[mythtv-users] Recording/playing back same file via NFS

Brad DerManouelian myth at dermanouelian.com
Wed Aug 15 14:50:47 UTC 2007


On Aug 15, 2007, at 7:21 AM, Craig Courtney wrote:

>
>
> On 8/13/07, Brad DerManouelian <myth at dermanouelian.com> wrote:
> On Aug 13, 2007, at 2:52 PM, Mark Lehrer wrote:
>
> >
> >> different recordings. Therefore, I have ruled out bandwidth as an
> >> issue. The problem comes is when I try to view something that's
> >> currently being recorded. It happen with both LiveTV and scheduled
> >> recordings. It happens when I'm near the live TV point or if I  
> start
> >> watching something nearing the end of the recording. I get rather
> >> frequent pauses in the video so that it is unwatchable. Like every
> >> 3-5 seconds. This is even with the master backend recording SD and
> >
> >
> > I had a similar problem (though not quite as frequent).  In my case,
> > the write cache would fill up and write out every 30 seconds,  
> freezing
> > the video for an absolutely unbearable couple of seconds.
> >
> > Take a look at the config values /proc/sys/vm/dirty*
> >
> > If I remember correctly, I just had to turn the centisecs down so it
> > wouldn't wait so long to write out the cache.  I'm sorry, power  
> is out
> > at my house or I could shell in and see the exact values I'm using -
> > let me know if you're interested and I'll dig them up in a few  
> hours.
> >
> > Once you find values you like, you can put them in /etc/sysctl.conf.
> >
> > Good luck,
> > Mark
>
> Ahh.. excellent advice and makes sense to what I am experiencing.
> Currently my values look like this:
> [mythtv at mythtv2 vm]$ more dirty_*
> ::::::::::::::
> dirty_background_ratio
> ::::::::::::::
> 10
> ::::::::::::::
> dirty_expire_centisecs
> ::::::::::::::
> 2999
> ::::::::::::::
> dirty_ratio
> ::::::::::::::
> 40
> ::::::::::::::
> dirty_writeback_centisecs
> ::::::::::::::
> 499
>
> I've never touched this stuff before. If you could take a peek at
> yours are and post back, I would really appreciate it.
>
>
> I'm having the exact same problem.  Everything works great as long  
> as I'm not watching a show while it's recording.  Live TV stutters  
> as well as any thing listed in green in the library (signifying  
> it's still recording that show).  I can record 3 shows at once and  
> watch a previously recorded one with out problems.
>
> Where able to find the magic numbers here?

Not yet. I cut my dirty_*_centisecs in half and I see it being a  
little better, but still not great. I'm a little afraid to play with  
the numbers too much since I don't know what side-effects they would  
have. I'm sure they were set to these for a reason. :)

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