Direct Rendering Infrastructure

https://bugzilla.kernel.org/show_bug.cgi?id=16265





--- Comment #1 from Rafael J. Wysocki <rjw@...>  2010-07-23 20:03:18 ---
On Friday, July 23, 2010, Nick Bowler wrote:
> On 13:47 Fri 23 Jul     , Rafael J. Wysocki wrote:
> > This message has been generated automatically as a part of a summary report
> > of recent regressions.
> > 
> > The following bug entry is on the current list of known regressions
> > from 2.6.34.  Please verify if it still should be listed and let the tracking team
> > know (either way).
> > 
> > 
> > Bug-Entry	: http://bugzilla.kernel.org/show_bug.cgi?id=16265
> > Subject		: Why is kslowd accumulating so much CPU time?
> > Submitter	: Theodore Ts'o <tytso@...>
> > Date		: 2010-06-09 18:36 (45 days old)
> 
> I actually haven't been able to reproduce with kernels since a couple
> weeks ago (still reproducible if I go back to 2.6.35-rc3, though).
> Seems to be fixed somehow, can anyone else confirm?

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Rafael J. Wysocki <rjw@...> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |UNREPRODUCIBLE




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Thomas Lindroth <thomas.lindroth@...> changed:

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                 CC|                            |thomas.lindroth@...




--- Comment #2 from Thomas Lindroth <thomas.lindroth@...>  2010-07-24 13:19:51 ---
I'm still experiencing what I believe to be this bug on 2.6.35-rc6. The mouse
stalls every few seconds and the kslowd threads use a lot of cpu when the mouse
stalls. The problem started after upgrading from 2.6.34.

I'm using an intel 965GM connected with HDMI.

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Rafael J. Wysocki <rjw@...> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|UNREPRODUCIBLE              |




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Rafael J. Wysocki <rjw@...> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |NEW




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alfonso.pola@... changed:

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                 CC|                            |alfonso.pola@...

Chris Wilson <chris@...> changed:

           What    |Removed                     |Added
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                 CC|                            |chris@...




--- Comment #3 from alfonso.pola@...  2010-08-12 00:15:51 ---
I'm having this problem with kernel 2.6.35.1 in archlinux. I'm willing to
provide debugging information, I just don't know what should I post. I have a
lenovo sl300 laptop with intel integrated graphics (HD4500 I believe).

--- Comment #4 from Chris Wilson <chris@...>  2010-08-13 08:13:45 ---
Ok, we understand what's going on here now. Every 10s the non-hotplug capable
outputs are polled for connection/disconnection events. For a certain class of
analog device on some hardware this is very slow and CPU intensive.

See also https://bugs.freedesktop.org/show_bug?id=29536

The first workaround proposed is just to disable polling via a module
parameter. The eventual solution will likely be a mix of finer grained locking
and cheaper, non-destructive polling.

--- Comment #5 from alfonso.pola@...  2010-08-13 19:51:15 ---
ok, cool.

PS: The link is http://bugs.freedesktop.org/show_bug.cgi?id=29536

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Florian Mickler <florian@...> changed:

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                 CC|                            |florian@...




--- Comment #6 from Florian Mickler <florian@...>  2010-09-07 06:37:49 ---
Handled-By: Chris Wilson <chris@...>
References: http://bugs.freedesktop.org/show_bug.cgi?id=29536

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Takehiko Abe <keke@...> changed:

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                 CC|                            |keke@...




--- Comment #7 from Takehiko Abe <keke@...>  2010-09-22 11:58:39 ---
The "automatic workaround" does not work for me. I needed to set the
module parameter to "disable polling". There is a similar bug
reported:

Bug 18802 kworker: high CPU usage -> system sluggish
https://bugzilla.kernel.org/show_bug.cgi?id=18802

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Florian Mickler <florian@...> changed:

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                 CC|                            |edwintorok@...




--- Comment #8 from Florian Mickler <florian@...>  2011-01-12 10:48:30 ---
*** Bug 18802 has been marked as a duplicate of this bug. ***

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--- Comment #9 from Florian Mickler <florian@...>  2011-01-12 11:19:26 ---
Is this issue still visible on 2.6.37?

