[mythtv-commits] Ticket #11756: Slow reads and writes

[MythTV]

#11756: Slow reads and writes
-------------------------------------+-------------------------------------
 Reporter:  Craig Treleaven          |           Type:  Bug Report -
  <ctreleaven@…>                     |  General
   Status:  new                      |       Priority:  minor
Milestone:  unknown                  |      Component:  Ports - OSX
  Version:  0.26-fixes               |       Severity:  medium
 Keywords:                           |  Ticket locked:  0
-------------------------------------+-------------------------------------
 Recently upgraded from 0.25-fixes to 0.26-fixes.  After a few days, the
 logs are showing thousands of warning and error messages related to slow
 reads and writes.  The backend has high CPU usage (compared to 0.25) while
 recording and becomes very slow to respond to keystrokes.  There are
 frequent pauses while trying to playback recordings, to the point of being
 unwatchable.

 mythcommflag and, to a much lesser extent, mythfrontend logs show
 thousands of lines like the following:

 {{{
 /opt/local/var/log/mythtv.26/mythcommflag.20130816020139.12091.log:2013-08-15
 22:17:31.811969 I [12091/20539] Decoder ringbuffer.cpp:1098 (WaitForAvail)
 - RingBuf(/Volumes/Theatre/Mythical/1411_20130816020000.mpg): Waited 8.0
 seconds for data
 ...
 /opt/local/var/log/mythtv.26/mythcommflag.20130816020139.12091.log:2013-08-15
 22:17:42.038103 W [12091/20539] Decoder ringbuffer.cpp:1035
 (WaitForReadsAllowed) -
 RingBuf(/Volumes/Theatre/Mythical/1411_20130816020000.mpg): Taking too
 long to be allowed to read..
 /opt/local/var/log/mythtv.26/mythcommflag.20130816020139.12091.log:2013-08-15
 22:17:42.038121 E [12091/20539] Decoder ringbuffer.cpp:1040
 (WaitForReadsAllowed) -
 RingBuf(/Volumes/Theatre/Mythical/1411_20130816020000.mpg): Took more than
 10 seconds to be allowed to read, aborting.
 }}}

 mythbackend logs are showing thousands of write-related messages like the
 following:

 {{{
 /opt/local/var/log/mythtv.26/mythbackend.20130816124946.12592.log:2013-08-16
 08:56:01.045786 W [12592/33539] TFWWrite ThreadedFileWriter.cpp:500
 (DiskLoop) - TFW(/Volumes/Theatre/Mythical/1051_20130816125200.mpg:121):
 write(65424) cnt 527 total 37107628 -- took a long time, 4063 ms
 /opt/local/var/log/mythtv.26/mythbackend.20130816124946.12592.log:2013-08-16
 08:56:05.761917 W [12592/33539] TFWWrite ThreadedFileWriter.cpp:500
 (DiskLoop) - TFW(/Volumes/Theatre/Mythical/1051_20130816125200.mpg:121):
 write(58844) cnt 406 total 29148648 -- took a long time, 4072 ms
 /opt/local/var/log/mythtv.26/mythbackend.20130816124946.12592.log:2013-08-16
 08:56:09.875380 W [12592/33539] TFWWrite ThreadedFileWriter.cpp:500
 (DiskLoop) - TFW(/Volumes/Theatre/Mythical/1051_20130816125200.mpg:121):
 write(65424) cnt 501 total 35242856 -- took a long time, 4110 ms
 /opt/local/var/log/mythtv.26/mythbackend.20130816124946.12592.log:2013-08-16
 08:56:12.923309 W [12592/33539] TFWWrite ThreadedFileWriter.cpp:500
 (DiskLoop) - TFW(/Volumes/Theatre/Mythical/1051_20130816125200.mpg:121):
 write(65424) cnt 576 total 40110740 -- took a long time, 2949 ms
 /opt/local/var/log/mythtv.26/mythbackend.20130816124946.12592.log:2013-08-16
 08:56:17.062006 W [12592/33539] TFWWrite ThreadedFileWriter.cpp:500
 (DiskLoop) - TFW(/Volumes/Theatre/Mythical/1051_20130816125200.mpg:121):
 write(160364) cnt 470 total 31585880 -- took a long time, 4094 ms
 /opt/local/var/log/mythtv.26/mythbackend.20130816124946.12592.log:2013-08-16
 08:56:21.738661 W [12592/33539] TFWWrite ThreadedFileWriter.cpp:500
 (DiskLoop) - TFW(/Volumes/Theatre/Mythical/1051_20130816125200.mpg:121):
 write(65424) cnt 357 total 24079980 -- took a long time, 4053 ms
 }}}

 The machine is a Mac Mini Core2 Duo running OS X 10.7.5 with a Firewire
 400-connected drive for recording storage.  Under 0.25 there was no
 noticeable issue.  (Before a fix went into 0.25 in Oct 2012, however,
 there was much the same problem.)

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Ticket URL: <http://code.mythtv.org/trac/ticket/11756>
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