Date: Thu, 23 Dec 2004 17:12:38 -0700 From: Scott Long <scottl@freebsd.org> To: Christian Weisgerber <naddy@mips.inka.de> Cc: Robert Watson <rwatson@freebsd.org> Subject: Re: 5.3-STABLE/alpha: re(4) slowdown Message-ID: <41CB5EF6.8030704@freebsd.org> In-Reply-To: <20041223200429.GA3869@kemoauc.mips.inka.de> References: <cqdegv$1na$1@kemoauc.mips.inka.de> <Pine.NEB.3.96L.1041223102643.89131D-100000@fledge.watson.org> <20041223200429.GA3869@kemoauc.mips.inka.de>
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Christian Weisgerber wrote: > Robert Watson: > > >>Could you use a tool like netperf to see whether the slowdown is specific >>to TCP, or affects UDP also? There have been some TCP tweaks and >>bugfixes, and this would help isolate that. Seeing the results of a >>netperf run with the UDP_RR and UDP_STREAM tests in the "before" and >>"after" scenarios would be helpful. > > > 5.3-STABLE (RELENG_5) on alpha; GENERIC plus if_re.ko. > The transmitting side is OpenBSD-current/amd64 (GENERIC, sk). > The network is a no-name dumb gigabit switch. No jumbo frames. > > Results from five runs in a row. > > Kernel as of December 4: > > netperf -H 172.16.0.3 -t TCP_STREAM > TCP STREAM TEST to 172.16.0.3 > Recv Send Send > Socket Socket Message Elapsed > Size Size Size Time Throughput > bytes bytes bytes secs. 10^6bits/sec > > 65536 16384 16384 10.00 142.11 > 65536 16384 16384 10.01 142.58 > 65536 16384 16384 10.01 137.59 > 65536 16384 16384 10.01 135.01 > 65536 16384 16384 10.01 139.23 > > December 22: > > netperf -H 172.16.0.3 -t TCP_STREAM > TCP STREAM TEST to 172.16.0.3 > Recv Send Send > Socket Socket Message Elapsed > Size Size Size Time Throughput > bytes bytes bytes secs. 10^6bits/sec > > 65536 16384 16384 10.08 2.57 > 65536 16384 16384 10.66 4.50 > 65536 16384 16384 10.06 6.16 > 65536 16384 16384 12.10 6.73 > 65536 16384 16384 10.10 2.84 > > Both the switch lights and the feeling from, say, scrolling in a > Firefox window from a remote host suggest that there are short > periods where no packets are transmitted. > > > December 4: > > netperf -H 172.16.0.3 -t UDP_STREAM > UDP UNIDIRECTIONAL SEND TEST to 172.16.0.3 > Socket Message Elapsed Messages > Size Size Time Okay Errors Throughput > bytes bytes secs # # 10^6bits/sec > > 9216 9216 10.00 22783 219677 167.94 > 42080 10.00 4 0.03 > > (The large socket size tests all fail, which I presume is irrelevant in > this context. Figures from further runs:) > > 9216 9216 10.00 22285 225815 164.22 > 9216 9216 10.00 23852 224714 175.78 > 9216 9216 10.01 23635 225654 174.13 > 9216 9216 10.01 24139 224133 177.86 > > December 22: > > netperf -H 172.16.0.3 -t UDP_STREAM > UDP UNIDIRECTIONAL SEND TEST to 172.16.0.3 > Socket Message Elapsed Messages > Size Size Time Okay Errors Throughput > bytes bytes secs # # 10^6bits/sec > > 9216 9216 10.01 24410 221169 179.84 > 42080 10.01 20 0.15 > > I would have said that UDP is not affected, except that at this > point the FreeBSD box locked up solid. > I suspect that the buffers are being bounced all over the place in the if_re driver. Can you send me the output of 'sysctl hw.busdma' after the system has been under load? Scott
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