RE: [f2fs-dev] [PATCH] f2fs: check all ones or zeros bitmap with integer data type for better mount performance

[Jaegeuk Kim <jaegeuk.kim@samsung.com>]

Hi,

2013-10-23 (수), 11:23 +0800, Chao Yu:
> Hi, Kim:
> 
> > -----Original Message-----
> > From: Jaegeuk Kim [mailto:jaegeuk.kim@samsung.com]
> > Sent: Tuesday, October 22, 2013 8:24 PM
> > To: Chao Yu
> > Cc: linux-f2fs-devel@lists.sourceforge.net; linux-fsdevel@vger.kernel.org;
> > linux-kernel@vger.kernel.org; 谭姝
> > Subject: Re: [f2fs-dev] [PATCH] f2fs: check all ones or zeros bitmap with integer
> > data type for better mount performance
> > 
> > Hi,
> > 
> > 2013-10-22 (화), 17:28 +0800, Chao Yu:
> > > 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.
> > >
> > > Signed-off-by: Tan Shu <shu.tan@samsung.com>
> > > Signed-off-by: Yu Chao <chao2.yu@samsung.com>
> > > ---
> > >  fs/f2fs/segment.h |   13 +++++++++++++
> > >  1 file changed, 13 insertions(+)
> > >
> > > diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h index
> > > 7f94d78..d43ab9f 100644
> > > --- a/fs/f2fs/segment.h
> > > +++ b/fs/f2fs/segment.h
> > > @@ -543,6 +543,7 @@ 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;
> > > +	int *valid_map = (int *)raw_sit->valid_map;
> > >  	int valid_blocks = 0;
> > >  	int i;
> > >
> > > @@ -552,6 +553,19 @@ 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) {
> > > +		for (i = 0; i < SIT_VBLOCK_MAP_SIZE / sizeof(int); i++)
> > 
> > We cannot guarantee all the time that SIT_VBLOCK_MAP_SIZE is multiple of
> > sizeof(int).
> Well, It's really large changes for f2fs if SIT_VBLOCK_MAP_SIZE value is being modified.

But, it can be changed.
Please do not add any unnecessary assumption.

> 
> > How about using memcmp() with __u8?
> Do you mean that we can alloc all zeros or ones memory in SIT_VBLOCK_MAP_SIZE size,
> then memcmp() it with sit bitmap by __u8?

Yap.
Ah, but there is another one.
It would be better to use find_next_bit_le() and
find_next_zero_bit_le().
Any idea?

> 
> > 
> > > +			if (unlikely(valid_map[i] != 0))
> > > +				BUG();
> > > +		return;
> > > +	} else if (GET_SIT_VBLOCKS(raw_sit) == sbi->blocks_per_seg) {
> > > +		for (i = 0; i < SIT_VBLOCK_MAP_SIZE / sizeof(int); i++)
> > > +			if (unlikely(valid_map[i] != -1))
> > > +				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))
> > > ---
> > >
> > > --
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> > 
> > --
> > Jaegeuk Kim
> > Samsung
> 

-- 
Jaegeuk Kim
Samsung