linux-kernel - [PATCH] mm: hugetlb: bail out unmapping after serving reference page

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Message-ID: <CAJd=RBALNtedfq+PLPnGKd4i4D0mLiVPdW_7pWWopnSZNC_vqA@mail.gmail.com>
Date:	Wed, 22 Feb 2012 20:35:34 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	Linux-MM <linux-mm@...ck.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, Michal Hocko <mhocko@...e.cz>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Hugh Dickins <hughd@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hillf Danton <dhillf@...il.com>
Subject: [PATCH] mm: hugetlb: bail out unmapping after serving reference page

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@...il.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);
--
--
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