* David Miller <[EMAIL PROTECTED]> wrote: > From: Ingo Molnar <[EMAIL PROTECTED]> > Date: Tue, 17 Jun 2008 11:27:06 +0200 > > > when i originally reported it i debugged it back to missing e1000 TX > > completion IRQs. I tried various versions of the driver to figure > > out whether new workarounds for e1000 cover it but it was fruitless. > > There is a 1000 msec internal watchdog timer IRQ within e1000 that > > gets things going if it's stuck. > > Then that explains your latency, the chip is getting stuck and TX > interrupts stop, right.
note that the 1000 msecs timer is AFAIK internal to the e1000 _hardware_, not the driver itself. I.e. probably the firmware detects and works around a hung transmitter. This is not detectable from the OS (it's not an OS timer), but it can be observed by a lot of testing on a totally quiescent system - which i did back then ;-) i also played a lot with the various knobs of the e1000, none of which seemed to help. /me digs in archives i reported it to the e1000 folks in 2006: Date: Mon, 4 Dec 2006 11:24:00 +0100 against 2.6.19. The original report is below - with a trace and various things i tried to debug this. i eventually got the suggestion from Auke to set RxIntDelay=8 which seemed to work around the issue - but since i use a built-in driver i dont have that setting here (RxIntDelay=8 is a module load parameter and not exposed via Kconfig methods) and the e1000 driver does not seem to have changed its default setting for RxIntDelay. 2.6.18-1.2849.fc6 was the last kernel that worked fine. Ingo --------------------> Date: Wed, 13 Dec 2006 22:09:22 +0100 From: Ingo Molnar <[EMAIL PROTECTED]> To: Auke Kok <[EMAIL PROTECTED]> Subject: Re: e1000: 2.6.19 & long packet latencies Cc: Jesse Brandeburg <[EMAIL PROTECTED]>, "Ronciak, John" <[EMAIL PROTECTED]> Jesse, et al., i'm having a weird packet processing latency problem with the e1000 driver and recent kernels. The symptom is this: if i connect to a T60 laptop (which has an on-board e1000) from the outside, i see large delays in network activity, and ssh sessions are very sluggish. ping latencies show it best under a dynticks kernel (but vanilla 2.6.19 is affected too): titan:~/linux/linux> ping e PING europe (10.0.1.15) 56(84) bytes of data. 64 bytes from europe (10.0.1.15): icmp_seq=1 ttl=64 time=0.340 ms 64 bytes from europe (10.0.1.15): icmp_seq=2 ttl=64 time=757 ms 64 bytes from europe (10.0.1.15): icmp_seq=3 ttl=64 time=1001 ms 64 bytes from europe (10.0.1.15): icmp_seq=4 ttl=64 time=1001 ms 64 bytes from europe (10.0.1.15): icmp_seq=5 ttl=64 time=0.356 ms 64 bytes from europe (10.0.1.15): icmp_seq=6 ttl=64 time=2127 ms 64 bytes from europe (10.0.1.15): icmp_seq=7 ttl=64 time=1002 ms 64 bytes from europe (10.0.1.15): icmp_seq=8 ttl=64 time=0.320 ms 64 bytes from europe (10.0.1.15): icmp_seq=9 ttl=64 time=1002 ms 64 bytes from europe (10.0.1.15): icmp_seq=10 ttl=64 time=2004 ms 64 bytes from europe (10.0.1.15): icmp_seq=11 ttl=64 time=1002 ms 64 bytes from europe (10.0.1.15): icmp_seq=12 ttl=64 time=0.303 ms 64 bytes from europe (10.0.1.15): icmp_seq=13 ttl=64 time=1000 ms 64 bytes from europe (10.0.1.15): icmp_seq=14 ttl=64 time=2010 ms 64 bytes from europe (10.0.1.15): icmp_seq=15 ttl=64 time=1009 ms 64 bytes from europe (10.0.1.15): icmp_seq=16 ttl=64 time=0.283 ms i have traced this and the 1000/2000 msecs values come from some sort of e1000-internal 'heartbeat' interrupt. What seems to happen is that RX packet processing is delayed indefinitely and the IRQ just does not arrive. NOTE: the vanilla 2.6.19 kernel shows this too, but the ping delays are 1/HZ. here's a (filtered) trace of such a delay. IRQ 0x219 is the e1000 interrupt: <idle>-0 0D.h1 761236us : do_IRQ (c0272a9b 219 0) IRQ_219-356 0.... 761412us+: e1000_intr (handle_IRQ_event) IRQ_219-356 0.... 761416us : e1000_clean_rx_irq (e1000_intr) IRQ_219-356 0.... 761418us+: e1000_clean_tx_irq (e1000_intr) <idle>-0 0D.h1 2760093us : do_IRQ (c0272a9b 219 0) IRQ_219-356 0.... 2760268us+: e1000_intr (handle_IRQ_event) IRQ_219-356 0.... 2760273us : e1000_clean_rx_irq (e1000_intr) IRQ_219-356 0.... 2760275us : e1000_clean_tx_irq (e1000_intr) <idle>-0 0D.h1 3804499us : do_IRQ (c0272a9b 219 0) IRQ_219-356 0.... 