[mythtv-users] ringbuffer errors?

[Karl Newman]

On Thu, Jan 2, 2014 at 7:29 AM, Jeff Breitner <jtbreitner.lists at gmail.com>wrote:

>
> Have you looked at what you are using for a kernel IO scheduler?
>
> I think there may be some unpleasant interaction with the backend thread
> writer and kernel IO scheduling in deadline or cfq.  Noop seems to be the
> only way I can avoid having those kinds of messages along with complaints
> about waiting 100ms (or more) for video.
>
> Even though XFS does a good job preventing fragmentation, once the file
> system gets north of 85% capacity, the performance starts to drop off.
>  Does your LiveTV storage fit within 85% capacity?
>
> Finally, has your bios done something stupid and moved your sata drives to
> legacy ata?  I found that a bios flash to fix a different flaw changed it,
> and only when I was chasing a red herring on this issue did I notice that
> ncq was turned off (cat /sys/block/sda/device/queue_depth == 1 ... which is
> disabled).
>
>
Hmm... I wonder if this would help the issue I'm having. I used to be able
to do disk-intensive operations (copy/move multi-GB files, etc.) and myth
would never skip a beat. Then I upgraded my platform a couple years ago.
Now I have to ionice anything or the frontend will pause/skip, and I'm sure
the backend will as well (I haven't stressed it while recording). I checked
that same variable and sure enough, it's 1. dmesg shows that NCQ is
available, but disabled (depth 0/32). I seem to recall seeing that early on
when I first got my new mobo (Asus P8H67-M PRO) and thought "Oh, it shows
NCQ so it must be working." I'll have to check my BIOS settings and make
sure they're set for AHCI (and make sure the AHCI kernel module is loaded
as well). According to the mobo manual the default is IDE (i.e., legacy)
mode. I don't remember specifically changing that setting so that's
probably my problem.

Anyway, thanks for the tip!

Karl
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