c,linux,memory-management,mmap,huge-pages , Using mmap and madvise for huge pages


Using mmap and madvise for huge pages

Question:

Tag: c,linux,memory-management,mmap,huge-pages

I want to allocate memory on the hugepages being used by a Linux machine. I see that there are two ways to do this, using mmap and madvise.

That is, using the MAP_HUGETLB flag with the mmap call -

base_ptr_ = mmap(NULL, memory_size_, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, -1, 0);

And the MADV_HUGEPAGE flag with the madvise call -

madvise(base_ptr_, memory_size_, MADV_HUGEPAGE);

Could someone explain the difference between the two?


Answer:

Both functions perform different operations, which may or may not matter in your context:

The two mechanisms have their own doc file in the kernel tree: hugetlbpage.txt and transhuge.txt


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