how to do page level mem alloc in freebsd kernel?
kalash.nainwal at gmail.com
Thu Jul 15 15:34:16 UTC 2010
2010/7/15 Kostik Belousov <kostikbel at gmail.com>:
> On Thu, Jul 15, 2010 at 08:24:53PM +0530, kalash nainwal wrote:
>> On Thu, Jul 15, 2010 at 5:41 PM, John Baldwin <jhb at freebsd.org> wrote:
>> > On Thursday, July 15, 2010 6:28:53 am kalash nainwal wrote:
>> >> Hi,
>> >> I want to allocate one (or more) pages in kernel space.
>> >> I'm not sure what is the api in freebsd (something which
>> >> is similar to __get_free_pages() of linux).
>> >> Would malloc(4096, ...) guarantee that the returned
>> >> address is aligned on page boundary?
>> > Well, malloc(PAGE_SIZE) will align it on a page boundary. :) malloc(4096)
>> > will be aligned on a 4096-byte boundary if PAGE_SIZE is >= 4096. My
>> > understanding is that objects returned from malloc() are aligned to the
>> > smallest power-of-2 value >= the requested size up to a page. Allocations
>> > larger than a page are page aligned. So a malloc of 24 bytes or 32 bytes is
>> > 32-byte aligned for example.
>> Thanks John for explaining.
>> After going through the kernel src I was not sure about
>> malloc, as the code is little hard to follow. However I figured
>> kmem_alloc(kernel_pmap, PAGE_SIZE) would serve my
oops. my bad. thanks for correcting.
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