Commit f1e61557f023 ("mm: pack compound_dtor and compound_order into one word
in struct page") changed compound_dtor from a pointer to an array index in
order to pack it. To check if page has the hugeltbfs compound_dtor, we can
just compare the index directly without fetching the function pointer.
Said commit did that with PageHuge() and we can do the same with PageHeadHuge()
to make the code a bit smaller and faster.
Signed-off-by: Vlastimil Babka <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
---
mm/hugetlb.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index dd8737a94bec..ba1ca452aa7f 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1313,7 +1313,7 @@ int PageHeadHuge(struct page *page_head)
if (!PageHead(page_head))
return 0;
- return get_compound_page_dtor(page_head) == free_huge_page;
+ return page_head[1].compound_dtor == HUGETLB_PAGE_DTOR;
}
pgoff_t __basepage_index(struct page *page)
--
2.25.1
On 3/11/20 10:24 AM, Vlastimil Babka wrote:
> Commit f1e61557f023 ("mm: pack compound_dtor and compound_order into one word
> in struct page") changed compound_dtor from a pointer to an array index in
> order to pack it. To check if page has the hugeltbfs compound_dtor, we can
> just compare the index directly without fetching the function pointer.
> Said commit did that with PageHuge() and we can do the same with PageHeadHuge()
> to make the code a bit smaller and faster.
>
> Signed-off-by: Vlastimil Babka <[email protected]>
> Cc: Mike Kravetz <[email protected]>
> Cc: Kirill A. Shutemov <[email protected]>
Thanks!
Reviewed-by: Mike Kravetz <[email protected]>
--
Mike Kravetz
On Wed, 11 Mar 2020, Vlastimil Babka wrote:
> Commit f1e61557f023 ("mm: pack compound_dtor and compound_order into one word
> in struct page") changed compound_dtor from a pointer to an array index in
> order to pack it. To check if page has the hugeltbfs compound_dtor, we can
> just compare the index directly without fetching the function pointer.
> Said commit did that with PageHuge() and we can do the same with PageHeadHuge()
> to make the code a bit smaller and faster.
>
> Signed-off-by: Vlastimil Babka <[email protected]>
> Cc: Mike Kravetz <[email protected]>
> Cc: Kirill A. Shutemov <[email protected]>
Fixes: f1e61557f023 ("mm: pack compound_dtor and compound_order into one
word in struct page")
Acked-by: David Rientjes <[email protected]>
[+nehaagarwal]
We've been running with this patch for a few years and it works as
intended.
> ---
> mm/hugetlb.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index dd8737a94bec..ba1ca452aa7f 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1313,7 +1313,7 @@ int PageHeadHuge(struct page *page_head)
> if (!PageHead(page_head))
> return 0;
>
> - return get_compound_page_dtor(page_head) == free_huge_page;
> + return page_head[1].compound_dtor == HUGETLB_PAGE_DTOR;
> }
>
> pgoff_t __basepage_index(struct page *page)
On Wed, Mar 11, 2020 at 06:24:40PM +0100, Vlastimil Babka wrote:
> Commit f1e61557f023 ("mm: pack compound_dtor and compound_order into one word
> in struct page") changed compound_dtor from a pointer to an array index in
> order to pack it. To check if page has the hugeltbfs compound_dtor, we can
> just compare the index directly without fetching the function pointer.
> Said commit did that with PageHuge() and we can do the same with PageHeadHuge()
> to make the code a bit smaller and faster.
>
> Signed-off-by: Vlastimil Babka <[email protected]>
> Cc: Mike Kravetz <[email protected]>
> Cc: Kirill A. Shutemov <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
We use literaly the same check in the function next to this one --
PageHuge().
--
Kirill A. Shutemov
On Thu, Mar 12, 2020 at 03:41:19AM +0300, Kirill A. Shutemov wrote:
> On Wed, Mar 11, 2020 at 06:24:40PM +0100, Vlastimil Babka wrote:
> > Commit f1e61557f023 ("mm: pack compound_dtor and compound_order into one word
> > in struct page") changed compound_dtor from a pointer to an array index in
> > order to pack it. To check if page has the hugeltbfs compound_dtor, we can
> > just compare the index directly without fetching the function pointer.
> > Said commit did that with PageHuge() and we can do the same with PageHeadHuge()
> > to make the code a bit smaller and faster.
> >
> > Signed-off-by: Vlastimil Babka <[email protected]>
> > Cc: Mike Kravetz <[email protected]>
> > Cc: Kirill A. Shutemov <[email protected]>
>
> Acked-by: Kirill A. Shutemov <[email protected]>
>
> We use literaly the same check in the function next to this one --
> PageHuge().
Ugh.. I have to read the commit message, not only the code :P
--
Kirill A. Shutemov