[mythtv-users] Disk activity at end of recording

[Jack Perveiler]

--- Mark Kundinger <mkundinger at yahoo.com> wrote:

> 
> I also get the recoding-stopping stutter, on a JFS partition, watching
> non-HD content that only uses 15-20% cpu.  I had thought it was
> transcoding or commflaggin starting, but since you don't see that, it
> must just be come voodoo recording completion stuff.
> 
> I am pretty sure (not 100%) that the ringbuffer only refers to watching
> Live TV, not recordings.
> 
> 

> 
> --- Jack Perveiler <perveilerj at yahoo.com> wrote:
> 
> > Hello,
> > 
> > When recordings stop (the recording... not playing back a recording)
> > I get a
> > flurry of disk activity for a second or two... usually enough to
> > cause a
> > stutter for a second if I'm watching a HD recording at the same time.
> >  So if
> > I'm watching a HD recording I can pretty much count on some jitter
> > every half
> > hour as recordings finish.
> > 
> > Some info about my system:
> > 
> > 0) P4 3.0 GHz w/Hyperthreading (HD playback consumes about 70%
> > processor)
> > 1) Tuners are HD-3000 and PVR-500 (usually the HD-3000 and one of the
> > 500
> > tuners is recording)
> > 2) File system is 200 GB XFS LVM local to the machine (combination
> > frontend/backend).  DMA is on (UDMA5).  Output from hdparm:
> > /dev/hda:
> >  multcount    = 16 (on)
> >  IO_support   =  1 (32-bit)
> >  unmaskirq    =  1 (on)
> >  using_dma    =  1 (on)
> >  keepsettings =  0 (off)
> >  readonly     =  0 (off)
> >  readahead    = 256 (on)
> >  geometry     = 30515/255/63, sectors = 490234752, start = 0
> > 
> > 3) No transcoding or commflagging is going on (they're restricted to
> > when I'm
> > sleeping).
> > 
> > So now for my questions:
> > 
> > 1) Does myth do some sort of minimal post-processing when a recording
> > finishes?
> >  Or is this just the OS flushing the remainder of the buffer to disk
> > and
> > closing the file?  Is this maybe something that XFS is just slow at?
> > 
> > 2) I see in one of the frontend setup pages you can set the size of a
> > HD buffer
> > to help "weather backend storms" (or something like that).  Is this
> > one of
> > those cases?  If not, what exactly is that setting for?
> > 
> > Thanks,
> > 
> > --Jack
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> 


I'm glad to see I'm not the only guy seeing the studder then.  Before I
restricted the transcoding/commercial flagging to sleeping hours the problem
was definitely worse, though (which makes sense... hitting a busy disk with
even more traffic).

The setting I was refering to isn't the ringbuffer size... it's something
different.  The way it's described in the help pane on that setup page makes it
sound like a memory buffer of disk traffic.  I'm hoping that's what it is...
enlarging it then would definitely fix my problem.  The trick is to make it
large enough to help but not so large as to cause swapping.  I'll play with it
some this weekend.

Robert Tsai also suggested I check out the mysql log at that time.  I'll check
that out this weekend too.

--Jack




		
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