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

[hejianet <hejianet@gmail.com>]

Hi Brian
Thanks, I will resend the patch V2

B.R.
Justin

在 11/10/15 8:54 PM, Brian Foster 写道:
> 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
>>
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