[ltp] Temperature increase after S2Ram

[Henrique de Moraes Holschuh]

On Mon, 08 Jul 2013, Paul Bolle wrote:
> On Mon, 2013-07-08 at 00:07 -0300, Henrique de Moraes Holschuh wrote:
> > On Sun, 07 Jul 2013, Paul Bolle wrote:
> > > Somehow it seems powertop triggers Heisenbug behavior! If the second
> > > core is apparently stuck at 2 GHz, and I start powertop to see what's
> > > going on, the second core will again drop down to 800 MHz, eventually.
> > > But quitting powertop makes the second core jump to 2 GHz again (judging
> > > by /proc/cpuinfo's output, that is).
> > > 
> > > That is strange! So let's assume for now that I see patterns that just
> > > aren't there. Ie, this needs more testing on my side.
> > 
> > Nah, let's assume 3.10 is borked.  Please check whether the latest 3.9.x
> > works well for you...
> 
> I hope to do so shortly.
> 
> > > > and turbostat
> > >     $ sudo ./turbostat -S
> > >     No invariant TSC
> > 
> > I see.  Can powertop show idle states on that box?  If it does, keep an eye
> > on them.
> 
> But powertop (at least) masks the problem: while powertop is running
> CPU1 (the second core that seems to be stuck at going 2 GHz) does drop
> back to 800 MHz.
> 
> Another curious thing, perhaps related: acpi_cpufreq's refcount wraps
> after offlining and onlining this core a few times:
>     $ cat /proc/modules | grep acpi_cpufreq
>     acpi_cpufreq 19612 18446744073709551609 - Live 0xffffffffa0465000 (F)
>     mperf 12607 1 acpi_cpufreq, Live 0xffffffffa0418000 (F)
> 
> 18446744073709551609 equals (2 ^ 64) - 7. I guess I've offlined that
> core seven times now.

Yep, that looks like a bug alright.  Can you file it with relevant
information in bugzilla.kernel.org?  Call it "acpi_cpufreq's refcount wraps
after offlining and onlining a core a few times".

I know there are a few fixes for intel idle, acpi cpufreq, and a few others
floating around the merge window.  Right now, it is either bissect, or wait
for 3.10.1 to get the brown-paperbag fixes.

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh