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Message-ID: <20140916175600.018350fe@redhat.com> Date: Tue, 16 Sep 2014 17:56:00 +0200 From: Jesper Dangaard Brouer <brouer@...hat.com> To: Eric Dumazet <eric.dumazet@...il.com> Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>, Stephen Hemminger <stephen@...workplumber.org>, Tom Herbert <therbert@...gle.com>, David Miller <davem@...emloft.net>, Hannes Frederic Sowa <hannes@...essinduktion.org>, Daniel Borkmann <dborkman@...hat.com>, Florian Westphal <fw@...len.de>, Toke Høiland-Jørgensen <toke@...e.dk>, Dave Taht <dave.taht@...il.com>, brouer@...hat.com Subject: Re: Qdisc: Measuring Head-of-Line blocking with netperf-wrapper On Tue, 16 Sep 2014 06:59:19 -0700 Eric Dumazet <eric.dumazet@...il.com> wrote: > With the TCP usec rtt work I did lately, you'll get more precise results > from a TCP_RR flow, as Tom and I explained. Here you go, developed a new test: http://people.netfilter.org/hawk/qdisc/experiment01/README.txt http://people.netfilter.org/hawk/qdisc/experiment01/qdisc_prio_hol.conf https://github.com/netoptimizer/netperf-wrapper/commit/7d0241a78e5 The test includes both a TCP_RR and UDP_RR test that derive the latency, also kept the ping tests for comparison. One problem: The NoneXSO test is basically invalid, because I cannot make it exhaust the bandwidth, see "Total Upload": http://people.netfilter.org/hawk/qdisc/experiment01/qdisc_prio_hol__totals--NoneXSO_net_next.png Looking at the ping test, there is a clear difference between priority bands, this just shows that the priority band are working as expected and the qdisc is backlogged. http://people.netfilter.org/hawk/qdisc/experiment01/qdisc_prio_hol__ping--GSO_net_next.png E.g. ping test for NoneXSO show it is not backlogged, a broken test: http://people.netfilter.org/hawk/qdisc/experiment01/qdisc_prio_hol__ping--NoneXSO_net_next.png Zooming in on the high priority band, we see how the different high-prio band measurements are working. Here for GSO: http://people.netfilter.org/hawk/qdisc/experiment01/qdisc_prio_hol__ping_hiprio--GSO_net_next.png Here for TSO: http://people.netfilter.org/hawk/qdisc/experiment01/qdisc_prio_hol__ping_hiprio--TSO_net_next.png I've created a new graph called "rr_latency" that further zooms in on the difference between TCP_RR and UDP_RR measurements: Here for GSO: http://people.netfilter.org/hawk/qdisc/experiment01/qdisc_prio_hol__rr_latency--GSO_net_next.png Here for TSO: http://people.netfilter.org/hawk/qdisc/experiment01/qdisc_prio_hol__rr_latency--TSO_net_next.png A compare graph: http://people.netfilter.org/hawk/qdisc/experiment01/compare_TSO_vs_GSO__rr_latency.png I found the interactions a little strange in the above graphs. Even more strange, I started to play with the ixgbe cleanup interval, adjusting via cmdline: sudo ethtool -C eth4 rx-usecs 30 Then the "rr_latency" graph change, significantly lowering the latetency. Here for GSO: http://people.netfilter.org/hawk/qdisc/experiment01/qdisc_prio_hol__rr_latency--rxusecs30_GSO_net_next.png Here for TSO: http://people.netfilter.org/hawk/qdisc/experiment01/qdisc_prio_hol__totals--rxusecs30_TSO_net_next.png Compare graph for GSO: http://people.netfilter.org/hawk/qdisc/experiment01/compare_GSO_vs_GSO_with_rxusec30__rr_latency.png Compare graph for TSO: http://people.netfilter.org/hawk/qdisc/experiment01/compare_TSO_vs_TSO_with_rxusec30__rr_latency.png Comparing TSO vs GSO both with rx-usecs 30, which is almost equal. http://people.netfilter.org/hawk/qdisc/experiment01/compare_TSO_vs_GSO_both_with_rxusec30__rr_latency.png Checking ping, still follow TCP_RR and UDP_RR, with rx-usecs 30: http://people.netfilter.org/hawk/qdisc/experiment01/qdisc_prio_hol__ping_hiprio--rxusecs30_GSO_net_next.png http://people.netfilter.org/hawk/qdisc/experiment01/qdisc_prio_hol__ping_hiprio--rxusecs30_TSO_net_next.png -- Best regards, Jesper Dangaard Brouer MSc.CS, Sr. Network Kernel Developer at Red Hat Author of http://www.iptv-analyzer.org LinkedIn: http://www.linkedin.com/in/brouer -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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