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

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Message-id: <002301ced48e$c615e010$5241a030$@samsung.com>
Date:	Tue, 29 Oct 2013 18:06:48 +0800
From:	Chao Yu <chao2.yu@...sung.com>
To:	'Changman Lee' <cm224.lee@...sung.com>, jaegeuk.kim@...sung.com
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net
Subject: RE: [f2fs-dev] [PATCH V2 RESEND] f2fs: check all ones or zeros bitmap
 with bitops for better mount performance

Hi Lee,

It's a good point.

Firstly, In your patch:
	/* 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++;
+		valid_blocks += bit_count_byte(raw_sit->valid_map[i]);
+
 	BUG_ON(GET_SIT_VBLOCKS(raw_sit) != valid_blocks);
 }

for (i = 0; i < sbi->blocks_per_seg; i++)
should be replace with
for (i = 0; i < SIT_VBLOCK_MAP_SIZE; i++)

Secondly, I tested your patch and mine
with SD and emmc with all zeros bitmap.
It shows my patch takes litter time.
Could you test and compare the performance of two patches.

-- 
1.7.10.4


> -----Original Message-----
> From: Changman Lee [mailto:cm224.lee@...sung.com]
> Sent: Tuesday, October 29, 2013 3:36 PM
> To: 'Chao Yu'; jaegeuk.kim@...sung.com
> Cc: linux-fsdevel@...r.kernel.org; linux-kernel@...r.kernel.org;
> linux-f2fs-devel@...ts.sourceforge.net
> Subject: RE: [f2fs-dev] [PATCH V2 RESEND] f2fs: check all ones or zeros
bitmap
> with bitops for better mount performance
> 
> Review attached patch, please.
> 
> -----Original Message-----
> From: Chao Yu [mailto:chao2.yu@...sung.com]
> Sent: Tuesday, October 29, 2013 3:51 PM
> To: jaegeuk.kim@...sung.com
> Cc: linux-fsdevel@...r.kernel.org; linux-kernel@...r.kernel.org;
> linux-f2fs-devel@...ts.sourceforge.net
> 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@...sung.com>
> Signed-off-by: Shu Tan <shu.tan@...sung.com>
> Signed-off-by: Chao Yu <chao2.yu@...sung.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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