![]() | ||||||||||
Messages in this thread |
Timur Tabi <timur@freescale.com> writes: > According to LDD3, if I call get_free_pages() to allocate X bytes, I have to > free all of those pages with free_pages(). The VM internals are a little bit > over my head, but I looked at the code and I didn't see why that is a requirement. > > For example, let's say I want to allocated 6MB of physically-contiguous memory. > If I call x = get_free_pages(11) to get 8MB. What happens if I then do > "free_pages(x + 6 * 1024 * 1024, 9)"? > > I remember doing this on the 2.4 kernel, and it never gave me any problems. It is ok, as long as you don't use compound pages (__GFP_COMP) and call split_page() to fix up the reference counts. Also you do this to save memory right? The large system hash code does it too and I used to do it in some 2.4 change with an alloc_pages_exact() which never made it into 2.6. If it's reasonably common we should re-add alloc/get_pages_exact() helper to make this pattern clear and easier to use. -Andi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | |||||||||
| Last update: 2008-04-24 19:31 [from the cache] ©2003-2008 | ||||||||||