netdev - RE: [RFC PATCH v2 14/14] samples/bpf: sample application for AF

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Date:   Thu, 12 Apr 2018 11:08:05 +0000
From:   "Karlsson, Magnus" <magnus.karlsson@...el.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>,
        Björn Töpel <bjorn.topel@...il.com>
CC:     "Duyck, Alexander H" <alexander.h.duyck@...el.com>,
        "alexander.duyck@...il.com" <alexander.duyck@...il.com>,
        "john.fastabend@...il.com" <john.fastabend@...il.com>,
        "ast@...com" <ast@...com>,
        "willemdebruijn.kernel@...il.com" <willemdebruijn.kernel@...il.com>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "michael.lundkvist@...csson.com" <michael.lundkvist@...csson.com>,
        "Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
        "Singhai, Anjali" <anjali.singhai@...el.com>,
        "Zhang, Qi Z" <qi.z.zhang@...el.com>,
        "ravineet.singh@...csson.com" <ravineet.singh@...csson.com>,
        "Topel, Bjorn" <bjorn.topel@...el.com>
Subject: RE: [RFC PATCH v2 14/14] samples/bpf: sample application for AF_XDP
 sockets



> -----Original Message-----
> From: Jesper Dangaard Brouer [mailto:brouer@...hat.com]
> Sent: Thursday, April 12, 2018 1:05 PM
> To: Björn Töpel <bjorn.topel@...il.com>
> Cc: Karlsson, Magnus <magnus.karlsson@...el.com>; Duyck, Alexander H
> <alexander.h.duyck@...el.com>; alexander.duyck@...il.com;
> john.fastabend@...il.com; ast@...com;
> willemdebruijn.kernel@...il.com; daniel@...earbox.net;
> netdev@...r.kernel.org; michael.lundkvist@...csson.com; Brandeburg,
> Jesse <jesse.brandeburg@...el.com>; Singhai, Anjali
> <anjali.singhai@...el.com>; Zhang, Qi Z <qi.z.zhang@...el.com>;
> ravineet.singh@...csson.com; Topel, Bjorn <bjorn.topel@...el.com>;
> brouer@...hat.com
> Subject: Re: [RFC PATCH v2 14/14] samples/bpf: sample application for
> AF_XDP sockets
> 
> On Tue, 27 Mar 2018 18:59:19 +0200
> Björn Töpel <bjorn.topel@...il.com> wrote:
> 
> > +static void dump_stats(void)
> > +{
> > +	unsigned long stop_time = get_nsecs();
> > +	long dt = stop_time - start_time;
> > +	int i;
> > +
> > +	for (i = 0; i < num_socks; i++) {
> > +		double rx_pps = xsks[i]->rx_npkts * 1000000000.
> / dt;
> > +		double tx_pps = xsks[i]->tx_npkts * 1000000000.
> / dt;
> > +		char *fmt = "%-15s %'-11.0f %'-11lu\n";
> > +
> > +		printf("\n sock%d@", i);
> > +		print_benchmark(false);
> > +		printf("\n");
> > +
> > +		printf("%-15s %-11s %-11s %-11.2f\n", "", "pps",
> "pkts",
> > +		       dt / 1000000000.);
> > +		printf(fmt, "rx", rx_pps, xsks[i]->rx_npkts);
> > +		printf(fmt, "tx", tx_pps, xsks[i]->tx_npkts);
> > +	}
> > +}
> > +
> > +static void *poller(void *arg)
> > +{
> > +	(void)arg;
> > +	for (;;) {
> > +		sleep(1);
> > +		dump_stats();
> > +	}
> > +
> > +	return NULL;
> > +}
> 
> You are printing the "pps" (packets per sec) as an average over the entire
> test run... could you please change that to, at least also, have an more up-to-
> date value like between the last measurement?
> 
> The problem is that when you start the test, the first reading will be too low,
> and it takes time to average out/up. For ixgbe, first reading will be zero,
> because it does a link-down+up, which stops my pktgen.
> 
> The second annoyance is that I like to change system/kernel setting during
> the run, and observe the effect. E.g change CPU sleep states (via tuned-
> adm) during the test-run to see the effect, which I cannot with this long
> average.

Good points. Will fix.

/Magnus

> 
> --
> Best regards,
>   Jesper Dangaard Brouer
>   MSc.CS, Principal Kernel Engineer at Red Hat
>   LinkedIn: http://www.linkedin.com/in/brouer