Thanks Dave for the feedback. I will give a look at 19.04 and master/latest.
Regards -Prashant On Mon, Jun 10, 2019 at 5:11 PM Dave Barach (dbarach) <dbar...@cisco.com> wrote: > > We've added purpose-built callback hooks in the main dispatch loop [in > master/latest] so that folks can hook up whatever sort of instrumentation > they like. Please have a look at that scheme. > > There's no point in attempting to upstream your work to stable/1801. We long > since shut down the CSIT performance jobs for 18.01, and we will not merge > feature patches into stable/1801. > > Many things have changed since 18.01 - thousands of patches' worth, including > significant performance tunes and a new build system - IIWY I'd rebase to > 19.04 and/or master/latest. > > HTH... Dave > > -----Original Message----- > From: vpp-dev@lists.fd.io <vpp-dev@lists.fd.io> On Behalf Of Prashant > Upadhyaya > Sent: Monday, June 10, 2019 6:13 AM > To: Dave Barach (dbarach) <dbar...@cisco.com> > Cc: vpp-dev@lists.fd.io > Subject: Re: [vpp-dev] Approximate effective CPU utilization of VPP worker > > Hi Dave, > > Thanks for your suggestion. > > As an attempt towards an alternate strategy, I did go ahead and make a change > in the main loop of VPP18.01 (similar change as I describe below should be > valid much in a similar fashion to subsequent > releases) and it seems to be working for me, but there might be many catches > so I am disclosing what I did below. > > In vlib_main_or_worker_loop, on a per thread basis, I accumulated time in the > following areas :- . vl_api_send_pending_rpc_requests (if there were indeed > some pending) . dispatch_node (if the node's callback returned n > 0) . > vlib_frame_queue_dequeue (again if return value was > 0) The above acted as a > numerator for a sampling time of 1 second, the denominator. At the stroke of > this window, I divide, store result and clear all accumulations to begin > afresh. > The calculations are valid only for worker threads as I don't care for main > thread whose cpu is reported by linux anyway. > > Empirically it seems to work ok for me. I did check by making my own plugins > quite busy and so forth. > > Do you think, the above is a reasonable custom strategy or is there a chance > of destroying performance of main loop (and thus the whole > system) due to frequent calls to vlib_time_now, would appreciate if you can > give your opinion. > > Regards > -Prashant > > > > > > On Fri, Jun 7, 2019 at 5:22 PM Dave Barach (dbarach) <dbar...@cisco.com> > wrote: > > > > The instantaneous vector size - in the stats segment, per-thread - is the > > best measure of how hard vpp is working. > > > > > > > > It's not a linear function of the offered load, but for any given offered > > load / feature set you can model it with three segments: > > > > > > > > Dead asleep: vector size < 3, offered load up to maybe 1 mpps’ worth > > of simple forwarding Linear region: vector size increases smoothly as > > offered load increases, up a vector size of maybe 128 or so Hit the wall: a > > slight increate in offered load causes a huge jump in the vector size, > > traffic loss, etc. > > > > > > > > HTH... Dave > > > > > > > > -----Original Message----- > > From: vpp-dev@lists.fd.io <vpp-dev@lists.fd.io> On Behalf Of Prashant > > Upadhyaya > > Sent: Friday, June 7, 2019 5:41 AM > > To: vpp-dev@lists.fd.io > > Subject: [vpp-dev] Approximate effective CPU utilization of VPP worker > > > > > > > > Hi, > > > > > > > > I understand that VPP workers poll so they are always at 100 % CPU. > > > > However, I want to get an estimate of what is the effective CPU utilization > > i.e. the amount which was spent in doing the work for packet processing. > > > > > > > > In the native applications, the crude way I used to employ was to take a > > time window of say 1 second and I already know how many cpu cycles it is > > worth, this acted as the denominator. Then in every packet poll, I used to > > count the cycles spent when the packet was actually brought in and > > processed. So empty polls were not counted in the used cycles. > > > > This acted like the numerator. When the window was exhausted, I used the > > numerator/denominator to get an approximation of effective CPU utilization > > of the worker. > > > > > > > > Is something like this already possible in VPP, I need to constantly > > monitor the effective CPU utilization of the worker at runtime to take some > > decisions and inform the system peers eg. to reduce sending traffic etc. > > > > > > > > Regards > > > > -Prashant
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