Re: High latency on /sys/class/thermal

["Tiago Simões Batista" <tiagosbatista@gmail.com>]

On Sat, 11 Apr 2009 23:16:11 +0100
Tiago Simões Batista <tiagosbatista@gmail.com> wrote:

> Sorry about the noise, by brain was stopped when I sent the last mail,
> please ignore the From address, it is wrong!
> 
> On Sat, 11 Apr 2009 12:14:16 -0700
> Andrew Morton <akpm@linux-foundation.org> wrote:
> 
> > (cc linux-acpi)
> > 
> > On Sat, 11 Apr 2009 15:56:12 +0100 "Tiago Sim__es Batista"
> > <tiagosbatista@gmail.com> wrote:
> > 
> > > Hi all
> > > 
> > > Yesterday, I recompiled my kernel (git + tuxonice)
> > > v2.6.30-rc1-1002-gac91f91, there were a couple of issues, the main
> > > one is ilustrated bellow.
> > > 
> > > I am not familiar with the kernel code, but if you give me some
> > > pointers, I will be glad to investigate this further
> > > 
> > > $time cat /sys/class/thermal/thermal_zone0/temp 
> > > 34000
> > > 
> > > real	0m6.613s
> > > user	0m0.000s
> > > sys	0m0.001s
> > > 
> > 
> > Is this a regression?  Was 2.6.29 OK?
> > 
> > Thanks.
> 
> My last kernel was fine:
> 
> $ time cat /sys/class/thermal/thermal_zone0/temp 
> 48000
> 
> real	0m0.007s
> user	0m0.001s
> sys	0m0.007s
> 
> 
> I also forgot to add some information about my kernels...
> 
> The good one is 2.6.29 + tuxonice as it was the day after the 2.6.29
> kernel was released.
> 
> The bad one is a pull from linus tree on april the 9th plus tuxonice
> on the same day
> 
> from git (hope this helps):
> $ git describe v2.6.29-tiago2-ice
> v2.6.29-836-g00492ed
> $ git describe v2.6.30-rc1-tiago1-ice
> v2.6.30-rc1-1002-gac91f91
> 
> 
> If tuxonice is a suspect, I will be glad to remove it and recompile.
> If I have the time later this weekend, and nothing was found, I will
> try to bisect this.
> 

Here are some results from the bisect:
The metric I used to mark a revision as good/bad was
$ time for ((i =0; i < 100; i++)); do
      cat /sys/class/thermal/thermal_zone0/temp > /dev/null; 
  done

The bad ones take forever, i never even finished one bad run. The good
ones take about half a second.

When I checked out revisions v2.6.29-148-g33526a5 and
v2.6.29-159-g8a3f257, it took almost 2 secons to run the command, so I
think some of the latency my have been introduced around these. Yet, I
still marked them as good.

The resut was:
478c6a43fcbc6c11609f8cee7c7b57223907754f is first bad commit
witch is a merge. I am out of ideas...

I forgot to ask, am I the only one experiencing this? I am using a
TravelMate 4000 with the intel graphics chip, can anyone reproduce this?
If no one can reproduce this, I can still test a vanilla kernel to
remove TOI from the equation!

Tiago


Below is the bisect log:
$ git bisect log
git bisect start
# bad: [ac91f917d7ed7d1ebe14532ee137fcd759b4406d] Merge branch 'all' into all-tuxonice
git bisect bad ac91f917d7ed7d1ebe14532ee137fcd759b4406d
# good: [178a426510a901d9335f39d3391ae5e8628a36d1] Merge branch 'tuxonice' into all-tuxonice
git bisect good 178a426510a901d9335f39d3391ae5e8628a36d1
# good: [fdf9c9979a355916433262ea5e5e64bed5def86e] V4L/DVB (10465): dsbr100: Add few lost mutex locks.
git bisect good fdf9c9979a355916433262ea5e5e64bed5def86e
# good: [edbd606c4671fcd439164c8d63e896044d706156] Staging: wlan-ng: Replace WLAN_LOG_ERROR() with printk()
git bisect good edbd606c4671fcd439164c8d63e896044d706156
# good: [3516c6a8dc0b1153c611c4cf0dc4a51631f052bb] Merge git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging-2.6
git bisect good 3516c6a8dc0b1153c611c4cf0dc4a51631f052bb
# bad: [3989203290fba6fdf6bc4825fbf6526e1bf17977] Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6
git bisect bad 3989203290fba6fdf6bc4825fbf6526e1bf17977
# bad: [d7ca6f8cdffa5765e486edb3dada9121fba8e6aa] Merge branch 'for-linus' of git://git.o-hand.com/linux-rpurdie-backlight
git bisect bad d7ca6f8cdffa5765e486edb3dada9121fba8e6aa
# good: [3b4dadf05d177289c279c50030c7c75e004952bb] Merge branch 'acpi_enforce_resources' into release
git bisect good 3b4dadf05d177289c279c50030c7c75e004952bb
# bad: [32fb6c17566ec66de87324a834c7776f40e35e78] Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6
git bisect bad 32fb6c17566ec66de87324a834c7776f40e35e78
# good: [45e36c1666aa6c8b0c538abcf984b336184d8c3f] Merge git://git.kernel.org/pub/scm/linux/kernel/git/lethal/sh-2.6
git bisect good 45e36c1666aa6c8b0c538abcf984b336184d8c3f
# good: [33526a53600ac887d100e3c9b4be3637ac8ae3a5] Merge branch 'x2apic' into release
git bisect good 33526a53600ac887d100e3c9b4be3637ac8ae3a5
# good: [c542aadeb4700bc316834d862d52ba3d2664f13a] panasonic-laptop: Fix autoloading
git bisect good c542aadeb4700bc316834d862d52ba3d2664f13a
# bad: [478c6a43fcbc6c11609f8cee7c7b57223907754f] Merge branch 'linus' into release
git bisect bad 478c6a43fcbc6c11609f8cee7c7b57223907754f
# good: [15065531c1c5902775ae3ade24eb37d0e688353b] toshiba-acpi: remove MAINTAINERS entry
git bisect good 15065531c1c5902775ae3ade24eb37d0e688353b
# good: [8a3f257c704e02aee9869decd069a806b45be3f1] Merge branch 'misc' into release
git bisect good 8a3f257c704e02aee9869decd069a806b45be3f1