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Date: Thu, 16 Aug 2007 12:42:00 -0700 From: Rick Jones <rick.jones2@...com> To: Linux Network Development list <netdev@...r.kernel.org> Subject: e1000 autotuning doesn't get along with itself Folks - I was trying to look at bonding vs discrete links and so put a couple dual-port e1000-driven NICs: 4a:01.1 Ethernet controller: Intel Corporation 82546GB Gigabit Ethernet Controller (rev 03) Subsystem: Hewlett-Packard Company HP Dual Port 1000Base-T [A9900A] into a pair of 8 core systems running a 2.6.22.2 kernel. This gave me: hpcpc109:~/netperf2_trunk# ethtool -i eth2 driver: e1000 version: 7.3.20-k2-NAPI firmware-version: N/A bus-info: 0000:49:02.0 for the e1000 driver. I connected the two systems back-to-back and started running some tests. In the course of trying to look at something else (verifying the results reported by bwm-ng) I enabled demo-mode in netperf (./configure --enable-demo) and noticed a considerable oscillation. I undid the bond and repeated the experiment with a discrete NIC: hpcpc109:~/netperf2_trunk# src/netperf -t TCP_RR -H 192.168.2.105 -D 1.0 -l 15 TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.2.105 (192.168.2.105) port 0 AF_INET : demo : first burst 0 Interim result: 10014.93 Trans/s over 1.00 seconds Interim result: 10015.79 Trans/s over 1.00 seconds Interim result: 10014.30 Trans/s over 1.00 seconds Interim result: 10016.29 Trans/s over 1.00 seconds Interim result: 10085.80 Trans/s over 1.00 seconds Interim result: 17526.61 Trans/s over 1.00 seconds Interim result: 20007.60 Trans/s over 1.00 seconds Interim result: 19626.46 Trans/s over 1.02 seconds Interim result: 10616.44 Trans/s over 1.85 seconds Interim result: 10014.88 Trans/s over 1.06 seconds Interim result: 10015.79 Trans/s over 1.00 seconds Interim result: 10014.80 Trans/s over 1.00 seconds Interim result: 10035.30 Trans/s over 1.00 seconds Interim result: 13974.69 Trans/s over 1.00 seconds Local /Remote Socket Size Request Resp. Elapsed Trans. Send Recv Size Size Time Rate bytes Bytes bytes bytes secs. per sec 16384 87380 1 1 15.00 12225.77 16384 87380 On a slightly informed whim I tried disabling the interrupt thottle on both sides (modprobe e1000 InterruptThrottleRate=0,0,0,0,0,0,0,0) and re-ran: hpcpc109:~/netperf2_trunk# src/netperf -t TCP_RR -H 192.168.2.105 -D 1.0 -l 15TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.2.105 (192.168.2.105) port 0 AF_INET : demo : first burst 0 Interim result: 18673.68 Trans/s over 1.00 seconds Interim result: 18685.01 Trans/s over 1.00 seconds Interim result: 18682.30 Trans/s over 1.00 seconds Interim result: 18681.05 Trans/s over 1.00 seconds Interim result: 18680.25 Trans/s over 1.00 seconds Interim result: 18742.44 Trans/s over 1.00 seconds Interim result: 18739.45 Trans/s over 1.00 seconds Interim result: 18723.52 Trans/s over 1.00 seconds Interim result: 18736.53 Trans/s over 1.00 seconds Interim result: 18737.61 Trans/s over 1.00 seconds Interim result: 18744.76 Trans/s over 1.00 seconds Interim result: 18728.54 Trans/s over 1.00 seconds Interim result: 18738.91 Trans/s over 1.00 seconds Interim result: 18735.53 Trans/s over 1.00 seconds Interim result: 18741.03 Trans/s over 1.00 seconds Local /Remote Socket Size Request Resp. Elapsed Trans. Send Recv Size Size Time Rate bytes Bytes bytes bytes secs. per sec 16384 87380 1 1 15.00 18717.94 16384 87380 and then just for grins I tried just disabling it on one side, leaving the other at defaults: hpcpc109:~/netperf2_trunk# src/netperf -t TCP_RR -H 192.168.2.105 -D 1.0 -l 15TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.2.105 (192.168.2.105) port 0 AF_INET : demo : first burst 0 Interim result: 19980.84 Trans/s over 1.00 seconds Interim result: 19997.60 Trans/s over 1.00 seconds Interim result: 19995.60 Trans/s over 1.00 seconds Interim result: 20002.60 Trans/s over 1.00 seconds Interim result: 20011.58 Trans/s over 1.00 seconds Interim result: 19985.66 Trans/s over 1.00 seconds Interim result: 20002.60 Trans/s over 1.00 seconds Interim result: 20010.58 Trans/s over 1.00 seconds Interim result: 20012.60 Trans/s over 1.00 seconds Interim result: 19993.63 Trans/s over 1.00 seconds Interim result: 19979.63 Trans/s over 1.00 seconds Interim result: 19991.58 Trans/s over 1.00 seconds Interim result: 20011.60 Trans/s over 1.00 seconds Interim result: 19948.84 Trans/s over 1.00 seconds Local /Remote Socket Size Request Resp. Elapsed Trans. Send Recv Size Size Time Rate bytes Bytes bytes bytes secs. per sec 16384 87380 1 1 15.00 19990.14 16384 87380 It looks like the e1000 interrupt throttle autotuning works very nicely when the other side isn't doing any, but if the other side is also trying to autotune it doesn't seem to stablize. At least not during a netperf TCP_RR test. Does anyone else see this? To try to eliminate netperf demo mode I re-ran without it and got the same end results. rick jones - 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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