On Tue, Jan 22, 2019 at 09:55:24AM +0100, Michal Hocko wrote: >On Sat 19-01-19 07:49:05, Wei Yang wrote: >> Two cleanups in this patch: >> >> * since pageblock_nr_pages == (1 << pageblock_order), the roundup() >> and right shift pageblock_order could be replaced with >> DIV_ROUND_UP() > >Why is this change worth it? > To make it directly show usemapsize is number of times of pageblock_nr_pages. >> * use BITS_TO_LONGS() to get number of bytes for bitmap >> >> This patch also fix one typo in comment. >> >> Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx> >> --- >> mm/page_alloc.c | 9 +++------ >> 1 file changed, 3 insertions(+), 6 deletions(-) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index d295c9bc01a8..d7073cedd087 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -6352,7 +6352,7 @@ static void __init calculate_node_totalpages(struct pglist_data *pgdat, >> /* >> * Calculate the size of the zone->blockflags rounded to an unsigned long >> * Start by making sure zonesize is a multiple of pageblock_order by rounding >> - * up. Then use 1 NR_PAGEBLOCK_BITS worth of bits per pageblock, finally >> + * up. Then use 1 NR_PAGEBLOCK_BITS width of bits per pageblock, finally > >why do you change this? > Is the original comment not correct? Or I misunderstand the English word? >> * round what is now in bits to nearest long in bits, then return it in >> * bytes. >> */ >> @@ -6361,12 +6361,9 @@ static unsigned long __init usemap_size(unsigned long zone_start_pfn, unsigned l >> unsigned long usemapsize; >> >> zonesize += zone_start_pfn & (pageblock_nr_pages-1); >> - usemapsize = roundup(zonesize, pageblock_nr_pages); >> - usemapsize = usemapsize >> pageblock_order; >> + usemapsize = DIV_ROUND_UP(zonesize, pageblock_nr_pages); >> usemapsize *= NR_PAGEBLOCK_BITS; >> - usemapsize = roundup(usemapsize, 8 * sizeof(unsigned long)); >> - >> - return usemapsize / 8; >> + return BITS_TO_LONGS(usemapsize) * sizeof(unsigned long); >> } >> >> static void __ref setup_usemap(struct pglist_data *pgdat, >> -- >> 2.15.1 >> > >-- >Michal Hocko >SUSE Labs -- Wei Yang Help you, Help me
