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Re: [PATCH] xfs: improve xfs_bitmap_empty()

To: Eric Sandeen <sandeen@xxxxxxxxxxx>, "xfs@xxxxxxxxxxx" <xfs@xxxxxxxxxxx>
Subject: Re: [PATCH] xfs: improve xfs_bitmap_empty()
From: Jeff Liu <jeff.liu@xxxxxxxxxx>
Date: Fri, 31 Jan 2014 23:51:23 +0800
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <52EBC1AF.6020000@xxxxxxxxxxx>
References: <52EBAF91.10608@xxxxxxxxxx> <52EBBC3D.5030507@xxxxxxxxxxx> <52EBC103.5050006@xxxxxxxxxx> <52EBC1AF.6020000@xxxxxxxxxxx>
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0
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@xxxxxxxxxx>
>>>>
>>>> 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@xxxxxxxxxx>
>>>
>>> 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@xxxxxxxxxx>
>>>
>>> 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.

Thanks,
-Jeff

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