[mythtv] Ticket #10414: HDHomeRun: Bad Recordings (was: Bad Recordings - Choppy Playback)

Marc Randolph mrand at pobox.com
Sun Mar 11 00:44:52 UTC 2012

On Sat, Mar 10, 2012 at 10:41 AM, Daniel Kristjansson
<danielk at cuymedia.net> wrote:
> On Fri, 2012-03-09 at 13:17 -0500, Tom Lichti wrote:
>> On Fri, Mar 9, 2012 at 12:44 PM, Derek Atkins <warlord at mit.edu> wrote:
>> > Tom Lichti <tom at redpepperracing.com> writes:
>> I'm trying to rule that out. I don't think it's network or interrupts,
>> I have all Gig-E networking, and the backend is actually a server,
>> Dell Poweredge SC1435, so the only thing I can see is it being the
>> disk. I'll try putting a storage group on another disk and test that
>> and report back.
> I doubt it is the disk. 0.25 dynamically resizes it's buffer up to
> about 128 MB per recording vs the user specified buffer that defaulted
> to 9.6MB in 0.24.
> I was able to reproduce a problem with old firmware using udp
> streaming, but with newer firmware employing rtp streaming I
> can not reproduce the issue. I'm also not seeing the high CPU
> usage reported. I see about 15% CPU usage with two recordings.
> Can you take a look at this:
>  http://www.cyberciti.biz/faq/linux-tcp-tuning/
> And tell me if increasing the rmem_max helps?
> libmythhdhomerun tries to increase the socket buffer
> on startup, but perhaps the rmem_max is set low on
> your system? Mine is set to 131071000.

Wow.  http://fasterdata.es.net/fasterdata/host-tuning/linux/ seems to
suggest that values 10x smaller would be about good enough for a 10
Gbps network, and that going overboard actually hurts performance.
Wonder which site is right.


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