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

Jamal wrote ..

On Mon, 26 Aug 2002, Mala Anand wrote:

quoted

Troy Wilson (who works with me) posted SPECweb99 results using my
skbinit patch to lkml on Friday:
 http://www.uwsg.iu.edu/hypermail/linux/kernel/0208.2/1470.html
I know you don't subscribe to lkml. Have you seen these results?
On Numa machine it showed around 3% improvement using SPECweb99.

The posting you pointed to says 1% - not that it matters. It becomes more
insignificant when skb recycling comes in play mostly because the alloc
and freeing of skbs doesnt really show up as hotlist item within
the profile.
I am not saying it is totaly useless -- anything that will save a few
cycles is good;

SPECweb99 profile shows that __kfree_skb is in the top 5 hot routines. We
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. I think this patch is pretty safe and I anticipate greater gains
on NUMA systems.

BTW the 3% gain that I reported earlier on NUMA is done at another site
of IBM and it turned out to be it is not a NUMA machine. It is also
an 8-way SMP machine, however those are non-complaint SPECWeb99 runs so
I won't be able to use those results.

The alloc and free routines are not hot in netperf3 profiles. However
I am seeing some gains there also, not significant. I will post netperf3
results with skbinit patch later.



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

On Tue, 27 Aug 2002, Mala Anand wrote:

SPECweb99 profile shows that __kfree_skb is in the top 5 hot routines. We
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 wouldnt write
my mother to tell her about it.

cheers,
jamal