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Date: Tue, 16 Dec 2008 22:55:47 +0000 From: "Tvrtko A. Ursulin" <tvrtko@...ulin.net> To: Chris Snook <csnook@...hat.com> Cc: netdev@...r.kernel.org Subject: Re: Bonding gigabit and fast? On Tuesday 16 December 2008 20:37:47 Chris Snook wrote: > >> The gigabit card might be sharing a PCI bus with your disk controller, > >> so swapping which slots the cards are in might make gigabit work faster, > >> but it sounds more like the driver is doing something stupid with > >> interrupt servicing. > > > > Dang you are right, they really do share the same interrupt. And I have > > nowhere else to move that card since it is a single PCI slot. > > Interestingly, fast ethernet (eth0) generates double number of interrupts > > than gigabit (eth1) and SATA combined. > > > > From powertop: > > > > Top causes for wakeups: > > 65.5% (11091.1) <interrupt> : eth0 > > 32.9% (5570.5) <interrupt> : sata_sil, eth1 > > > > Tvrtko > > Sharing an interrupt shouldn't be a problem, unless the other driver is > doing bad things. Sharing the bus limits PCI bandwidth though, and that > can hurt. > > The fact that you're getting more interrupts on the card moving more > packets isn't surprising. > > It occurred to me that the alb algorithm is not designed for asymmetric > bonds, so part of the problem is likely the distribution of traffic. You > always end up with somewhat unbalanced distribution, and it happens to be > favoring the slower card. I was using balance-rr, alb flavour does not seem to like 8139too. > The real problem is that you get such lousy performance in unbonded gigabit > mode. Try oprofiling it to see where it's spending all that time. Could it be something scheduling related? Or maybe CIFS on the client which is also running a flavour of 2.6.27? I had to put vanilla 2.6.27.9 on the server in order to run oprofile so maybe I'll have to do the same thing on the client.. In the meantime these are the latest testing results. When serving over Samba I get 9.6Mb/s and oprofile looks like this: Counted CPU_CLK_UNHALTED events (Cycles outside of halt state) with a unit mask of 0x00 (No unit mask) count 100000 samples % image name app name symbol name 43810 11.2563 skge skge (no symbols) 36363 9.3429 vmlinux vmlinux handle_fasteoi_irq 32805 8.4287 vmlinux vmlinux __napi_schedule 30122 7.7394 vmlinux vmlinux handle_IRQ_event 22270 5.7219 vmlinux vmlinux copy_user_generic_string 13444 3.4542 vmlinux vmlinux native_read_tsc 7606 1.9542 smbd smbd (no symbols) 7492 1.9250 vmlinux vmlinux mcount 6014 1.5452 libmythui-0.21.so.0.21.0 libmythui-0.21.so.0.21.0 (no symbols) 5689 1.4617 vmlinux vmlinux memcpy_c 5090 1.3078 libc-2.8.90.so libc-2.8.90.so (no symbols) 4176 1.0730 vmlinux vmlinux native_safe_halt 3970 1.0200 vmlinux vmlinux ioread8 It is generally not very CPU intensive, but as I said it oscillates a lot. For example vmstat 1 output from middle of this transfer: 1 0 0 33684 18908 532240 0 0 8832 128 8448 1605 0 9 86 5 0 0 0 21040 18908 544768 0 0 12544 0 11615 1876 0 10 89 1 0 0 0 17168 18908 548636 0 0 3840 0 3999 978 0 5 95 0 0 0 0 10904 18972 554412 0 0 5772 0 5651 1050 1 7 86 6 1 0 0 8976 18840 556312 0 0 3200 0 3573 891 0 4 96 0 0 0 0 9948 18792 555716 0 0 7168 0 6776 1202 0 9 89 2 Or bandwith log (500msec period): 1229466433;eth1;6448786.50;206129.75;6654916.50;103271;3230842;4483.03;2608.78;7091.82;1307;2246;0.00;0.00;0;0 1229466433;eth1;11794112.00;377258.00;12171370.00;188629;5897056;8186.00;4772.00;12958.00;2386;4093;0.00;0.00;0;0 1229466434;eth1;4417197.50;141690.62;4558888.50;70987;2213016;3069.86;1792.42;4862.28;898;1538;0.00;0.00;0;0 1229466434;eth1;6059886.00;194222.00;6254108.00;97111;3029943;4212.00;2458.00;6670.00;1229;2106;0.00;0.00;0;0 1229466435;eth1;9232362.00;295816.38;9528178.00;148204;4625413;6413.17;3742.52;10155.69;1875;3213;0.00;0.00;0;0 1229466435;eth1;20735192.00;663600.00;21398792.00;331800;10367596;14398.00;8400.00;22798.00;4200;7199;0.00;0.00;0;0 1229466436;eth1;12515441.00;399852.31;12915294.00;200326;6270236;8688.62;5063.87;13752.50;2537;4353;0.00;0.00;0;0 On the other hand when I pulled the same file with scp I got pretty stable 22.3 Mb/s and this oprofile: samples % image name app name symbol name 242779 48.4619 libcrypto.so.0.9.8 libcrypto.so.0.9.8 (no symbols) 30214 6.0311 skge skge (no symbols) 29276 5.8439 vmlinux vmlinux copy_user_generic_string 21052 4.2023 vmlinux vmlinux handle_fasteoi_irq 19124 3.8174 vmlinux vmlinux __napi_schedule 15394 3.0728 libc-2.8.90.so libc-2.8.90.so (no symbols) 14327 2.8599 vmlinux vmlinux handle_IRQ_event 5303 1.0585 vmlinux vmlinux native_read_tsc Hm, let me do one more test which has no CPU taxing network transport like netcat. Nope, same "fast" ~22Mb/s speed, or: samples % image name app name symbol name 29719 11.5280 vmlinux vmlinux copy_user_generic_string 28354 10.9985 skge skge (no symbols) 18259 7.0826 vmlinux vmlinux handle_fasteoi_irq 17359 6.7335 vmlinux vmlinux __napi_schedule 15095 5.8553 vmlinux vmlinux handle_IRQ_event 7422 2.8790 vmlinux vmlinux native_read_tsc 5619 2.1796 vmlinux vmlinux mcount 3966 1.5384 libmythui-0.21.so.0.21.0 libmythui-0.21.so.0.21.0 (no symbols) 3709 1.4387 libc-2.8.90.so libc-2.8.90.so (no symbols) 3510 1.3615 vmlinux vmlinux memcpy_c Maybe also NFS.. no, also fast. So this points to Samba/scheduler/CIFS client regression I think. I'll try to do more testing in the following days. All this assuming that ~22Mb/s is the best this machine can do and only hunting for slow and unstable speed over Samba. But I find it strange iperf also couldn't do more and it does not put any load on the shared interrupt line. Especially since it did 400Mbps in the other direction. Thank you for your help of course, forgot to say it earlier! Tvrtko -- 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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