Messages in this thread | | | Date | Wed, 22 Oct 2008 22:42:12 +0400 | From | Cyrill Gorcunov <> | Subject | Re: [RFC] SLUB - define OO_ macro instead of hardcoded numbers |
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[Christoph Lameter - Wed, Oct 22, 2008 at 11:24:58AM -0700] > On Wed, 22 Oct 2008, Cyrill Gorcunov wrote: > >> [Christoph Lameter - Wed, Oct 22, 2008 at 11:10:56AM -0700] >>> On Wed, 22 Oct 2008, Cyrill Gorcunov wrote: >>> >>>> +#define OO_SHIFT 16 >>>> +#define OO_MASK ((1 << OO_SHIFT) - 1) >>>> +#define MAX_OBJS_PER_PAGE 65535 /* see struct page.objects */ >>> >>> This is == OO_MASK right? Otherwise things will break when we change >>> OO_SHIFT. >>> >> >> Yes, I set it 65535 directly to distinguish it from OO_MASK >> meaning not value and point to page.objects since they are >> u16. Which meant that is the point where all limits start. >> So it we set OO_SHIFT to say 14 it will not be a problem >> but if we exceed 16 bits it will break SLUB. Am I right? >> (I become scratching the head :) > > If you set it > 16 then the size of the field in struct page is violated. > > So > > #define MAX_OBJ_PER_PAGE MIN(1 << bits_in(page.objects) - 1, OO_MASK) > > ? > >
I think the patch becomes more complicated as it should be. Maybe just use:
#define MAX_OBJ_PER_PAGE 65535 /* since page.objects is u16 */
- Cyrill -
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