LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
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)

  parent reply	other threads:[~2020-03-11 19:25 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-11 17:24 Vlastimil Babka
2020-03-11 18:20 ` Mike Kravetz
2020-03-11 19:25 ` David Rientjes [this message]
2020-03-12  0:41 ` Kirill A. Shutemov
2020-03-12  0:42   ` Kirill A. Shutemov

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=alpine.DEB.2.21.2003111223090.171292@chino.kir.corp.google.com \
    --to=rientjes@google.com \
    --cc=akpm@linux-foundation.org \
    --cc=kirill.shutemov@linux.intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mike.kravetz@oracle.com \
    --cc=nehaagarwal@google.com \
    --cc=vbabka@suse.cz \
    --subject='Re: [PATCH] mm/hugetlb: remove unnecessary memory fetch in PageHeadHuge()' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).