[mythtv-users] CPU performance governor vs disabling AMD Cool n Quiet

[Greg Oliver]

On Sat, Oct 23, 2010 at 1:48 PM, faginbagin <mythtv at hbuus.com> wrote:
> First some background to my questions, and to hopefully help anyone who
> encounters the same problem:
>
> I "upgraded" my sister's mythtv box, replacing an older ECS mobo/AMD Sempron
> 32 bit single core CPU with an ASUS M3N78 PRO mobo/AMD Athlon X2 4850e dual
> core cpu. The "new" computer used to be my mbe/fe and had worked fine with
> two HVR-1600 cards. But with her PVR-150 and a HD-5500, she's been having
> trouble with the PVR-150 choking after a few days of recording. I think the
> problem was due to me enabling AMD Cool n Quiet in the BIOS (it was disabled
> by default). She's been sensitive to fan noise, so although it wasn't
> enabled when the computer was mine, I thought I would enable it for her.
>
> The problem manifested itself with an incomplete recording after 2-7 days of
> uptime, followed by completely failed recording attempts plus dmesg output
> filled with messages like:
> ivtv0: DMA TIMEOUT 00000001 0
>
> Turning on debug output in the ivtv driver showed these two messages of
> interest at the time recording began to fail:
> ivtv0:  warn: DMA ERROR 00000003 00000000 00000013 0
> ivtv0:  warn: DMA ERROR 00000003 00000000 00000011 2
>
> The only way to get the PVR-150 to work was to reboot. Stopping the
> mythbackend, unloading/reloading ivtv and restarting mythbackend didn't
> clear the problem.
>
> I think I have solved the problem by changing the CPU frequency governor
> from ondemand to performance. It's only bee a week, so I'm going to give it
> another week, and if I get no more failed recordings, I will declare success
> and make the change permanent. My questions are:

I did not have any issues like this, but I did find that the cpu was
underpowered while governed to powersave (which it almost always was)
and the osd activated, etc..  I solved it by locking core 4 to
1800MHz, and using taskset to bind init to processors 0-2 (which makes
all processes spawned from init (almost the whole system)) run on cpu
cores 1,2,3 and then assigning mythfrontend to core 4.  I no longer
get "skips or jerks" when I activate the OSD, but it sounds like this
may apply in your situation as well.

I was also given some links that would allow to let mythtv alter the
cpu frequency as well, but I have not gotten that granular yet (but I
plan to as soon as I deploy this machine to the rest of the house)..

> Should I change the BIOS setting to disable AMD Cool n Quiet or do something
> to make the CPU frequency governor = performance at boot time?
>
> Is there a difference, any advantage using one method over the other, any
> gotchas?
>
> Also, has anyone seen a difference in the performance of the M3N78's IGP
> (nVidia 8300) with these various tweaks?
>
> I ask because the performance of the IGP has been disappointment with Cool n
> Quiet enabled and the ondemand governor. I never used the IGP since I've
> still got an SD TV. The IGP is barely able to play 1080i content with the
> VDPAU slim profile. Such content is unwatchable with VDPAU normal. I'll get
> a chance to see if it's any better with the performance governor tomorrow.
> If not, it looks like I'll have to get her a GT 220 GPU.