Re: about buddy and slab allocators

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Bora SAHIN wrote:

Wednesday, June 22, 2005, 1:03:59 PM, you wrote:

Xiangfei> I'm reading a book about kernel memory management. In the book, there is one Xiangfei> sentence saying "with this combination of allocators (buddy and slab Xiangfei> allocators), the kernel can ensure the amount of memory wasted due to Xiangfei> internal fragmentation is kept to a minimum.". From my understanding, I Xiangfei> think the allocators are used to deal with external fragmentation, not Xiangfei> internal. Am I right? Please correct me!!!

Buddy for the external fragmentation...
Slab for the internal fragmentation...

can you clarify external vs internal ?
esp for kernel, which doesnt supply memory to just anyone - only to kernel code.

IIUC, buddy allocators carve up memory into neat 2**n chunks to satisfy requests,
and coalesce contiguous chunks of freed memory back into larger blocks.

FWIW, (not much I think)

$ grep buddy System.map
$ grep slab System.map |wc
    31      93     938


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