On Wed, Oct 7, 2009 at 2:01 PM, Lasher, Donn <[email protected]>wrote:
> -----Original Message----- > From: Pete Templin [mailto:[email protected]] > Subject: Re: [c-nsp] GSR CPU Process is very HIGH 95% > > Lasher, Donn wrote: > > >> To clarify, this depends on both the card type (engine 0/1/2/3/4/5) > and > >> traffic type (mpls, DSCP marking, etc). You can be doing everything > >> right, and still have 50% CPU with the wrong combination of those > two.. > >> (For example, MPLS Labeling and Engine0 GIG-E card at 100M of > traffic) > > >Right, but that'd be 50% CPU on the linecard, not on the xRP, right? > > > >(In other words, you'd find 50% CPU by doing 'execute-on all sh proc c > s > >| e 0.0.%' but wouldn't find it by doing 'sh proc c s | e 0.0.%'.) > > No, in the example I gave, 100M of CE-PE MPLS traffic (IE the router is > labeling/unlabeling) on an Engine0 1-port GIG-E line card will run the > Processor CPU up nice and high. *That is because an Eng 0 LC switches traffic in software i.e. the LC CPU does each and every lookup off the LC FIB table ( a rather CPU intensive activity - at....you guessed it, LC CPU "interrupt level") - which was downloaded as normal from the RP FIB table. (GSR Architecture in four bullet points) The GSR (and most distributed platforms are designed as follows... * - *RP takes care of coalescing routes, creating FIB tables and all other housekeeping activities.* - *RP pushes FIB table down to all LCs and IOS 'inconsistency checker' runs every so often to ensure the 'consistency' of RP and LC copies of FIB tables et al. * - *If LC has hardware switching capabilities (i.e. > Eng 1)...yipppe. It switches packets in HW (ASIC) or else...* - *It switches in software i.e. LC CPU 'manually' does the CEF table lookup for each and every packet header - very CPU intensive. However, if, for some strange reason, a route doesn't exists on LC CEF table, the LC will punt to RP CPU. And RP will the final say on what happens to the packet. * ** Eninja _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
