Thanks! On Thu, Jan 10, 2019 at 12:51 AM Okash Khawaja <okash.khawaja@gmail.com> wrote:

On Wed, Jan 9, 2019 at 3:17 PM Carter Cheng <cartercheng@gmail.com> wrote:

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Hi,

I am curious where in the kernel sources would I find the kmalloc

implementation? I am curious how GFP_ATOMIC option is implemented.

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Thanks,

Carter.

Hi Carter,

kmalloc() implementation can be found in include/linux/slab.h. Interesting part of kmalloc() is the use of kmem_cache. kmem_cache is basically a pool of memory. kmalloc() maintains a system of kmem_cache's and allocates memory from those caches to the caller. How it allocates that memory is determined by type of request (e.g. GFP_ATOMIC) and "buddy system" algorithm, which is an algorithm designed to minimise fragmentation and be cache efficient.

From what I remember, kmalloc system sets aside memory for "emergency" uses, like kmalloc calls with GFP_ATOMIC. So for normal memory allocation calls, execution may sleep until memory becomes available, even though there may be memory available in the emergence cache.

Hope it helps :)

Okash

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