Re: [Xen-users] PCI passthrough partial success

[Andy Burns <lists.xensource.com@xxxxxxxxxxxxxx>]

On 02/07/2008 23:27, Christopher Isip wrote:

> I have mythbackend running in an Ubuntu-Hardy domU with a Centos 5.1 
> dom0.  Here are the settings that work for me:
I found a bug in the saa7123 tuner driver where it was mapping too large 
an mmio area, so patched that, then found it was sharing an interrupt 
with devices from dom0, so added pollirq, now I  have an infrequent DMA 
panic.
>     kernel /boot/xen.gz-3.2 swiotlb=256 noirqdebug
I had been searching around for swiotlb info, I'll try your settings 
tomorrow ...
is noirqdebug preferred instead of pollirq? I was getting the "nobody 
cared, IRQ disable dmesg"
> extra = "swiotlb=force 
hmm, my domU kernel crashed immediately when I trye swiotlb=force

> #It probably wont hurt to increase the domU's scheduling priority, run 
> this in dom0:
> xm sched-credit -d Ubuntu-Mythtv -w 512
So far I've not noticed performance being a problem, recording 3 
concurrent streams from a single tuner takes under 10% of one core of a 
Q9450 cpu.
> I would suggest having the Mythtv backend not do any transcoding or 
> commflagging.  Instead, create slave mythtv backends without tuners and 
> have them do the transcode and commflagging.  This effectively 
> compartmentalizes the commflagger and transcoder so that the main mythtv 
> backend will not drop frames when writing to the disk.
Good suggestion, though again I've been amazed how much faster this 
backend is at transcoding than my "old" P4 combined frontend/backend.
> My only problem with the system is I get dma timeout errors in dmesg.  
> These were present even in a nonxen setup, so I think it is related to 
> my hardware and ivtv.
hmm, mine are panics, not just dmesg, but I never saw them when the 
tuners were in the  non-xen machines.
> Hope that helps.  I am still trying to find ways to optimize the 
> mythbackend domU so If you have any ideas, please let me know.
Thanks,  will do.



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