In dispatch_node, before we call node->function any accumulated clock cycles are counted toward idle, after the node->function returns if ( (VLIB_NODE_TYPE_PRE_INPUT || VLIB_NODE_TYPE_INPUT) && number of packets processed == 0) then we count it as idle, else we count it as busy.
From: Ramkumar B <ramukmar1...@gmail.com> Sent: Wednesday, December 16, 2020 10:27 AM To: bjerem...@gmail.com Cc: vpp-dev@lists.fd.io Subject: Re: [vpp-dev] Core Load Calculation The processing of the rx queue is counted toward IDLE Please explain what kind of processing. We are not doing any such rx processing separately. For us, the ring_dequeue_burst's cycles is negligible compared to processing cycles. On Wed, Dec 16, 2020 at 8:54 PM <bjerem...@gmail.com <mailto:bjerem...@gmail.com> > wrote: Nope… the math works out… nothing goes to 0… we are incrementing both IDLE and BUSY. The processing of the rx queue is counted toward IDLE… In a completely idle system, the cpu usage falls to 0… as traffic ramps up it will go further positive based on pps, and as it goes to idle again it will go down to 0… From: Damjan Marion <dmar...@me.com <mailto:dmar...@me.com> > Sent: Wednesday, December 16, 2020 3:00 AM To: bjerem...@gmail.com <mailto:bjerem...@gmail.com> Cc: Nick Zavaritsky <nick.zavarit...@emnify.com <mailto:nick.zavarit...@emnify.com> >; ramukmar1...@gmail.com <mailto:ramukmar1...@gmail.com> ; vpp-dev@lists.fd.io <mailto:vpp-dev@lists.fd.io> Subject: Re: [vpp-dev] Core Load Calculation On 16.12.2020., at 05:45, bjerem...@gmail.com <mailto:bjerem...@gmail.com> wrote: What we did was to count clock cycles (timestamps) spent processing the nodes, call this busy, and count the clock cycles spent elsewhere, call this idle. And then simply output (busy/(busy + idle). We did this per thread and stored the calculations globally. We then outputted the calculations on the ‘vppctl show thread’ cli. This doesnt make lot of sense. Each input node is spending cycles to process rx queue, and out of that processing there may be zero or non-zero packets. So in completelly idle system according to your math result will be far away from 0. This created a nice cpu usage metric that seems pretty accurate for io and worker threads… What do you mean by io threads? We compared this to something like htop for the worker threads and its within ~1%, the io cores seem the same as we can see the usage go to about 80-90% when we start dropping packets. We are able to calculate the approx. PPS for a given system configuration. It actually wasn’t a lot of effort. I think only three files were touched. 1. A new header file o create the global data structure to hold the clock cycle counts and associated macros to init and update the structures. 2. Vlib/main.c to instrument the main loop and collect the busy/idle clock cycles 3. Vlib threads_cli.c as show threads fn was used to output the cpu usage per thread. From: vpp-dev@lists.fd.io <mailto:vpp-dev@lists.fd.io> <vpp-dev@lists.fd.io <mailto:vpp-dev@lists.fd.io> > On Behalf Of Nick Zavaritsky Sent: Tuesday, December 15, 2020 1:38 PM To: ramukmar1...@gmail.com <mailto:ramukmar1...@gmail.com> Cc: vpp-dev@lists.fd.io <mailto:vpp-dev@lists.fd.io> Subject: Re: [vpp-dev] Core Load Calculation We’ve been using flamegraphs quite successfully to see how much leeway is there. Ex: https://gist.githack.com/mejedi/d5d094df63faba66d413a677fcef26e3/raw/95294d36c4b180ba6741d793bf345041b00af48e/g.svg On 15 Dec 2020, at 19:53, Ramkumar B via lists.fd.io <http://lists.fd.io/> <ramukmar1998=gmail....@lists.fd.io <mailto:ramukmar1998=gmail....@lists.fd.io> > wrote: Hello All, I'm trying to calculate VPP core's load. I completely understand about the polling cores' 100% CPU usage. My requirement is different where I need to calculate the core's load based on how much more PPS it can handle before a packet drop occurs in the queue. The vec/call is a good indicator of load, but it does not increase linearly with PPS. This is because of the VPP's self balancing behaviour where the cost per packet reduces as load increases. It would be a great help if anyone can point out factors to calculate load. Thanks and regards, Ramkumar Balu
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