Re: [PATCH 1/2] mm/pageblock: mitigation cmpxchg false sharing in pageblock flags

[Alex Shi]

在 2020/8/16 下午12:09, Matthew Wilcox 写道:
> On Sun, Aug 16, 2020 at 11:47:56AM +0800, Alex Shi wrote:
>> +++ b/mm/page_alloc.c
>> @@ -467,6 +467,8 @@ static inline int pfn_to_bitidx(struct page *page, unsigned long pfn)
>>  	return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS;
>>  }
>>  
>> +#define BITS_PER_CHAR	8
> 
> include/linux/bits.h:#define BITS_PER_BYTE              8

Thank for reminder!

> 
>>  	bitmap = get_pageblock_bitmap(page, pfn);
>>  	bitidx = pfn_to_bitidx(page, pfn);
>> -	word_bitidx = bitidx / BITS_PER_LONG;
>> -	bitidx &= (BITS_PER_LONG-1);
>> +	word_bitidx = bitidx / BITS_PER_CHAR;
>> +	bitidx &= (BITS_PER_CHAR-1);
> 
> It's not a word any more.  it's a byte.
> 

Yes, will change this.
Thanks!