linux-kernel - [PATCHv2 07/13] mm, thp, tmpfs: initial support for huge page in write_begin/write

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Message-ID: <20131021214722.GH29870@hippobay.mtv.corp.google.com>
Date:	Mon, 21 Oct 2013 14:47:22 -0700
From:	Ning Qu <quning@...gle.com>
To:	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Hugh Dickins <hughd@...gle.com>
Cc:	Al Viro <viro@...iv.linux.org.uk>, Hugh Dickins <hughd@...gle.com>,
	Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
	Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
	Andi Kleen <ak@...ux.intel.com>,
	Matthew Wilcox <willy@...ux.intel.com>,
	Hillf Danton <dhillf@...il.com>, Dave Hansen <dave@...1.net>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Ning Qu <quning@...gle.com>, Ning Qu <quning@...il.com>
Subject: [PATCHv2 07/13] mm, thp, tmpfs: initial support for huge page in
 write_begin/write_end in tmpfs

For now we try to grab a huge cache page if the minimum requirements have been
satisfied.

Signed-off-by: Ning Qu <quning@...il.com>
---
 mm/shmem.c | 30 +++++++++++++++++++++++++-----
 1 file changed, 25 insertions(+), 5 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 0dd6689..af56731 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1635,8 +1635,20 @@ shmem_write_begin(struct file *file, struct address_space *mapping,
 	struct inode *inode = mapping->host;
 	pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 	gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
+	int ret = 0;
+	int getpage_flags = 0;
+
+	/*
+	 * Do not allocate a huge page in the first huge page range in page
+	 * cache. This way we can avoid most small files overhead.
+	 */
+	if (pos >= HPAGE_PMD_SIZE)
+		getpage_flags |= AOP_FLAG_TRANSHUGE;
 
-	return shmem_getpage(inode, index, pagep, SGP_WRITE, gfp, 0, NULL);
+	ret = shmem_getpage(inode, index, pagep, SGP_WRITE, gfp,
+				getpage_flags, NULL);
+
+	return ret;
 }
 
 static int
@@ -1650,10 +1662,18 @@ shmem_write_end(struct file *file, struct address_space *mapping,
 		i_size_write(inode, pos + copied);
 
 	if (!PageUptodate(page)) {
-		if (copied < PAGE_CACHE_SIZE) {
-			unsigned from = pos & (PAGE_CACHE_SIZE - 1);
-			zero_user_segments(page, 0, from,
-					from + copied, PAGE_CACHE_SIZE);
+		if (copied < len) {
+			unsigned from;
+			if (PageTransHugeCache(page)) {
+				from = pos & ~HPAGE_PMD_MASK;
+				zero_huge_user(page, 0, from);
+				zero_huge_user(page, from + copied,
+					       HPAGE_PMD_SIZE);
+			} else {
+				from = pos & ~PAGE_CACHE_MASK;
+				zero_user_segments(page, 0, from,
+						from + copied, PAGE_CACHE_SIZE);
+			}
 		}
 		SetPageUptodate(page);
 	}
-- 
1.8.4

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