From: David Rientjes <rientjes@google.com>
To: Vlastimil Babka <vbabka@suse.cz>, Neha Agarwal <nehaagarwal@google.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH] mm/hugetlb: remove unnecessary memory fetch in PageHeadHuge()
Date: Wed, 11 Mar 2020 12:25:20 -0700 (PDT) [thread overview]
Message-ID: <alpine.DEB.2.21.2003111223090.171292@chino.kir.corp.google.com> (raw)
In-Reply-To: <20200311172440.6988-1-vbabka@suse.cz>
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 <vbabka@suse.cz>
> Cc: Mike Kravetz <mike.kravetz@oracle.com>
> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Fixes: f1e61557f023 ("mm: pack compound_dtor and compound_order into one
word in struct page")
Acked-by: David Rientjes <rientjes@google.com>
[+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)
next prev parent reply other threads:[~2020-03-11 19:25 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-11 17:24 [PATCH] mm/hugetlb: remove unnecessary memory fetch in PageHeadHuge() Vlastimil Babka
2020-03-11 18:20 ` Mike Kravetz
2020-03-11 19:25 ` David Rientjes [this message]
2020-03-11 19:25 ` David Rientjes
2020-03-12 0:41 ` Kirill A. Shutemov
2020-03-12 0:42 ` Kirill A. Shutemov
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