nouveau module constantly polls i2c, consumes CPU, on unused nvidia / Optimus

[Adrian Wilkins]

First noticed symptom ; lagging keyboard, pausing audio.

Viewing processes in top / system monitor revealed that a kworker process was spiking the CPU every ~10s

perf-top on the affected process output below

Amateur opinion : Looks like nouveau module is constantly polling hardware via I2C bus, most of the time being spent spinning the CPU while waiting for the slow I2C bus to complete data transfers. This causes symptoms in whatever other modules happen to have landed in the same kworker process ; a reboot cleared up the keyboard lag.

This is an Optimus laptop (Intel i915 / nvidia Quadro 3000M) ; the desktop is running on the i915 hardware.

 `sudo rmmod nouveau` # CPU peakiness stops
 `sudo modprobe nouveau` # problem recommences

I shall probably workaround by blacklisting the nouveau module for the time being ; other suggestions in #ubuntu-kernel included sending the sysfs sequences that power off the nvidia hardware in an Optimus combo.

   PerfTop: 258 irqs/sec kernel:100.0% exact: 0.0% [1000Hz cycles], (target_pid: 100)
-----------------------------------------------------------------------------------------------------------------------------------

    97.16% [kernel] [k] ioread32
     1.16% [kernel] [k] delay_tsc
     0.98% [kernel] [k] native_read_tsc
     0.25% [nouveau] [k] nv50_i2c_getscl
     0.21% [kernel] [k] _cond_resched
     0.12% [i2c_algo_bit] [k] sclhi
     0.07% [kernel] [k] acpi_cpufreq_target
     0.04% [kernel] [k] __ticket_spin_lock
     0.01% [kernel] [k] update_wall_time
     0.00% [kernel] [k] perf_rotate_context
     0.00% [kernel] [k] cpufreq_stat_notifier_trans
     0.00% [kernel] [k] __rcu_pending
     0.00% [nouveau] [k] nouveau_bios_embedded_edid
     0.00% [kernel] [k] __schedule
     0.00% [kernel] [k] ns_to_timespec
     0.00% [mei] [k] mei_timer
     0.00% [kernel] [k] tg_load_down
     0.00% [kernel] [k] find_busiest_group
     0.00% [kernel] [k] __x2apic_send_IPI_mask
     0.00% [kernel] [k] logarithmic_accumulation
     0.00% [kernel] [k] process_one_work
     0.00% [kernel] [k] pick_next_task_stop
     0.00% [kernel] [k] idle_balance
     0.00% [kernel] [k] iowrite32

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: linux-image-3.2.0-24-generic 3.2.0-24.37
ProcVersionSignature: Ubuntu 3.2.0-24.37-generic 3.2.14
Uname: Linux 3.2.0-24-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
ApportVersion: 2.0.1-0ubuntu7
Architecture: amd64
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: PCH [HDA Intel PCH], device 0: STAC92xx Analog [STAC92xx Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: adrian 1931 F.... pulseaudio
 /dev/snd/controlC0: adrian 1931 F.... pulseaudio
Card0.Amixer.info:
 Card hw:0 'PCH'/'HDA Intel PCH at 0xf2560000 irq 56'
   Mixer name : 'IDT 92HD90BXX'
   Components : 'HDA:111d76e7,102804a4,00100102'
   Controls : 19
   Simple ctrls : 10
Card1.Amixer.info:
 Card hw:1 'NVidia'/'HDA NVidia at 0xf0080000 irq 17'
   Mixer name : 'Nvidia GPU 12 HDMI/DP'
   Components : 'HDA:10de0012,10de0101,00100100'
   Controls : 25
   Simple ctrls : 5
Date: Mon May 14 14:11:18 2012
HibernationDevice: RESUME=UUID=b7c131ed-ddd8-49ba-822b-c2ea5c5f8354
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
MachineType: Dell Inc. Precision M6600
ProcFB:
 0 nouveaufb
 1 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.2.0-24-generic root=UUID=ed5f31aa-d115-48e5-9013-a1c2783b59b0 ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-3.2.0-24-generic N/A
 linux-backports-modules-3.2.0-24-generic N/A
 linux-firmware 1.79
SourcePackage: linux
StagingDrivers: mei
UpgradeStatus: Upgraded to precise on 2012-04-16 (27 days ago)
dmi.bios.date: 10/18/2011
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A07
dmi.board.name: 04YY4M
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 9
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA07:bd10/18/2011:svnDellInc.:pnPrecisionM6600:pvr01:rvnDellInc.:rn04YY4M:rvrA00:cvnDellInc.:ct9:cvr:
dmi.product.name: Precision M6600
dmi.product.version: 01
dmi.sys.vendor: Dell Inc.

[Joseph Salisbury (jsalisbury)]

Do you know if this issue happened in a previous version of Ubuntu, or is this a new issue?

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v3.4kernel[1] (Not a kernel in the daily directory). Once you've tested the upstream kernel, please remove the 'needs-upstream-testing' tag(Only that one tag, please leave the other tags). This can be done by clicking on the yellow pencil icon next to the tag located at the bottom of the bug description and deleting the 'needs-upstream-testing' text.

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

If you are unable to test the mainline kernel, for example it will not boot, please add the tag: 'kernel-unable-to-test-upstream'.
Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.4-rc7-precise/

[Launchpad Janitor (janitor)]

[Expired for linux (Ubuntu) because there has been no activity for 60 days.]

[Andreas Kern (kerna)]

i see the lag while playing urban terror

echo "N" >/sys/module/drm_kms_helper/parameters/poll

that solves the problem for me (12.04)