lkml.org 
[lkml]   [2022]   [Jun]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] mm/page_alloc: make calling prep_compound_head more reliable
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!
>
> > .
> >
>

\
 
 \ /
  Last update: 2022-06-14 15:14    [W:0.115 / U:33.552 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site