Bug 8100

Created attachment 10553 [details]
lspci -vvv on my macbook

Created attachment 10554 [details]
dmesg on 2.6.21-rc2 with dynticks

Reply-To: akpm@linux-foundation.org

On Wed, 28 Feb 2007 09:34:10 -0800
bugme-daemon@bugzilla.kernel.org wrote:

> http://bugzilla.kernel.org/show_bug.cgi?id=8100
> 
>            Summary: dynticks makes ksoftirqd1 use unreasonable amount of cpu
>                     time
>     Kernel Version: 2.6.21-rc2
>             Status: NEW
>           Severity: low
>              Owner: johnstul@us.ibm.com
>          Submitter: jkarlson@cc.hut.fi
> 
> 
> Most recent kernel where this bug did *NOT* occur:
> any kernel without dynticks
> 
> Distribution:
> Debian etch with linux-2.6.21-rc{2,1}
> 
> Hardware Environment: 
> Macbook core2 with bios emulation
> 
> Software Environment:
> The problem is obvious when listening to shoutcast stream with kmplayer and 
> artsd via wi-fi with  wpa (wpa_supplicant)
> 
> Problem Description:
> ksoftirqd1 uses ~30% cpu-time (by top) no other symptoms, while
> without dyntikcs cpu-load in similar circumstances is negligible.
> This might be a dynticks feature rather than bug.
> 
> Steps to reproduce:
> Just watch the top, if the bug is reproducible, probably just booting should 
> suffice.
> 
> ------- You are receiving this mail because: -------
> You are on the CC list for the bug, or are watching someone who is.

Is there a way to reproduce this with a simpler software environment ?

	tglx

Mocp doesn't give nearly as bad results 2% of cpu time, just idling gives ~1%, 
which is still higher than on uneffected kernels.

Seems that just mplayer on local files suffices to give ~30%.

Just noted wi-fi was partially binary ndiswrapper, sorry about that - still 
reproducible without it (not loaded).

MPlayer dev-SVN-rUNKNOWN-4.1.2 (C) 2000-2007 MPlayer Team
CPU: Intel(R) Core(TM)2 CPU         T7200  @ 2.00GHz (Family: 6, Model: 15, 
Stepping: 6)
CPUflags:  MMX: 1 MMX2: 1 3DNow: 0 3DNow2: 0 SSE: 1 SSE2: 1
Compiled with runtime CPU detection.
Can't open joystick device /dev/input/js0: No such file or directory
Can't init input joystick
mplayer: could not connect to socket
mplayer: No such file or directory
Failed to open LIRC support. You will not be able to use your remote control.

Playing kompressormusic_-_VITAMINS_ARE_GOOD.mp3.
Audio file file format detected.
==========================================================================
Opening audio decoder: [mp3lib] MPEG layer-2, layer-3
AUDIO: 44100 Hz, 2 ch, s16le, 128.0 kbit/9.07% (ratio: 16000->176400)
Selected audio codec: [mp3] afm: mp3lib (mp3lib MPEG layer-2, layer-3)
==========================================================================
AO: [alsa] 48000Hz 2ch s16le (2 bytes per sample)
Video: no video

Created attachment 10653 [details]
a working config

Seems that this is at least partially configuration issue added some timer
stuff to config on 2.6.21-rc2, which pacified ksoftirqd. Now kernel seems to
work for this bug.

Created attachment 10654 [details]
the dysfunctional config

This won't work

Reply-To: pavel@ucw.cz

Hi!

> bugme-daemon@bugzilla.kernel.org wrote:
> 
> > http://bugzilla.kernel.org/show_bug.cgi?id=8100
> > 
> >            Summary: dynticks makes ksoftirqd1 use unreasonable amount of cpu
> >                     time
> >     Kernel Version: 2.6.21-rc2
> >             Status: NEW
> >           Severity: low
> >              Owner: johnstul@us.ibm.com
> >          Submitter: jkarlson@cc.hut.fi
> > 
> > 
> > Most recent kernel where this bug did *NOT* occur:
> > any kernel without dynticks
> > 
> > Distribution:
> > Debian etch with linux-2.6.21-rc{2,1}
> > 
> > Hardware Environment: 
> > Macbook core2 with bios emulation
> > 
> > Software Environment:
> > The problem is obvious when listening to shoutcast stream with kmplayer and 
> > artsd via wi-fi with  wpa (wpa_supplicant)
> > 
> > Problem Description:
> > ksoftirqd1 uses ~30% cpu-time (by top) no other symptoms, while
> > without dyntikcs cpu-load in similar circumstances is negligible.
> > This might be a dynticks feature rather than bug.

top lies. top has always lied, now it lies more. Do not trust top.
RESOLVED/INVALID?

							Pavel

If top lies, in this case, it also does a good job in convincing the cpu fan to 
add cycles. I can get ps readings, if you want.

> If top lies, in this case, it also does a good job in convincing the cpu fan
> to 
> add cycles. I can get ps readings, if you want.

I diffed your good and bad configs. It changes way too many options at
once, so it's hard to tell what might be the cause of the problem.

Can you work from the good one and identify the option, which makes
things actually bad ?

Thanks

	tglx

CONFIG_HIGH_RES_TIMERS=y

Unsetting this alone will make the problem reappear.

> CONFIG_HIGH_RES_TIMERS=y
> 
> Unsetting this alone will make the problem reappear.

What happens, if you switch off CONFIG_NO_HZ too ?

	tglx

Unsetting CONFIG_NO_HZ fixes the problem but also deselects 
CONFIG_TICK_ONESHOT.

> Unsetting CONFIG_NO_HZ fixes the problem but also deselects 
> CONFIG_TICK_ONESHOT.

Right, this depends on each other.

Is the problem still there with -rc3 ?

	tglx

yes, the problem is still present in 2.6.21-rc3

Created attachment 10934 [details]
trace-it output requested

bugzilla does not accept files bigger than 10000kiB, sorry.

> Created an attachment (id=10934)
>  --> (http://bugzilla.kernel.org/attachment.cgi?id=10934&action=view)
> trace-it output requested
> 
> bugzilla does not accept files bigger than 10000kiB, sorry.

No problem bz2 is fine. Somthing went wrong with the tracing. It's only
event trace.

Bah. I missed the line:

	system("echo 1 > /proc/sys/kernel/mcount_enabled");

New version at:
http://tglx.de/private/tglx/2.6.21-rc4-trace/trace-it.c

Sorry. Can you please retry ?

Thanks,

	tglx

The new trace can be found at 
http://users.tkk.fi/~jkarlson/tavaraa/trace-with-mplayer.gz

4MiB unpacked...

> The new trace can be found at 
> http://users.tkk.fi/~jkarlson/tavaraa/trace-with-mplayer.gz
> 
> 4MiB unpacked...

Good. This gives more info. Please try the attached patch.

Thanks

	tglx

Created attachment 10935 [details]
Patch to fix the problem

Gack. It discards the patch in the mail.

Tried the patch, works on 2.6.21-rc4 with dynticks without hrtimer. It should 
fix the problem afaik.

The patch fixing this bug is included in 2.6.21-rc5.