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

[Chao Yu <chao2.yu@samsung.com>]

Hi Gu,

> -----Original Message-----
> From: Gu Zheng [mailto:guz.fnst@cn.fujitsu.com]
> Sent: Thursday, October 24, 2013 6:04 PM
> To: Chao Yu
> Cc: jaegeuk.kim@samsung.com; linux-fsdevel@vger.kernel.org;
> linux-kernel@vger.kernel.org; linux-f2fs-devel@lists.sourceforge.net; '谭姝'
> Subject: Re: [f2fs-dev] [PATCH V2] f2fs: check all ones or zeros bitmap with
> bitops for better mount performance
> 
> Hi Yu,
> On 10/24/2013 04:21 PM, Chao Yu wrote:
> 
> > 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.
> >
> > v2:
> >     use find_next_bit_le/find_next_zero_bit_le for better performance and
> readable as Jaegeuk suggested.
> 
> If so, how about using find_first_{zero_}bit_le instead? It's more neat.
It seems more neat. I will take it, thanks.

> 
> Regards,
> Gu
> 
> >
> > Suggested-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
> > Signed-off-by: Tan Shu <shu.tan@samsung.com>
> > Signed-off-by: Yu Chao <chao2.yu@samsung.com>
> > ---
> >  fs/f2fs/segment.h |   17 +++++++++++++++++
> >  1 file changed, 17 insertions(+)
> >
> > diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h index
> > 7f94d78..d25b6af 100644
> > --- a/fs/f2fs/segment.h
> > +++ b/fs/f2fs/segment.h
> > @@ -552,6 +552,23 @@ static inline void check_block_count(struct
> f2fs_sb_info *sbi,
> >  	/* check boundary of a given segment number */
> >  	BUG_ON(segno > end_segno);
> >
> > +	/* check all ones or zeros valid_map */
> > +	if (GET_SIT_VBLOCKS(raw_sit) == 0) {
> > +		int pos = find_next_bit_le(&raw_sit->valid_map,
> > +					sbi->blocks_per_seg,
> > +					0);
> > +		if (pos != sbi->blocks_per_seg)
> > +			BUG();
> > +		return;
> > +	} else if (GET_SIT_VBLOCKS(raw_sit) == sbi->blocks_per_seg) {
> > +		int pos = find_next_zero_bit_le(&raw_sit->valid_map,
> > +					sbi->blocks_per_seg,
> > +					0);
> > +		if (pos != sbi->blocks_per_seg)
> > +			BUG();
> > +		return;
> > +	}
> > +
> >  	/* check bitmap with valid block count */
> >  	for (i = 0; i < sbi->blocks_per_seg; i++)
> >  		if (f2fs_test_bit(i, raw_sit->valid_map))