instead of THP for multiple reasons: no splitting, re-merging by the VM, no TLB shootdowns for running processes, fast allocation from the reserve pool, no competition with the rest of the processes unlike THP, no swapping all, etc.

This patch extends the 'glibc.malloc.hugetlb' tunable: the value '2' means to use huge pages directly with the system default size, while a positive value means and specific page size that is matched against the supported ones by the system.

Currently only memory allocated on sysmalloc() is handled, the arenas still uses the default system page size.

To test is a new rule is added tests-malloc-hugetlb2, which run the addes tests with the required GLIBC_TUNABLE setting. On systems without a reserved huge pages pool, is just stress the mmap(MAP_HUGETLB) allocation failure. To improve test coverage it is required to create a pool with some allocated pages.

Checked on x86_64-linux-gnu.

98d5fcb8d0 malloc: Add Huge Page support for mmap
NEWS | 8 +-
Rules | 17 ++++
elf/dl-tunables.list | 3 +-
elf/tst-rtld-list-tunables.exp | 2 +-
malloc/Makefile | 8 +-
malloc/arena.c | 4 +-
malloc/malloc.c | 31 ++++++-
manual/tunables.texi | 7 ++
sysdeps/generic/malloc-hugepages.c | 8 ++
sysdeps/generic/malloc-hugepages.h | 7 ++
sysdeps/unix/sysv/linux/malloc-hugepages.c | 127 +++++++++++++++++++++++++++++
11 files changed, 207 insertions(+), 15 deletions(-)


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