On Wed, Jun 08, 2022 at 08:17:35PM +0800, Miaohe Lin wrote: > +++ b/mm/page_alloc.c > @@ -6771,13 +6771,18 @@ static void __ref memmap_init_compound(struct page *head, > set_page_count(page, 0); > > /* > - * The first tail page stores compound_mapcount_ptr() and > - * compound_order() and the second tail page stores > - * compound_pincount_ptr(). Call prep_compound_head() after > - * the first and second tail pages have been initialized to > - * not have the data overwritten. > + * The first tail page stores compound_mapcount_ptr(), > + * compound_order() and compound_pincount_ptr(). Call > + * prep_compound_head() after the first tail page have > + * been initialized to not have the data overwritten. > + * > + * Note the idea to make this right after we initialize > + * the offending tail pages is trying to take advantage > + * of the likelihood of those tail struct pages being > + * cached given that we will read them right after in > + * prep_compound_head(). It's not that we'll read them again, it's that the cacheline will still be in cache, and therefore dirty. Honestly, I don't think we need this extra explanation in a comment. Just change the first paragraph to reflect reality and leave it at that. > */ > - if (pfn == head_pfn + 2) > + if (unlikely(pfn == head_pfn + 1)) We definitely don't need the unlikely here. > prep_compound_head(head, order); > } > } > > Or am I miss something? > > Thanks! > > > . > > >
