[PATCH] D71975: [Support] Support MF_HUGE_HINT for Linux and FreeBSD

[Bruno Ricci via Phabricator via llvm-commits]

riccibruno created this revision.
riccibruno added reviewers: bsdjhb, dim, t.p.northover, psmith, rnk.
riccibruno added a project: LLVM.
Herald added subscribers: llvm-commits, hiraditya, krytarowski, arichardson, emaste.

Implement support for large page requests with the `allocateMappedMemory` interface on Linux and FreeBSD. If the `MF_HUGE_HINT` flag is passed we first try an `mmap` with the relevant flag. If that fails we fall back to a normal `mmap`. On some systems (such as Linux with transparent huge pages) it is possible to indicate with `madvise` that a certain range of memory should use large pages. We do this if supported and the first `mmap` with the large page flag failed.

Note that only a little test is added since the `allocateMappedMemory` interface is already well-tested. It seems difficult to reliably test that we got large pages. I am open to suggestions here (maybe with `userfaultfd` ?).


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D71975

Files:
  llvm/include/llvm/Support/Memory.h
  llvm/lib/Support/Unix/Memory.inc
  llvm/unittests/Support/MemoryTest.cpp

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