3804674us+: e1000_intr (handle_IRQ_event) IRQ_219-356 0.... 3804679us+: e1000_clean_rx_irq (e1000_intr) IRQ_219-356 0.... 3804761us : e1000_clean_tx_irq (e1000_intr) IRQ_219-356 0.... 3804763us : e1000_clean_rx_irq (e1000_intr) IRQ_219-356 0.... 3804765us : e1000_clean_tx_irq (e1000_intr) softirq--7 0.... 3804810us : net_rx_action (ksoftirqd) softirq--5 0D.h. 3805425us : do_IRQ (c01598ac 219 0) IRQ_219-356 0.... 3805499us+: e1000_intr (handle_IRQ_event) IRQ_219-356 0.... 3805504us : e1000_clean_rx_irq (e1000_intr) IRQ_219-356 0.... 3805506us : e1000_clean_tx_irq (e1000_intr) IRQ_219-356 0.... 3805547us : e1000_clean_rx_irq (e1000_intr) IRQ_219-356 0.... 3805549us : e1000_clean_tx_irq (e1000_intr) softirq--6 0.... 3805641us : net_tx_action (ksoftirqd) <idle>-0 0D.h1 4760910us : do_IRQ (c01451d4 219 0) IRQ_219-356 0.... 4761347us+: e1000_intr (handle_IRQ_event) IRQ_219-356 0.... 4761352us : e1000_clean_rx_irq (e1000_intr) IRQ_219-356 0.... 4761353us : e1000_clean_tx_irq (e1000_intr) <idle>-0 0D.h1 6761309us : do_IRQ (c0272a9b 219 0) IRQ_219-356 0.... 6761483us+: e1000_intr (handle_IRQ_event) IRQ_219-356 0.... 6761488us : e1000_clean_rx_irq (e1000_intr) IRQ_219-356 0.... 6761490us : e1000_clean_tx_irq (e1000_intr) softirq--5 0D.h. 8760595us : do_IRQ (c0135dc4 219 0) IRQ_219-356 0.... 8760676us+: e1000_intr (handle_IRQ_event) IRQ_219-356 0.... 8760681us+: e1000_clean_rx_irq (e1000_intr) IRQ_219-356 0.... 8760739us : e1000_clean_tx_irq (e1000_intr) IRQ_219-356 0.... 8760740us : e1000_clean_rx_irq (e1000_intr) IRQ_219-356 0.... 8760742us : e1000_clean_tx_irq (e1000_intr) softirq--7 0.... 8760885us : net_rx_action (ksoftirqd) softirq--7 0.... 8760914us+: icmp_rcv (ip_local_deliver) softirq--7 0.... 8760923us+: icmp_reply (icmp_echo) <idle>-0 0D.h1 8761661us : do_IRQ (c0272a9b 219 0) IRQ_219-356 0.... 8761833us+: e1000_intr (handle_IRQ_event) IRQ_219-356 0.... 8761838us : e1000_clean_rx_irq (e1000_intr) IRQ_219-356 0.... 8761840us : e1000_clean_tx_irq (e1000_intr) IRQ_219-356 0.... 8761875us : e1000_clean_rx_irq (e1000_intr) IRQ_219-356 0.... 8761876us : e1000_clean_tx_irq (e1000_intr) softirq--6 0.... 8761921us : net_tx_action (ksoftirqd) note that timestamps 2760093us, 4760910us, 6761309us and 8760595us is some sort of traffic-independent 'periodic' interrupt that e1000 generates. That 'housekeeping' interrupt doesnt seem to be doing much. The IRQ at 8760595us picks up an icmp packet and replies to it - but the icmp packet in reality arrived somewhere between timestamps 6761309us and 8760595us - but no IRQ was generated for it! Suspecting the interrupt-rate controlling bits of the e1000 hw i have tried the following tunes too: -#define DEFAULT_RDTR 0 +#define DEFAULT_RDTR 1 -#define DEFAULT_RADV 128 +#define DEFAULT_RADV 1 -#define DEFAULT_TIDV 64 +#define DEFAULT_TIDV 1 -#define DEFAULT_TADV 64 +#define DEFAULT_TADV 1 -#define DEFAULT_ITR 8000 +#define DEFAULT_ITR 100000 but they made no difference. a 2.6.18-ish kernel works fine (2.6.18-1.2849.fc6): titan:~/linux/linux> ping e PING europe (10.0.1.15) 56(84) bytes of data. 64 bytes from europe (10.0.1.15): icmp_seq=1 ttl=64 time=0.695 ms 64 bytes from europe (10.0.1.15): icmp_seq=2 ttl=64 time=0.171 ms 64 bytes from europe (10.0.1.15): icmp_seq=3 ttl=64 time=0.184 ms 64 bytes from europe (10.0.1.15): icmp_seq=4 ttl=64 time=0.159 ms 64 bytes from europe (10.0.1.15): icmp_seq=5 ttl=64 time=0.148 ms e1000: 0000:02:00.0: e1000_probe: (PCI Express:2.5Gb/s:Width x1) 00:16:41:17:49:d2 e1000: eth0: e1000_probe: Intel(R) PRO/1000 Network Connection the precise hardware version is: 02:00.0 Ethernet controller: Intel Corporation 82573L Gigabit Ethernet Controller Subsystem: Lenovo ThinkPad T60 Flags: bus master, fast devsel, latency 0, IRQ 90 Memory at ee000000 (32-bit, non-prefetchable) [size=128K] I/O ports at 2000 [size=32] Capabilities: <access denied> this laptop has a CoreDuo so i have tried maxcpus=1 too, but it didnt make any difference. Any ideas about what i should try next? Ingo ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php _______________________________________________ E1000-devel mailing list E1000-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/e1000-devel