Date: Sun, 2 Oct 2011 09:08:08 -0700 From: Jack Vogel <jfvogel@gmail.com> To: Hooman Fazaeli <fazaeli@sepehrs.com> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Re: em(4) high latency w/o msix Message-ID: <CAFOYbcnUbdrCYyDdSeYOWVNL_vhH_zA1d5B=mgrkoUijHXj-SQ@mail.gmail.com> In-Reply-To: <4E886A3B.7000502@sepehrs.com> References: <4E886A3B.7000502@sepehrs.com>
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On what hardware? Jack On Sun, Oct 2, 2011 at 6:42 AM, Hooman Fazaeli <fazaeli@sepehrs.com> wrote: > > Latest em(4) driver from HEAD seems to have high latency > when MSIX is disabled. > > With MSIX enabled (hw.em.enable_msix=1): > > # ping -c5 192.168.1.83 > PING 192.168.1.83 (192.168.1.83): 56 data bytes > 64 bytes from 192.168.1.83: icmp_seq=0 ttl=64 time=0.055 ms > 64 bytes from 192.168.1.83: icmp_seq=1 ttl=64 time=0.076 ms > 64 bytes from 192.168.1.83: icmp_seq=2 ttl=64 time=0.066 ms > 64 bytes from 192.168.1.83: icmp_seq=3 ttl=64 time=0.051 ms > 64 bytes from 192.168.1.83: icmp_seq=4 ttl=64 time=0.063 ms > > --- 192.168.1.83 ping statistics --- > 5 packets transmitted, 5 packets received, 0.0% packet loss > round-trip min/avg/max/stddev = 0.051/0.062/0.076/0.009 ms > > With MSIX disabled: > > # ping -c5 192.168.1.83 > PING 192.168.1.83 (192.168.1.83): 56 data bytes > 64 bytes from 192.168.1.83: icmp_seq=0 ttl=64 time=0.180 ms > 64 bytes from 192.168.1.83: icmp_seq=1 ttl=64 time=0.164 ms > 64 bytes from 192.168.1.83: icmp_seq=2 ttl=64 time=0.169 ms > 64 bytes from 192.168.1.83: icmp_seq=3 ttl=64 time=0.172 ms > 64 bytes from 192.168.1.83: icmp_seq=4 ttl=64 time=0.167 ms > > --- 192.168.1.83 ping statistics --- > 5 packets transmitted, 5 packets received, 0.0% packet loss > round-trip min/avg/max/stddev = 0.164/0.170/0.180/0.005 ms > > As you see, w/o MSIX, RTT increases by a factor of 3. > > I also tested the following drivers: > - igb(4) from HEAD: OK. > - Stock 7.3-RELEASE: OK. > - Stock 7.4-RELEASE: problem exist. > > Any ideas? > > > > >
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