Messages in this thread | | | Subject | Re: [PATCH 05/12] mm: alloc_contig_range() added | From | Dave Hansen <> | Date | Thu, 31 Mar 2011 13:28:42 -0700 |
| |
On Thu, 2011-03-31 at 18:26 +0200, Michal Nazarewicz wrote: > > On Thu, 2011-03-31 at 15:16 +0200, Marek Szyprowski wrote: > >> + ret = 0; > >> + while (!PageBuddy(pfn_to_page(start & (~0UL << ret)))) > >> + if (WARN_ON(++ret >= MAX_ORDER)) > >> + return -EINVAL; > > On Thu, 31 Mar 2011 18:02:41 +0200, Dave Hansen wrote: > > Holy cow, that's dense. Is there really no more straightforward way to > > do that? > > Which part exactly is dense? What would be qualify as a more > straightforward way?
I'm still not 100% sure what it's trying to do. It looks like it attempts to check all of "start"'s buddy pages.
unsigned long find_buddy(unsigned long pfn, int buddy) { unsigned long page_idx = pfn & ((1 << MAX_ORDER) - 1); // You had a macro for this I think unsigned long buddy_idx = __find_buddy_index(page_idx, order); return page_idx + buddy_idx; }
Is something like this equivalent?
int order; for (order = 0; order <= MAX_ORDER; order++) { unsigned long buddy_pfn = find_buddy(start, order); struct page *buddy = pfn_to_page(buddy_pfn); if (PageBuddy(buddy) break; WARN(); return -EINVAL; }
I'm wondering also if you can share some code with __rmqueue().
> > In any case, please pull the ++ret bit out of the WARN_ON(). Some > > people like to do: > > > > #define WARN_ON(...) do{}while(0) > > > > to save space on some systems. > > I don't think that's the case. Even if WARN_ON() decides not to print > a warning, it will still return the value of the argument. If not, > a lot of code will brake.
Bah, sorry. I'm confusing WARN_ON() and WARN().
-- Dave
| |