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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 23:28:03 +0800
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <52EBBC3D.5030507@xxxxxxxxxxx>
References: <52EBAF91.10608@xxxxxxxxxx> <52EBBC3D.5030507@xxxxxxxxxxx>
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0
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...
Otherwise, maybe some like find_first_bit(map, size) would be
more convenient.

Thanks,
-Jeff

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