On Sun, Mar 19, 2017 at 11:08:22AM -0400, Michal Hocko wrote: >On Sun 19-03-17 23:03:45, Wei Yang wrote: >> On Sun, Mar 19, 2017 at 10:30:13AM -0400, Michal Hocko wrote: >> >On Sat 18-03-17 08:39:14, Wei Yang wrote: >> >> The field page->flags is defined as unsigned long and is divided into >> >> several parts to store different information of the page, like section, >> >> node, zone. Which means all parts must sit in the one "unsigned >> >> long". >> >> >> >> BITS_PER_LONG is used in several places to ensure this applies. >> >> >> >> #if SECTIONS_WIDTH+NODES_WIDTH+ZONES_WIDTH > BITS_PER_LONG - NR_PAGEFLAGS >> >> #if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS >> >> #if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_CPUPID_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS >> >> >> >> While we use "sizeof(unsigned long) * 8" in the definition of >> >> SECTIONS_PGOFF >> >> >> >> #define SECTIONS_PGOFF ((sizeof(unsigned long)*8) - SECTIONS_WIDTH) >> >> >> >> This may not be that obvious for audience to catch the point. >> >> >> >> This patch replaces the "sizeof(unsigned long) * 8" with BITS_PER_LONG to >> >> make all this consistent. >> > >> >I am not really sure this is an improvement. page::flags is unsigned >> >long nad the current code reflects that type. >> > >> >> Hi, Michal >> >> Glad to hear from you. >> >> I think the purpose of definition BITS_PER_LONG is more easily to let audience >> know it is the number of bits of type long. If it has no improvement, we don't >> need to define a specific macro . >> >> And as you could see, several related macros use BITS_PER_LONG in their >> definition. After this change, all of them will have a consistent definition. >> >> After this change, code looks more neat :-) >> >> So it looks more reasonable to use this. > >I do not think that this is sufficient to justify the change. > Fine~ Thanks for comments~ >-- >Michal Hocko >SUSE Labs -- Wei Yang Help you, Help me
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