On Mon 17-08-15 18:09:04, Kirill A. Shutemov wrote: > The patch halves space occupied by compound_dtor and compound_order in > struct page. > > For compound_order, it's trivial long -> int/short conversion. > > For get_compound_page_dtor(), we now use hardcoded table for destructor > lookup and store its index in the struct page instead of direct pointer > to destructor. It shouldn't be a big trouble to maintain the table: we > have only two destructor and NULL currently. > > This patch free up one word in tail pages for reuse. This is preparation > for the next patch. > > Signed-off-by: Kirill A. Shutemov <[email protected]>
Reviewed-by: Michal Hocko <[email protected]> [...] > @@ -145,8 +143,13 @@ struct page { > */ > /* First tail page of compound page */ > struct { > - compound_page_dtor *compound_dtor; > - unsigned long compound_order; > +#ifdef CONFIG_64BIT > + unsigned int compound_dtor; > + unsigned int compound_order; > +#else > + unsigned short int compound_dtor; > + unsigned short int compound_order; > +#endif > }; Why do we need this ifdef? We can go with short for both 32b and 64b AFAICS. We do not use compound_order for anything else than the order, right? While I am looking at this, it seems we are jugling with type for order quite a lot - int, unsing int and even unsigned long. -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
