On Tue, Jan 22, 2019 at 04:16:28PM +0100, Michal Hocko wrote:
>On Tue 22-01-19 15:07:17, Wei Yang wrote:
>> 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.
>
>Does this lead to a better code generation? Does it make the code easier
>to read/maintain?
>
I think the answer is yes.
* it reduce the code from 6 lines to 3 lines, 50% off
* by reducing calculation back and forth, it would be easier for
audience to catch what it tries to do
>> >> * 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?
>
>yes AFAICS
ok, maybe the first time to know this. So I guess they are the same
meaning? I searched in google, but no specific explanation on this.
>
>--
>Michal Hocko
>SUSE Labs
--
Wei Yang
Help you, Help me
