From: Chao Yu <chao2.yu@samsung.com>
To: jaegeuk.kim@samsung.com
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net,
        =?utf-8?B?J+iwreWnnSc=?= <shu.tan@samsung.com>
Subject: [f2fs-dev] [PATCH V2 RESEND] f2fs: check all ones or zeros bitmap with
 bitops for better mount performance
Date: Tue, 29 Oct 2013 14:50:40 +0800
Message-id: <001f01ced473$4c5cc9c0$e5165d40$@samsung.com>
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Previously, check_block_count check valid_map with bit data type in common scenario that sit has all ones or zeros bitmap, it makes low mount performance.
So let's check the special bitmap with integer data type instead of the bit one.

v1-->v2:
    use find_next_{zero_}bit_le for better performance and readable as Jaegeuk suggested.
	use neat logogram in comment as Gu Zheng suggested.
	search continuous ones or zeros for better performance when checking mixed bitmap.

Suggested-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
Signed-off-by: Shu Tan <shu.tan@samsung.com>
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
---
 fs/f2fs/segment.h |   19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index abe7094..a7abfa8 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -550,8 +550,9 @@ static inline void check_block_count(struct f2fs_sb_info *sbi,
 {
 	struct f2fs_sm_info *sm_info = SM_I(sbi);
 	unsigned int end_segno = sm_info->segment_count - 1;
+	bool is_valid  = test_bit_le(0, raw_sit->valid_map) ? true : false;
 	int valid_blocks = 0;
-	int i;
+	int cur_pos = 0, next_pos;
 
 	/* check segment usage */
 	BUG_ON(GET_SIT_VBLOCKS(raw_sit) > sbi->blocks_per_seg);
@@ -560,9 +561,19 @@ static inline void check_block_count(struct f2fs_sb_info *sbi,
 	BUG_ON(segno > end_segno);
 
 	/* check bitmap with valid block count */
-	for (i = 0; i < sbi->blocks_per_seg; i++)
-		if (f2fs_test_bit(i, raw_sit->valid_map))
-			valid_blocks++;
+	do {
+		if (is_valid) {
+			next_pos = find_next_zero_bit_le(&raw_sit->valid_map,
+					sbi->blocks_per_seg,
+					cur_pos);
+			valid_blocks += next_pos - cur_pos;
+		} else
+			next_pos = find_next_bit_le(&raw_sit->valid_map,
+					sbi->blocks_per_seg,
+					cur_pos);
+		cur_pos = next_pos;
+		is_valid = !is_valid;
+	} while (cur_pos < sbi->blocks_per_seg);
 	BUG_ON(GET_SIT_VBLOCKS(raw_sit) != valid_blocks);
 }
 
-- 
1.7.9.5

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