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Florian Mickler <florian@...> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |CODE_FIX




--- Comment #10 from Florian Mickler <florian@...>  2011-01-12 11:37:46 ---
I'm closing this for now, please reopen or shout if this issue is still
unresolved for you. 

This should have been fixed for intel since 2.6.36-rc5: 

commit 930a9e283516a3a3595c0c515113f1b78d07f695
Author: Chris Wilson <chris@...>
Date:   Tue Sep 14 11:07:23 2010 +0100

    drm: Use a nondestructive mode for output detect when polling (v2)


for nouveau it's probably fixed since v2.6.37-rc3:

commit 01db363979e96115a895f35c823303660f0f328d
Author: Francisco Jerez <currojerez@...>
Date:   Thu Oct 21 17:43:08 2010 +0200

    drm/nouveau: Use "force" to decide if analog load detection is ok or not.



and for radeon since v2.6.37-rc1:

commit c3cceeddf0b5f97b0d2352b98ef0f025e31a9ae3
Author: Dave Airlie <airlied@...>
Date:   Tue Oct 26 12:55:52 2010 +1000

    drm/radeon/kms: don't poll dac load detect.

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Florian Mickler <florian@...> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |CLOSED




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Bc. Slavomir Danas <slavomir.danas@...> changed:

           What    |Removed                     |Added
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                 CC|                            |slavomir.danas@...




--- Comment #11 from Bc. Slavomir Danas <slavomir.danas@...>  2011-01-15 20:42:49 ---
This issue is still present for me with Intel 4500 MHD (intel driver 2.14.0,
xorg-server 1.9.3.901, mesa 7.9.1, libdrm 2.4.23) with gentoo-sources 2.6.37.
I've read this announcement and disabled my drm_kms_helper.poll=N kernel boot
param but the issue has come up after few minutes after booting. System was
sluggish and kworker process appeared eating 60% CPU.

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--- Comment #12 from Chris Wilson <chris@...>  2011-01-15 22:35:48 ---
(In reply to comment #11)
> This issue is still present for me with Intel 4500 MHD (intel driver 2.14.0,
> xorg-server 1.9.3.901, mesa 7.9.1, libdrm 2.4.23) with gentoo-sources 2.6.37.
> I've read this announcement and disabled my drm_kms_helper.poll=N kernel boot
> param but the issue has come up after few minutes after booting. System was
> sluggish and kworker process appeared eating 60% CPU.

Different culprit - you neither have the affected hardware nor the responsible
hotplug polling enabled.

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--- Comment #13 from Bc. Slavomir Danas <slavomir.danas@...>  2011-01-16 09:04:37 ---
I have been redirected here from
https://bugzilla.kernel.org/show_bug.cgi?id=18802 so it is probably not a
duplicate of this bug because the workaround there did work for me.

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--- Comment #14 from Florian Mickler <florian@...>  2011-01-16 12:46:57 ---
You write in comment #11 about 'disabling the boot drm_kms_helper.poll=N'... 

Did you mean with that, that the problem is in 2.6.37 (final) still present and
only solved by putting drm_kms_helper.poll=N on the commandline... 


or 

Even with polling disabled via the commandline drm_kms_helper.poll=N you
experience the symptoms?


Regards,
Flo

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--- Comment #15 from Bc. Slavomir Danas <slavomir.danas@...>  2011-01-16 19:45:49 ---
I've had this drm_kms_helper.poll=N kernel workaround in my grub since I've
discovered it in 18802 bug (around 2.6.36-r2 i think) because I've suffered by
the udev drm polling storm in 2.6.34, kslowd in 2.6.35 and kworker in 2.6.36.
Since I've applied it everything was working smooth. I read the announcement
about bug 18802 being duplicate of this bug and it being resolved as of
2.6.36-rc5 so I have removed this kernel setting and rebooted with my 2.6.37
kernel hoping that everything should be fine. But in few minutes the same
symptoms appeared so I reverted back to drm_kms_helper.poll=N kernel option and
everything seems all right again (with the workaround). I can provide more info
on my HW or SW by request.

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--- Comment #16 from Chris Wilson <chris@...>  2011-01-16 22:46:41 ---
You need to quantify your observations here. When polling is enabled, then
every 10s the worker will be awoken and consume CPU time checking that all the
displays are the same as before. Unless on your machine it takes a ridiculous
amount of CPU time (say greater than 5%), it is just the cost of the ability
for your computer to automatically detect display changes.

