John, I tried your patches out and everything worked dandy until I began a compile. A few minutes later I started getting "IOBOUND - blocking in ThreadedFileWriter::Write()" messages and the dmesg started reporting lost data. As soon as I stopped the compile both the IOBOUND messages and the buffer overrun messages stopped. The thing is, the buffer reports never reported a buffer over 6% full.
I was compiling myth (niced), which is was mostly cached with ccache so I'm assuming the problem was actually that ccache was initiating a lot of disk activity (the system was 40% idle throughout). This must also have been a case of priority inversion since the compile was niced. Are writes to the buffer somehow blocked during the syncs? Or does the write disk access just monopolize the CPU too long? Admitedly, compiling with ccache enabled is a pretty tough test for MythTV, but it's the only way I can reliably get buffer overruns normally. BTW I set the PCI latency timers to 60, which normally avoids starving any particular device on the bus. -- Daniel Here's is the important portion of the log: [EMAIL PROTECTED] mythtv $ mythbackend Starting up as the master server. .... 2004-12-12 20:26:18.633 Started recording "National Lampoon's Christmas Vacation" on channel: 3004 on cardid: 4, sourceid 3 2004-12-12 20:26:19.148 Changing from None to RecordingOnly 2004-12-12 20:26:19.554 Maximum signal strength detected: 81% after 0 msec wait 2004-12-12 20:26:19.668 Desired program #1 not found in PAT. Substituting program #3 2004-12-12 20:26:26.650 Found changes in the todo list. 2004-12-12 20:26:28.653 Scheduled 267 items in 2.0 seconds. 2004-12-12 20:28:26.456 /dev/video34 ringbuf avg 0.0183095% max 0.3479% samples17044 2004-12-12 20:30:56.588 /dev/video34 ringbuf avg 0.0183105% max 0.823975% samples 20167 2004-12-12 20:33:27.087 /dev/video34 ringbuf avg 0.0183105% max 0.860596% samples 20217 2004-12-12 20:35:58.614 /dev/video34 ringbuf avg 0.0268591% max 1.24512% samples 20355 2004-12-12 20:38:30.153 /dev/video34 ringbuf avg 0.027269% max 1.22681% samples20356 2004-12-12 20:41:02.626 /dev/video34 ringbuf avg 0.0385751% max 1.97754% samples 20482 2004-12-12 20:43:36.724 /dev/video34 ringbuf avg 0.0601566% max 2.16064% samples 20700 2004-12-12 20:46:11.362 /dev/video34 ringbuf avg 0.0762239% max 2.6001% samples20773 2004-12-12 20:49:03.308 /dev/video34 ringbuf avg 0.0972768% max 3.22266% samples 20883 2004-12-12 20:49:35.187 IOBOUND - blocking in ThreadedFileWriter::Write() 2004-12-12 20:49:37.101 IOBOUND - blocking in ThreadedFileWriter::Write() 2004-12-12 20:49:39.252 IOBOUND - blocking in ThreadedFileWriter::Write() 2004-12-12 20:51:41.644 /dev/video34 ringbuf avg 0.12151% max 5.51147% samples 21026 2004-12-12 20:54:14.689 /dev/video34 ringbuf avg 0.0463993% max 1.57471% samples 20559 2004-12-12 20:56:48.308 /dev/video34 ringbuf avg 0.0547135% max 1.79443% samples 20636 ....
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