linux-kernel - [PATCHv12 08/37] khugepaged: ignore pmd tables with THP mapped with ptes

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Date:	Tue,  6 Oct 2015 18:23:35 +0300
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Hugh Dickins <hughd@...gle.com>
Cc:	Dave Hansen <dave.hansen@...el.com>, Mel Gorman <mgorman@...e.de>,
	Rik van Riel <riel@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Christoph Lameter <cl@...two.org>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Steve Capper <steve.capper@...aro.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	Jerome Marchand <jmarchan@...hat.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCHv12 08/37] khugepaged: ignore pmd tables with THP mapped with ptes

Prepare khugepaged to see compound pages mapped with pte. For now we
won't collapse the pmd table with such pte.

khugepaged is subject for future rework wrt new refcounting.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Tested-by: Sasha Levin <sasha.levin@...cle.com>
Tested-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
Acked-by: Jerome Marchand <jmarchan@...hat.com>
Acked-by: Vlastimil Babka <vbabka@...e.cz>
---
 include/trace/events/huge_memory.h | 1 +
 mm/huge_memory.c                   | 9 ++++++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
index 1efc7f1dc9bd..11c59ca5e145 100644
--- a/include/trace/events/huge_memory.h
+++ b/include/trace/events/huge_memory.h
@@ -22,6 +22,7 @@
 	EM( SCAN_PAGE_LRU,		"page_not_in_lru")		\
 	EM( SCAN_PAGE_LOCK,		"page_locked")			\
 	EM( SCAN_PAGE_ANON,		"page_not_anon")		\
+	EM( SCAN_PAGE_COMPOUND,		"page_compound")		\
 	EM( SCAN_ANY_PROCESS,		"no_process_for_page")		\
 	EM( SCAN_VMA_NULL,		"vma_null")			\
 	EM( SCAN_VMA_CHECK,		"vma_check_failed")		\
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index c41e107bddc1..7524618a923c 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -46,6 +46,7 @@ enum scan_result {
 	SCAN_PAGE_LRU,
 	SCAN_PAGE_LOCK,
 	SCAN_PAGE_ANON,
+	SCAN_PAGE_COMPOUND,
 	SCAN_ANY_PROCESS,
 	SCAN_VMA_NULL,
 	SCAN_VMA_CHECK,
@@ -2881,6 +2882,13 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
 			result = SCAN_PAGE_NULL;
 			goto out_unmap;
 		}
+
+		/* TODO: teach khugepaged to collapse THP mapped with pte */
+		if (PageCompound(page)) {
+			result = SCAN_PAGE_COMPOUND;
+			goto out_unmap;
+		}
+
 		/*
 		 * Record which node the original page is from and save this
 		 * information to khugepaged_node_load[].
@@ -2893,7 +2901,6 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
 			goto out_unmap;
 		}
 		khugepaged_node_load[node]++;
-		VM_BUG_ON_PAGE(PageCompound(page), page);
 		if (!PageLRU(page)) {
 			result = SCAN_SCAN_ABORT;
 			goto out_unmap;
-- 
2.5.3

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