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

From: Mala Anand (
Date: Fri Aug 23 2002 - 09:44:23 EST

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:


>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.


   Mala Anand
   IBM Linux Technology Center - Kernel Performance
   Phone:838-8088; Tie-line:678-8088

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