[c-nsp] NPE-G2: mixed interrupt/polling packet processing on POS interface

[Rodney Dunn]

For G2 vs G1 that's correct.

For ethernet vs. serial the performance from what I recall is less.

Rodney


On Thu, Feb 21, 2008 at 12:35:32PM +0100, Ultramajestic wrote:
> So as far as I understand, the performance is not degraded, isn't it?
> 
> 
> El mi??, 20-02-2008 a las 09:30 -0500, Rodney Dunn escribi??:
> > Philippe,
> > 
> > I need to check back with the BU on it. I thought they were putting
> > a document out on this G2 processing reporting issue.
> > 
> > Basically due to the way the G2 does CPU accounting it looks
> > like it's higher at lower loads based on the CPU measurements.
> > 
> > If you put it in the lab and measure NDR's the CPU can forward
> > much more than the G1 even though the G2 "shows" higher CPU
> > in the output.
> > 
> > That has confused a lot of folks and understandably so.
> > 
> > Rodney
> > 
> >  
> > 
> > On Wed, Feb 20, 2008 at 03:12:27PM +0100, Philippe Strauss wrote:
> > > Hello c-nsp,
> > > 
> > > We are running c7200 vxr with NPE-G2, but are seeing way to high CPU
> > > usage (85%) at only 225kPPS in+out.
> > > 
> > > It _seems_ it's due to the fact we're using a POS interface.
> > > I _guess_, the G2, when using GigE interface, is doing a mixed
> > > interrupt/polling mode for processing each packets.
> > > (like linux NAPI: above a certain PPS value, the driver switch
> > > from interrupt to polling mode). It's a guess.
> > > 
> > > But the CPU usage is for sure much lower when using only the 3 GigE
> > > embeded on the mainboard.
> > > 
> > > Keeping interrupt only processing for POS, which may be used
> > > to switch voice traffic, has some rational behind it.
> > > 
> > > But we're using it only to switch data/ip, and I'm wondering
> > > if there's a way to lower the CPU usage despite using POS?
> > > 
> > > like a switch to enable mixed interrupt/polling driver on the POS?
> > > 
> > > would be highly helpfull.
> > > 
> > > regards.
> > > 
> > > -- 
> > > Philippe Strauss
> > > av. de Beaulieu 25
> > > 1004 Lausanne
> > > http://philou.ch
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