There is a problem that happens at random intervals of several minutes or more. The recorded video file is missing a few seconds. Running 'speedometer -r eth0' on the Ubuntu box (Acer C720), and 'top' on the R-Pi, shows that sometimes (always during the network activity of about 6 MB/sec) the kernel thread process 'kworker:0/0' CPU usage goes above 97% and at that time my video/still saving program "r2.py" falls below 1% CPU, even though my process is set to maximum priority with 'nice -20'. The below screen shot was taken at 17:53:43 and sure enough when I review the video stream recorded by the r2.py program with embedded time/date stamp, I see that the video from 17:53:41 to 17:53:45 was not recorded.
How can I prevent kworker from hogging all the CPU when NFS is transferring data? Is there some bandwidth throttling that I can do? Can I limit the damage by reducing the NFS buffer size, so the data is transmitted more frequently but for shorter times? The Pi's kernel is fairly recent:
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[email protected] ~ $ uname -a Linux rp8 3.12.28+ #709 PREEMPT Mon Sep 8 15:28:00 BST 2014 armv6l GNU/Linux
I wonder if it could be related to this bug: https://bugs.launchpad.net/ubuntu/+sour ... ug/1322406