netdev - RE: Question on "net: allocate skbs on local node"

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Date:	Thu, 07 Apr 2011 07:16:52 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Wei Gu <wei.gu@...csson.com>
Cc:	netdev <netdev@...r.kernel.org>,
	Alexander Duyck <alexander.h.duyck@...el.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: RE: Question on "net: allocate skbs on local node"

Le jeudi 07 avril 2011 à 06:58 +0200, Eric Dumazet a écrit :
> Le jeudi 07 avril 2011 à 10:16 +0800, Wei Gu a écrit :
> > Hi Eric,
> > Testing with ixgbe Linux 2.6.38 driver:
> > We have a little better thruput figure with this driver, but it looks
> > not scalling at all, I always stressed one CPU core/24.
> > And when look the perf report for ksoftirqd/24, the most cost function
> > is still "_raw_spin_unlock_irqstore" and the IRQ/s is huge, it's
> > somehow conflicts with desgin of NAPI. On linux 2.6.32 while the CPU
> > was stressed the IRQ will descreased while the NAPI will running much
> > on the polling mode. I don't know why on 2.6.38 the IRQ was keep
> > increasing.
> 
> 
> CC netdev and Intel guys, since they said it should not happen (TM)
> 
> IF you dont use DCA (make sure ioatdma module is not loaded), how comes
> alloc_iova() is called at all ?
> 
> IF you use DCA, how comes its called, since the same CPU serves a given
> interrupt ?
> 
> 

But then, maybe you forgot to cpu affine IRQS ?

High performance routing setup is tricky, since you probably want to
disable many features that are ON by default : Most machines act as a
end host.



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