RE: [f2fs-dev] [PATCH V2 RESEND] f2fs: check all ones or zeros bitmapwith bitops for better mount performance

[Changman Lee]

Review attached patch, please.

-----Original Message-----
From: Chao Yu [mailto:chao2.yu@xxxxxxxxxxx] 
Sent: Tuesday, October 29, 2013 3:51 PM
To: jaegeuk.kim@xxxxxxxxxxx
Cc: linux-fsdevel@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx
Subject: [f2fs-dev] [PATCH V2 RESEND] f2fs: check all ones or zeros bitmap
with bitops for better mount performance

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@xxxxxxxxxxx>
Signed-off-by: Shu Tan <shu.tan@xxxxxxxxxxx>
Signed-off-by: Chao Yu <chao2.yu@xxxxxxxxxxx>
---
 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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