USB2.0 Digital TV Tuners - Page 21 - Canadian TV, Computing and Home Theatre Forums
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post #301 of 302 (permalink) Old 2015-11-10, 01:01 PM
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I have two kworld tuners, that are OK at best. Cheapest tuners out there but you get what you pay for. The hauppauge 955q is by far the best atsc tuner I own. And I own quite a few. I have 18 in total lol.

UDL
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post #302 of 302 (permalink) Old 2016-02-14, 06:08 PM Thread Starter
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Thumbs up Hauppauge 950Q Memory Issue and Fix - Linux

I've been using Hauppauge 950Q USB ATSC tuner sticks on my Linux MythTV backend for years and never came across a certain memory-related issue until a few days ago. For the first time ever, during a time of extremely high and sustained load on the MythTV backend system caused by some non-MythTV transcoding I needed to do while lots of other stuff was running, the system load was pegged at full zowie for about two hours on all 6 CPUs while almost all 8GB of RAM was being used (thankfully no swapping). No hardware worries because it is well cooled. Kernel is 4.1.15 non-preemptive.

Anyways, dmesg started showing that the 950Q sticks had been throwing occasional memory panics that were being properly trapped by the kernel. Thankfully those sticks kept on working but I was glad that I had not been trying to record something off them at that time. With some tracing and searching, I discovered a driver setting that I would recommend since it solved the issue above. Here is the appropriate line to add to your /etc/modprobe.conf (or equivalent on your own Linux distro) file:
Code:
options au0828 preallocate_big_buffers=1
options xc5000 no_poweroff=1
The first line is a new (to me) driver option that lays out beforehand some enhanced memory capability for situations of extreme load or for systems with low amounts of RAM. Even though I'm running 8GB of RAM I'm definitely going to keep using the preallocate line. No more au0828 driver panics under extreme loads - problem solved!

That second line is a common Hauppauge 950Q option that has been recommended for years that tells the firmware of those sticks to never let the frontend chip enter "sleep" mode. I'm posting it here in case you might not have known about it.

I hope this is helpful.
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