From: Andrew Morton <akpm@linux-foundation.org>
To: Hillf Danton <dhillf@gmail.com>
Cc: Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Michal Hocko <mhocko@suse.cz>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Hugh Dickins <hughd@google.com>
Subject: Re: [PATCH] mm: hugetlb: bail out unmapping after serving reference page
Date: Wed, 22 Feb 2012 13:06:59 -0800 [thread overview]
Message-ID: <20120222130659.d75b6f69.akpm@linux-foundation.org> (raw)
In-Reply-To: <CAJd=RBALNtedfq+PLPnGKd4i4D0mLiVPdW_7pWWopnSZNC_vqA@mail.gmail.com>
On Wed, 22 Feb 2012 20:35:34 +0800
Hillf Danton <dhillf@gmail.com> wrote:
> When unmapping given VM range, we could bail out if a reference page is
> supplied and it is unmapped, which is a minor optimization.
>
> Signed-off-by: Hillf Danton <dhillf@gmail.com>
> ---
>
> --- a/mm/hugetlb.c Wed Feb 22 19:34:12 2012
> +++ b/mm/hugetlb.c Wed Feb 22 19:50:26 2012
> @@ -2280,6 +2280,9 @@ void __unmap_hugepage_range(struct vm_ar
> if (pte_dirty(pte))
> set_page_dirty(page);
> list_add(&page->lru, &page_list);
> +
> + if (page == ref_page)
> + break;
> }
> spin_unlock(&mm->page_table_lock);
> flush_tlb_range(vma, start, end);
Perhaps add a little comment to this explaining what's going on?
It would be sufficient to do
if (ref_page)
break;
This is more efficient, and doesn't make people worry about whether
this value of `page' is the same as the one which
pte_page(huge_ptep_get()) earlier returned.
Why do we evaluate `page' twice inside that loop anyway? And why do we
check for huge_pte_none() twice? It looks all messed up.
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next prev parent reply other threads:[~2012-02-22 21:07 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-22 12:35 [PATCH] mm: hugetlb: bail out unmapping after serving reference page Hillf Danton
2012-02-22 21:06 ` Andrew Morton [this message]
2012-02-23 13:05 ` Hillf Danton
2012-02-23 20:12 ` Andrew Morton
2012-03-21 21:00 ` Andrew Morton
2012-03-22 13:21 ` Hillf Danton
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