Re: [TCP]: TCP_DEFER_ACCEPT causes leak sockets

From: Ingo Molnar
Date: Tue Jun 17 2008 - 05:40:27 EST

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* David Miller <davem@xxxxxxxxxxxxx> wrote:

> From: Ingo Molnar <mingo@xxxxxxx>
> 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 <mingo@xxxxxxx>
To: Auke Kok <auke-jan.h.kok@xxxxxxxxx>
Subject: Re: e1000: 2.6.19 & long packet latencies
Cc: Jesse Brandeburg <jesse.brandeburg@xxxxxxxxx>,
"Ronciak, John" <john.ronciak@xxxxxxxxx>

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
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Next message: Bartlomiej Zolnierkiewicz: "Re: [PATCH] cdrom: don't check CDC_PLAY_AUDIO in cdrom_count_tracks()"
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In reply to: David Miller: "Re: [TCP]: TCP_DEFER_ACCEPT causes leak sockets"
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