The real bug is the latency it induces... But I digress.

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--- Comment #17 from Bc. Slavomir Danas <slavomir.danas@...>  2011-01-18 18:18:36 ---
It doesn't seem to me as sane to consume this amount of CPU time to poll for
anything (see attached screenshot). I figured a way how to reproduce this, I've
enabled RandR polling in KDE, attached LCD TV via HDMI and played a video in
VLC. After few mouse clicks in the menu of VLC I've witnessed jerky mouse
movement and later my X has frozen completely. I've switched to console and
found out that when I unpluged HDMI the kworker process went quiet.
I was able to take one screenshot but as my X froze I saw 3 kworker processes
running, eating all CPU time rendering my system useless (no chance to take
screenshot at that moment).
I repeat I'm running latest gentoo-sources-2.6.37.

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--- Comment #18 from Bc. Slavomir Danas <slavomir.danas@...>  2011-01-18 18:19:30 ---
Created an attachment (id=44072)
 --> (https://bugzilla.kernel.org/attachment.cgi?id=44072)
kslowd in 2.6.37

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--- Comment #19 from Bc. Slavomir Danas <slavomir.danas@...>  2011-04-09 16:48:51 ---
You should definetely reopen this as I still have issues on 2.6.38. Will
provide anything to help you resolve it. See following attachement...

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--- Comment #20 from Bc. Slavomir Danas <slavomir.danas@...>  2011-04-09 16:51:37 ---
Created an attachment (id=53912)
 --> (https://bugzilla.kernel.org/attachment.cgi?id=53912)
kworker polling hogs CPU on 2.6.38

kworker polling hogs CPU on 2.6.38
Gentoo x64
gentoo-sources 2.6.38
HP ProBook 4510s

00:02.0 VGA compatible controller [0300]: Intel Corporation Mobile 4 Series
Chipset Integrated Graphics Controller [8086:2a42] (rev 07) (prog-if 00 [VGA
controller])
        Subsystem: Hewlett-Packard Company Device [103c:3072]
        Flags: bus master, fast devsel, latency 0, IRQ 44
        Memory at d0000000 (64-bit, non-prefetchable) [size=4M]
        Memory at c0000000 (64-bit, prefetchable) [size=256M]
        I/O ports at 50f0 [size=8]
        Expansion ROM at <unassigned> [disabled]
        Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
        Capabilities: [d0] Power Management version 3
        Kernel driver in use: i915

Attached external LCD TV at 720p via HDMI cable

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--- Comment #21 from Chris Wilson <chris@...>  2011-04-09 17:01:53 ---
Please do a "perf top" to see what tasklet is actually being run by kslowd.

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--- Comment #22 from Bc. Slavomir Danas <slavomir.danas@...>  2011-04-09 17:45:57 ---
This is while kslowd consumed approx. 75% CPU:


   PerfTop:       0 irqs/sec  kernel:-nan%  exact: -nan% [1000Hz cycles], 
(all, 2 CPUs)

             3215.00 86.8% delay_tsc                    
/lib/modules/2.6.38-ck-BKL/build/vmlinux
              163.00  4.4% read_hpet                    
/lib/modules/2.6.38-ck-BKL/build/vmlinux
              110.00  3.0% set_clock                    
/lib/modules/2.6.38-ck-BKL/build/vmlinux
               55.00  1.5% get_clock                    
/lib/modules/2.6.38-ck-BKL/build/vmlinux
               45.00  1.2% get_data                     
/lib/modules/2.6.38-ck-BKL/build/vmlinux
               28.00  0.8% rb_next                      
/lib/modules/2.6.38-ck-BKL/build/vmlinux
                7.00  0.2% _raw_spin_lock_irqsave       
/lib/modules/2.6.38-ck-BKL/build/vmlinux
                7.00  0.2% hpet_legacy_next_event       
/lib/modules/2.6.38-ck-BKL/build/vmlinux
                7.00  0.2% set_data                     
/lib/modules/2.6.38-ck-BKL/build/vmlinux
                6.00  0.2% __pthread_mutex_lock_internal
/lib64/libpthread-2.11.3.so             
                5.00  0.1% acpi_os_read_port            
/lib/modules/2.6.38-ck-BKL/build/vmlinux

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