Re: Is there a different memory allocation path other than the buddy allocator?

From: David Hildenbrand
Date: Wed Apr 28 2021 - 10:44:47 EST

On 28.04.21 09:37, Shivank Garg wrote:
Hi Everyone!

I'm understanding memory allocation in Linux and doing some changes in
buddy allocator (__alloc_pages_nodemask) for my experiments. I create
a new flag in `struct page->flags` (by adding a new flag in `enum
pageflags` in `page-flags.h`. I set this bit permanently in
__alloc_pages_nodemask (to not to be cleared once set and survive all
further allocation and freeing). But I'm not able to see expected

I'm guessing this is because Linux is also using some different path
to allocate memory (probably during boot). Is my hypothesis correct?

Is there any different memory allocation path other than buddy
allocator? Where can I find it?

memblock is the early memory allocator during boot, before the buddy is up and running. The range allocator (e.g., alloc_contig_range()) is some kind of mechanism that builds up on top of the buddy. Other allcoators (hugetlb, slab, ...) might cache some pages, but effectively get "physical memory" either via memblock or the buddy.

CMA is another special-purpose allocator which reserves physical memory areas via memblock and then uses the range allocator to actually allocate memory inside these reserved regions at runtime.


David / dhildenb