Re: __get_free_pages()

Rik van Riel (H.H.vanRiel@phys.uu.nl)
Wed, 27 May 1998 23:38:48 +0200 (MET DST)


On Wed, 27 May 1998, Andrej Presern wrote:

> Can someone please explain what individual GFP_* bitmasks mean (in
> include/linux/mm.h and as used in __get_free_pages())? Also, what is the
> 'order' argument that __get_free_pages() takes?

The GFP bitmasks have to do with priority, and whether
or not the task can sleep (memory allocation from an
interrupt handler can't sleep, so the GFP_ATOMIC flag
is used).

The 'order' argument is there because the Linux mm
system can hand out pieces of different sizes (who
can't?). Order 0 is 2**0 (is 1) page. Order 5 is
2**5 (is 32) pages.

Rik.
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