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* [PATCH] libxfs: Optimize the loop for xfs_bitmap_empty
@ 2015-11-09 14:31 Jia He
  2015-11-10 12:54 ` Brian Foster
  0 siblings, 1 reply; 6+ messages in thread
From: Jia He @ 2015-11-09 14:31 UTC (permalink / raw)
  To: xfs; +Cc: Jia He, Brian Foster

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;
 	}
 
 	return (ret == 0);
-- 
2.5.0

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

^ permalink raw reply related	[flat|nested] 6+ messages in thread
* Re: [PATCH] libxfs: Optimize the loop for xfs_bitmap_empty
  2015-11-09 14:31 [PATCH] libxfs: Optimize the loop for xfs_bitmap_empty Jia He
@ 2015-11-10 12:54 ` Brian Foster
  2015-11-11  6:37   ` hejianet
  2015-11-11  7:49   ` [PATCH v2] " Jia He
  0 siblings, 2 replies; 6+ messages in thread
From: Brian Foster @ 2015-11-10 12:54 UTC (permalink / raw)
  To: Jia He; +Cc: xfs

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

^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH] libxfs: Optimize the loop for xfs_bitmap_empty
  2015-11-10 12:54 ` Brian Foster
@ 2015-11-11  6:37   ` hejianet
  2015-11-11  7:49   ` [PATCH v2] " Jia He
  1 sibling, 0 replies; 6+ messages in thread
From: hejianet @ 2015-11-11  6:37 UTC (permalink / raw)
  To: Brian Foster; +Cc: xfs


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
>>
>> _______________________________________________
>> 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
>

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

^ permalink raw reply	[flat|nested] 6+ messages in thread
* [PATCH v2] libxfs: Optimize the loop for xfs_bitmap_empty
  2015-11-10 12:54 ` Brian Foster
  2015-11-11  6:37   ` hejianet
@ 2015-11-11  7:49   ` Jia He
  2015-11-11 12:48     ` Brian Foster
  1 sibling, 1 reply; 6+ messages in thread
From: Jia He @ 2015-11-11  7:49 UTC (permalink / raw)
  To: xfs; +Cc: Jia He, Brian Foster

If there is any non zero bit in a long bitmap, it can jump out of the
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 | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_bit.c b/fs/xfs/libxfs/xfs_bit.c
index 0e8885a..0a94cce 100644
--- a/fs/xfs/libxfs/xfs_bit.c
+++ b/fs/xfs/libxfs/xfs_bit.c
@@ -32,13 +32,13 @@ int
 xfs_bitmap_empty(uint *map, uint size)
 {
 	uint i;
-	uint ret = 0;
 
 	for (i = 0; i < size; i++) {
-		ret |= map[i];
+		if (map[i] != 0)
+			return 0;
 	}
 
-	return (ret == 0);
+	return 1;
 }
 
 /*
-- 
2.5.0

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

^ permalink raw reply related	[flat|nested] 6+ messages in thread
* Re: [PATCH v2] libxfs: Optimize the loop for xfs_bitmap_empty
  2015-11-11  7:49   ` [PATCH v2] " Jia He
@ 2015-11-11 12:48     ` Brian Foster
  2015-12-16  3:04       ` hejianet
  0 siblings, 1 reply; 6+ messages in thread
From: Brian Foster @ 2015-11-11 12:48 UTC (permalink / raw)
  To: Jia He; +Cc: xfs

On Wed, Nov 11, 2015 at 03:49:01PM +0800, Jia He wrote:
> If there is any non zero bit in a long bitmap, it can jump out of the
> 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> 
> ---

Looks good to me:

Reviewed-by: Brian Foster <bfoster@redhat.com>

>  fs/xfs/libxfs/xfs_bit.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_bit.c b/fs/xfs/libxfs/xfs_bit.c
> index 0e8885a..0a94cce 100644
> --- a/fs/xfs/libxfs/xfs_bit.c
> +++ b/fs/xfs/libxfs/xfs_bit.c
> @@ -32,13 +32,13 @@ int
>  xfs_bitmap_empty(uint *map, uint size)
>  {
>  	uint i;
> -	uint ret = 0;
>  
>  	for (i = 0; i < size; i++) {
> -		ret |= map[i];
> +		if (map[i] != 0)
> +			return 0;
>  	}
>  
> -	return (ret == 0);
> +	return 1;
>  }
>  
>  /*
> -- 
> 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

^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH v2] libxfs: Optimize the loop for xfs_bitmap_empty
  2015-11-11 12:48     ` Brian Foster
@ 2015-12-16  3:04       ` hejianet
  0 siblings, 0 replies; 6+ messages in thread
From: hejianet @ 2015-12-16  3:04 UTC (permalink / raw)
  To: xfs, david; +Cc: Brian Foster

Hi David

Do you have any comments from your point of view? Thanks ;)

B.R.
Justin

在 11/11/15 8:48 PM, Brian Foster 写道:
> On Wed, Nov 11, 2015 at 03:49:01PM +0800, Jia He wrote:
>> If there is any non zero bit in a long bitmap, it can jump out of the
>> 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>
>> ---
> Looks good to me:
>
> Reviewed-by: Brian Foster <bfoster@redhat.com>
>
>>   fs/xfs/libxfs/xfs_bit.c | 6 +++---
>>   1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/xfs/libxfs/xfs_bit.c b/fs/xfs/libxfs/xfs_bit.c
>> index 0e8885a..0a94cce 100644
>> --- a/fs/xfs/libxfs/xfs_bit.c
>> +++ b/fs/xfs/libxfs/xfs_bit.c
>> @@ -32,13 +32,13 @@ int
>>   xfs_bitmap_empty(uint *map, uint size)
>>   {
>>   	uint i;
>> -	uint ret = 0;
>>   
>>   	for (i = 0; i < size; i++) {
>> -		ret |= map[i];
>> +		if (map[i] != 0)
>> +			return 0;
>>   	}
>>   
>> -	return (ret == 0);
>> +	return 1;
>>   }
>>   
>>   /*
>> -- 
>> 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
>

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

^ permalink raw reply	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2015-12-16  3:05 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2015-11-09 14:31 [PATCH] libxfs: Optimize the loop for xfs_bitmap_empty Jia He
2015-11-10 12:54 ` Brian Foster
2015-11-11  6:37   ` hejianet
2015-11-11  7:49   ` [PATCH v2] " Jia He
2015-11-11 12:48     ` Brian Foster
2015-12-16  3:04       ` hejianet

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