[mythtv-commits] Re: Ticket #551: blocking in ThreadedFileWriter

[MythTV]

#551: blocking in ThreadedFileWriter
-----------------------+----------------------------------------------------
 Reporter:  anonymous  |        Owner:  danielk 
     Type:  defect     |       Status:  assigned
 Priority:  major      |    Milestone:  0.19    
Component:  mythtv     |      Version:  head    
 Severity:  medium     |   Resolution:          
-----------------------+----------------------------------------------------
Changes (by danielk):

  * status:  new => assigned
  * owner:  ijr => danielk

Old description:

> SVN for the last week has had some major issues with blocking in file
> writing.  In a test system that has not had any changes except SVN
> versions of Myth, we've seen blocking very frequently.  The problem
> typically comes up when recording two HD shows or viewing one and
> recording another.  This had worked fine, including recording 4 HD
> streams and viewing another using SVN from three weeks ago.  When
> failures occured, we tried increasing the ring buffer size 4 times the
> default without any help.  The system is not out of memory either.  Doing
> a top shows the mythbackend running at 60%-100% CPU usage, which I've
> never seen before.  The system load (via the w command or top) has shown
> the load between 6-14 at times, when nothing else except system processes
> were running.  Stopping the backend returns the system back to a normal
> load.  DMA has been checked on the drives, so it's not this (And since
> nothing changed since it worked fine.)
>
> I think the system load jumping so high may be a sign of a threading
> problem for file writing?
>
> We've disabled the eit-parser since this was what I've noticed the most
> experimental changes in lately but it had no effect.
>
> The end result are video files with major corruption.  Over a 5 minute
> span, only 2-5 second clips every 5-30 seconds are saved.

New description:

 SVN for the last week has had some major issues with blocking in file
 writing.  In a test system that has not had any changes except SVN
 versions of Myth, we've seen blocking very frequently.  The problem
 typically comes up when recording two HD shows or viewing one and
 recording another.  This had worked fine, including recording 4 HD streams
 and viewing another using SVN from three weeks ago.  When failures
 occured, we tried increasing the ring buffer size 4 times the default
 without any help.  The system is not out of memory either.  Doing a top
 shows the mythbackend running at 60%-100% CPU usage, which I've never seen
 before.  The system load (via the w command or top) has shown the load
 between 6-14 at times, when nothing else except system processes were
 running.  Stopping the backend returns the system back to a normal load.
 DMA has been checked on the drives, so it's not this (And since nothing
 changed since it worked fine.)

 I think the system load jumping so high may be a sign of a threading
 problem for file writing?

 We've disabled the eit-parser since this was what I've noticed the most
 experimental changes in lately but it had no effect.

 The end result are video files with major corruption.  Over a 5 minute
 span, only 2-5 second clips every 5-30 seconds are saved.

Comment:

 I couldn't reproduce this initially, but I can now..

 I believe the only change was that I upgraded from Linux 2.6.12 to
 2.6.13...

 I'll take a look at this tomorrow.

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Ticket URL: <http://cvs.mythtv.org/trac/ticket/551>
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