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

[Chao Yu]

Hi, Kim:

> -----Original Message-----
> From: Jaegeuk Kim [mailto:jaegeuk.kim@xxxxxxxxxxx]
> Sent: Tuesday, October 22, 2013 8:24 PM
> To: Chao Yu
> Cc: linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx; linux-fsdevel@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; èå
> Subject: Re: [f2fs-dev] [PATCH] f2fs: check all ones or zeros bitmap with integer
> data type for better mount performance
> 
> Hi,
> 
> 2013-10-22 (í), 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@xxxxxxxxxxx>
> > Signed-off-by: Yu Chao <chao2.yu@xxxxxxxxxxx>
> > ---
> >  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.

> 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?

> 
> > +			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

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