Re: [PATCH] libxfs: Optimize the loop for xfs_bitmap_empty

[Brian Foster <bfoster@redhat.com>]

On Mon, Nov 09, 2015 at 10:31:22PM +0800, Jia He wrote:
> If there is any non zero bit in a long bitmap, it can jump out of the for 
> loop and finish the function as soon as possible.
> 
> Signed-off-by: Jia He <hejianet@gmail.com>
> Cc: Dave Chinner <david@fromorbit.com> 
> Cc: Brian Foster <bfoster@redhat.com> 
> ---
>  fs/xfs/libxfs/xfs_bit.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/xfs/libxfs/xfs_bit.c b/fs/xfs/libxfs/xfs_bit.c
> index 0e8885a..84614b0 100644
> --- a/fs/xfs/libxfs/xfs_bit.c
> +++ b/fs/xfs/libxfs/xfs_bit.c
> @@ -36,6 +36,8 @@ xfs_bitmap_empty(uint *map, uint size)
>  
>  	for (i = 0; i < size; i++) {
>  		ret |= map[i];
> +		if (ret != 0)
> +			return 0;
>  	}
>  

Seems Ok to me, but if we're going to do this, why not just kill ret
entirely? For example, check 'if (map[i] != 0) return 0;' in the loop
and unconditionally return 1 if we make it to the end.

Brian

>  	return (ret == 0);
> -- 
> 2.5.0
> 
> _______________________________________________
> xfs mailing list
> xfs@oss.sgi.com
> http://oss.sgi.com/mailman/listinfo/xfs

_______________________________________________
xfs mailing list
xfs@oss.sgi.com
http://oss.sgi.com/mailman/listinfo/xfs