2002-08-21 18:05:53

by Mala Anand

[permalink] [raw]
Subject: Re: (RFC): SKB Initialization


>On Wed, Aug 21, 2002 at 11:59:44AM -0500, Mala Anand wrote:
>> The patch reduces the numer of cylces by 25%

>The data you are reporting is flawed: where are the average cycle
>times spent in __kfree_skb with the patch?

I measured the cycles for only the initialization code in alloc_skb
and __kfree_skb. Since the init code is removed from __kfree_skb,
no cycles are spent there.



Regards,
Mala


Mala Anand
IBM Linux Technology Center - Kernel Performance
E-mail:[email protected]
http://www-124.ibm.comdeveloperworks/opensource/linuxperf
http://www-124.ibm.com/developerworks/projects/linuxperf
Phone:838-8088; Tie-line:678-8088





2002-08-21 18:11:55

by Benjamin LaHaise

[permalink] [raw]
Subject: Re: (RFC): SKB Initialization

On Wed, Aug 21, 2002 at 01:07:09PM -0500, Mala Anand wrote:
>
> >On Wed, Aug 21, 2002 at 11:59:44AM -0500, Mala Anand wrote:
> >> The patch reduces the numer of cylces by 25%
>
> >The data you are reporting is flawed: where are the average cycle
> >times spent in __kfree_skb with the patch?
>
> I measured the cycles for only the initialization code in alloc_skb
> and __kfree_skb. Since the init code is removed from __kfree_skb,
> no cycles are spent there.

Then the testing technique is flawed. You should include all of the
operations included in an alloc_skb/kfree_skb pair in order to see
the overall effect of the change, otherwise your change could have a
net negative effect which would not be noticed.

-ben
--
"You will be reincarnated as a toad; and you will be much happier."