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

On Tue, 27 Aug 2002, Mala Anand wrote:

quoted

SPECweb99 profile shows that __kfree_skb is in the top 5 hot routines.

We

quoted

will test the skb recycle patch on SPECweb99 and add skbinit patch
to that and see how it helps.  What I understand is that the skb recycle
patch does not attempt to recycle if the skbs are allocated on CPU
and freed on another CPU. Is that right? If so, skbinit patch will help
those cases.

yes it will. Not significant is my current thinking. i.e i wouldn't write
my mother to tell her about it.

I have not looked at Robert's recycle skb patch yet. I couldn't
find it in the link he sent me so I don't know how it works. However
I thought about it a little more and realized that even when you
recycle the skbs, they need to be initialized (cleaned up). I don't
understand how
can the recycle skb patch avoid calling constructors and destructors for
the
skb.  The skbs are given back to the driver instead of freeing to the skb
hot list
or to the slab. That does not eliminate the part of the code of kfree_skb
which
releases dst, initializes part of skb and executes destructor.
Tell me if I am wrong but wouldn't it break the code. So I do think that
recycle skb patch will not mitigate the benefits of the skb init
patch.


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