Re: [Lse-tech] Re: (RFC): SKB Initialization

["Mala Anand" <manand@us.ibm.com>]

Dave Hansen wrote..
>Mala Anand wrote:
>> The third scope would be measuring this patch in a workload environment.
>> We measured it in a web serving workload and found that we get 0.7%
>> improvement.

>First of all, the patch doesn't apply at all against the current
>bitkeeper tree.  I can post the exact one I used if you like.

>I tried this under our Specweb99 setup.  Here's a snippet of
>readprofile with, then without the patch:

>alloc:free ratio: 1.226
>(__kfree_skb+alloc_skb)/total = 3.14%


>alloc:free ratio: 0.348
>(__kfree_skb+alloc_skb)/total = 2.79%

>You can see the entire readprofile here:
>http://www.sr71.net/~specweb99/run-specweb-100sec-2400-2.5.31-bk+4-kmap-08-22-2002-11.20.17/

>http://www.sr71.net/~specweb99/run-specweb-100sec-2400-2.5.31-bk+4-kmap-mala-08-22-2002-11.44.25/

>No, I don't know why I have so much idle time.

Readprofile ticks are not as accurate as the cycles I measured.
Moreover readprofile can give misleading information as it profiles
on timer interrupts. The alloc_skb and __kfree_skb call memory
management routines and interrupts are disabled in many parts of that code.
So I don't trust the readprofile data.



Regards,
    Mala


   Mala Anand
   IBM Linux Technology Center - Kernel Performance
   E-mail:manand@us.ibm.com
   http://www-124.ibm.com/developerworks/opensource/linuxperf
   http://www-124.ibm.com/developerworks/projects/linuxperf
   Phone:838-8088; Tie-line:678-8088