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Date: Fri, 23 Aug 2013 14:46:20 +0200
From: Martin Mokrejs <mmokrejs@...d.natur.cuni.cz>
To: Peter Zijlstra <peterz@...radead.org>
CC: Theodore Tso <tytso@....edu>, Thomas Gleixner <tglx@...utronix.de>,
mingo@...hat.com, LKML <linux-kernel@...r.kernel.org>,
Johannes Berg <johannes@...solutions.net>
Subject: Re: [sched_delayed] sched: RT throttling activated
Peter Zijlstra wrote:
> On Fri, Aug 23, 2013 at 01:35:24PM +0200, Martin Mokrejs wrote:
>
>> # ps -deo pid,cls,cmd | grep -e 'RR \[' -e 'FF \['
>
> This explicitly only lists kernel threads; from your other comment:
>
>> The shell/python tasks have 'TS' in place of the FF value in the second column
>> so I guess they are not requiring realtime responsiveness.
>
> I'll assume you actually inspected the other tasks and found none.
Yes, the other (false) matches were in the third or latter columns so I wanted to match
just those true matches and cut&paste it. I admit, this is not a general-purpose
REGEXP and is misleading.
>
>> 7 FF [migration/0]
>> 10 FF [watchdog/0]
>> 11 FF [watchdog/1]
>> 12 FF [migration/1]
>> 17 FF [migration/2]
>> 22 FF [migration/3]
>
> The 'migration' threads only look like FIFO threads but they're secretly
> not and don't count to the limit. The watchdog threads shouldn't run
> much either.
>
>> 2161 FF [irq/50-iwlwifi]
>
> Oh a threaded interrupt, I presume you're not using "threadiqrs" since
Is that what you talk about?
CONFIG_IRQ_FORCED_THREADING=y
CONFIG_GENERIC_SMP_IDLE_THREAD=y
> this is the only interrupt thread around and I see a
> 'request_threaded_irq()' call in
> drivers/net/wireless/iwlwifi/pcie/trans.c
>
> And wow, why would that thing consume that much cpu.
>
> Johill, ever seen the iwlwifi interrupt go 'funny' and consume gobs of
> cpu-time?
I am not sure if I understand you but in case it helps somebody
Current values:
# cat /proc/interrupts
CPU0 CPU1
0: 23 0 IO-APIC-edge timer
1: 42 0 IO-APIC-edge i8042
8: 36 0 IO-APIC-edge rtc0
9: 3 0 IO-APIC-fasteoi acpi
12: 404650 0 IO-APIC-edge i8042
16: 109 0 IO-APIC-fasteoi ehci_hcd:usb1
23: 583646 0 IO-APIC-fasteoi ehci_hcd:usb2
40: 0 0 PCI-MSI-edge pciehp
41: 54319 0 PCI-MSI-edge i915
42: 553802 0 PCI-MSI-edge ahci
43: 0 0 PCI-MSI-edge enp5s0
44: 257268 0 PCI-MSI-edge xhci_hcd
45: 0 0 PCI-MSI-edge xhci_hcd
46: 0 0 PCI-MSI-edge xhci_hcd
47: 0 0 PCI-MSI-edge xhci_hcd
48: 0 0 PCI-MSI-edge xhci_hcd
49: 465462 0 PCI-MSI-edge snd_hda_intel
50: 3895788 0 PCI-MSI-edge iwlwifi
NMI: 8687 9483 Non-maskable interrupts
LOC: 17531664 16978131 Local timer interrupts
SPU: 0 0 Spurious interrupts
PMI: 8687 9483 Performance monitoring interrupts
IWI: 213009 205171 IRQ work interrupts
RTR: 3 0 APIC ICR read retries
RES: 1922651 4491695 Rescheduling interrupts
CAL: 73741 348678 Function call interrupts
TLB: 98634 111173 TLB shootdowns
TRM: 0 0 Thermal event interrupts
THR: 0 0 Threshold APIC interrupts
MCE: 0 0 Machine check exceptions
MCP: 286 286 Machine check polls
ERR: 0
MIS: 0
# ifconfig wlp9s0
wlp9s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.0.24 netmask 255.255.255.0 broadcast 192.168.0.255
inet6 fe80::4e80:93ff:fe15:e6c7 prefixlen 64 scopeid 0x20<link>
ether 4c:80:93:15:e6:c7 txqueuelen 1000 (Ethernet)
RX packets 811806 bytes 992611146 (946.6 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 490006 bytes 71390887 (68.0 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
# dmesg
...
[ 11.789302] Intel(R) Wireless WiFi driver for Linux, in-tree:d
[ 11.789310] Copyright(c) 2003-2013 Intel Corporation
[ 11.791626] iwlwifi 0000:09:00.0: irq 50 for MSI/MSI-X
[ 12.044905] iwlwifi 0000:09:00.0: loaded firmware version 18.168.6.1 op_mode iwldvm
[ 13.896033] iwlwifi 0000:09:00.0: CONFIG_IWLWIFI_DEBUG enabled
[ 13.896041] iwlwifi 0000:09:00.0: CONFIG_IWLWIFI_DEBUGFS disabled
[ 13.896044] iwlwifi 0000:09:00.0: CONFIG_IWLWIFI_DEVICE_TRACING disabled
[ 13.896047] iwlwifi 0000:09:00.0: CONFIG_IWLWIFI_DEVICE_TESTMODE disabled
[ 13.896049] iwlwifi 0000:09:00.0: CONFIG_IWLWIFI_P2P disabled
[ 13.896054] iwlwifi 0000:09:00.0: Detected Intel(R) Centrino(R) Wireless-N 1030 BGN, REV=0xB0
[ 13.896173] iwlwifi 0000:09:00.0: L1 Disabled; Enabling L0S
[ 13.917705] ieee80211 phy0: Selected rate control algorithm 'iwl-agn-rs'
>
>
>>> Nope, you get that message once to tell you that we throttle RT tasks.
>>
>> I think the message could improved to explain this is a warn ONCE message and
>> that there is no "[sched_delayed] sched: RT throttling deactivated" counterpart
>> message to be anticipated.
>
> Would something like:
>
> sched: [ONCE] RT throttle hit -- inspect system configuration.
>
> Be a better message?
Not really. I would prefer something like:
[sched_delayed] sched: stopped running $cmd on CPU%d in favor of RR/FIFO task $psname
where the "$cmd" would be something like what "ps -deo pid,cls,cmd | grep -e RR -e FF" gives?
Still, I think when the interrupted task is ran again, a "counterpart" message should be logged.
Especially to see the timing between them could be helpful?
>
> Also, could you clarify what exact kernel version you're running? I
> couldn't find it in your previous messages.
Vanilla 3.10.9, I thought it was in the very first message ...
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