[mythtv-users] High mythbackend CPU usage during DVB-T recording (Australia)

[Anthony Giggins]

On 16 July 2013 18:38, Christian Hack <christian at hack.id.au> wrote:

>
> On 16 July 2013 06:12, HP-mini <blm-ubunet at slingshot.co.nz> wrote:
>
>> On Mon, 2013-07-15 at 14:20 +1000, Christian Hack wrote:
>> >
>> >
>> > On 15 July 2013 08:36, Kenni Lund <kenni at kelu.dk> wrote:
>> >
>> >         Den 15/07/2013 00.28 skrev "Kenni Lund" <kenni at kelu.dk>:
>> >
>> >         >
>> >         > Also, do you use get your EPG from EIT? If not, you should
>> >         be able to save some CPU cycles by disabling EIT.
>> >         >
>> >         > FYI, the upcoming MythTV 0.27 contains multiple
>> >         optimizations which should lower the CPU utilization when
>> >         recording (see for example ticket #12250, #11252 or #11255)
>> >         Sorry, that should have been #11250, not #12250.
>> >
>> >         Best regards
>> >         Kenni
>> >
>> > Gave 0.26 a whirl last night and after fighting a number of issues
>> > which were a pain (mysql timezone issue, mythweb broken,
>> > mythtv-database upgrade failed, password issue in config.xml), I have
>> > 0.26 running. Unfortunately that also seems to have mostly broken the
>> > PiP which had previously worked fairly well in 0.25 with VDPAU :( .
>> > Just when I needed it for Tour de France and the Ashes...
>> >
>> > Anyway, with 2 HD recordings that I had running CPU usage dropped from
>> > what would normally be around 130%-140%-150% to around 90%. Still
>> > fairly high in my opinion but definitely improved noticeably.
>> >
>> > EPG comes from a scraper. EIT is off on all tuners and also even on
>> > the channels themselves and I've never used it here since it's (well
>> > was) a bit rubbish.
>>
>> Old *buntus are likely to cause HDD partition alignment issues (on big
>> disks) that could cost ~20% disk throughput.
>>
>>
> Brand new install of 12.04. Even then I get 50-60MByte/sec throughput when
> copying from disk to disk. So recording a few MByte/sec should be no issue.
> It shouldn't cause high CPU usage in the backend. Maybe IO waiting.
>
>
>> Is the high CPU use caused by one or more CPU cores stuck at 100%?
>> Are you auto-running mythcommflagging/transcoding?
>
>
> No. As mentioned mythcommflagging is set to only one thread that is
> separate to the the mythbackend's CPU usage and killing it makes no
> difference. No transcoding but again that would be a different process.
>
>
>> Are any high CPU usage tasks named mythlogserver? there could be
>> several..
>> This seems to go rogue if mythbackend logging options are not right.
>> Do the BE & mythlogserver logs & their contents appear okay?
>> This high CPU usage is with no FE playback right ?
>>
>>
> No mythlogserver processes going crazy - I've not seent that issue. Again
> this wouldn't explain mythbackend using a lot of CPU to record. The high
> CPU usage is with recording only with or without mythfrontend doing
> anything. The 4% usage in the original post is typical and that was playing
> a HD stream. VDPAU is working well for me with very little CPU required.
>
>
>> Check your mythtv-backend upstart job script against the mythtv wiki
>> page.
>> AFAIK mythbuntu has a FE wrapper script that re-spawns the FE if it
>> crashes.
>>
>>
> Check what exactly? I'm using the standard mythbuntu setup. I don't really
> see how or why this could be an issue. Yes mythbuntu respawns the frontend.
>
>
>> I don't recall seeing your graphics h/w except for iCPU/IGP.
>> VDPAU video decode/playback is only possible on nVidia GPU (all recent)
>> & some (& only some) AMD when using FOSS radeon driver.
>> VA-API is viable option on some intel GPU & the latest haswell could
>> eventually be a match for VDPAU.
>>
>>
> nVidia GT440 running VDPAU very successfully and as noted working fine.
> Again, not a mythbackend issue.
>
> Christian
>
>
> Sounds tuner related, I'm running a HDhomerun also in AU also on mythbuntu
12.04 (0.26-fixes) and I'm not seeing these issues, the other thing you
might want to confirm is if your mysql database is running on ext4 as there
are optimisations required there or reinstall with ext3 instead.

Cheers,

Anthony
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