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Date: Fri, 31 Jan 2014 10:28:02 -0600
From: Mark Tinguely <tinguely@sgi.com>
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Subject: Re: [PATCH] xfs: improve xfs_bitmap_empty()
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To: Jeff Liu <jeff.liu@oracle.com>
Cc: Eric Sandeen <sandeen@sandeen.net>, "xfs@oss.sgi.com" <xfs@oss.sgi.com>

On 01/31/14 09:51, Jeff Liu wrote:
>
> On 01/31 2014 23:30 PM, Eric Sandeen wrote:
>> On 1/31/14, 9:28 AM, Jeff Liu wrote:
>>>
>>> On 01/31 2014 23:07 PM, Eric Sandeen wrote:
>>>> On 1/31/14, 8:13 AM, Jeff Liu wrote:
>>>>> From: Jie Liu<jeff.liu@oracle.com>
>>>>>
>>>>> There is no need to travel through the whole bitmap items to verify
>>>>> if the bitmap array is empty or not, instead, just return 0 directly
>>>>> if an item is detected in bitmap array.
>>>>>
>>>>> Signed-off-by: Jie Liu<jeff.liu@oracle.com>
>>>>
>>>> Makes sense (and the long loop was my fault, I guess, but it's
>>>> better than it was, see commit 24ad33f!)
>>>
>>> Ah, you have killed a lots code there! :)
>>>> Reviewed-by: Eric Sandeen<sandeen@redhat.com>
>>>>
>>>> I wonder if something like:
>>>>
>>>> return (find_first_set(map, size) == size);
>>>>
>>>> would be faster (or if it'd be worth it)...?
>>>> Probably not.  :)
>>>>
>>>
>>> Well, when I looking through our bitmap source, I once thought if
>>> we can replace the current code with the generic bitmap library.
>>> However, our map is uint rather than unsigned long...
>>
>> Technically the unsigned long (pointer) is just the bitmap address,
>> I think.
>
> Yeah, so this might worth to try on long terms.
>

The blf_data_map[] is int aligned, not long aligned.
You could reflect the alignment difference in the offset or
change the alignment in the structure.

--Mark.

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