[mythtv-users] Mythbackend causing high load

Christian Hack christianh at edmi.com.au
Mon Jul 3 09:24:54 UTC 2006


> -----Original Message-----
> From: mythtv-users-bounces at mythtv.org 
> [mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Mario Bernard
> Sent: Monday, 3 July 2006 6:18 PM
> To: Discussion about mythtv
> Subject: Re: [mythtv-users] Mythbackend causing high load
> 
> 
> >It appears the cause is due to fragmentation in the file system. Once
> >reiserfs is severely fragmented it starts to take huge 
> amounts of CPU to
> >search for free blocks. 
> 
> >Do you record two programs at once often? Apparently this is 
> what causes
> >the most fragmentation. So depending on how badly your file system is
> >fragmented will depend on how much free space you're going to have to
> >keep available at all times. With a ~500gb drive, I would 
> recommend you
> >keep between 50-60gb free at all times. 
> 
> I record with 3 tuners heavily.
> 
> >I finally got in touch with the reiserfs guys and it looks 
> like this may
> >be a bug, so hopefully we can help them track it down and 
> get it fixed. 
> 
> The actual version is 3, or not ?
> When will the version 4 be released, or will the problem also 
> exist in this version.
> 

For the record I have very similar problems also. I record from two DVB
cards often and I get massive load when I get to around 22-23GB free on a
300GB ResierFS partition. A while back it used to start around 16-17GB.
While recording I start to see IOBOUND errors, and if I'm lucky enough to
have a top session open, I can see the load jump up over 20.0 at which point
pretty much everything grinds to a halt.

As soon as I delete a few files, the problem immediately goes away and it
starts recording fine again.

Maybe it's time to look for a new FS that's a bit better. Can ReiserFS be
defragged?

CH




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