[mythtv-users] Mythvideo performance

[Brian Wood]

On Jun 15, 2006, at 9:39 PM, Ryan Steffes wrote:

>
>
> Hmm, I have an nForce2 chipset, but I am getting;  ivtv0:  
> Unreasonably low latency timer, setting to 64 (was 32)
>
>
> lspci shows:
> 00:09.0 IDE interface: nVidia Corporation MCP2A IDE (rev a3) (prog- 
> if 8a [Master SecP PriP])
>         Subsystem: Micro-Star International Co., Ltd.: Unknown  
> device 5700
>         Flags: bus master, 66Mhz, fast devsel, latency 0
>         I/O ports at f000 [size=16]
>         Capabilities: [44] Power Management version 2
>
> 00:0b.0 IDE interface: nVidia Corporation nForce2 Serial ATA  
> Controller (rev a3) (prog-if 85 [Master SecO PriO])
>         Subsystem: Micro-Star International Co., Ltd.: Unknown  
> device 5700
>         Flags: bus master, 66Mhz, fast devsel, latency 0, IRQ 11
>         I/O ports at 09f0 [size=8]
>         I/O ports at 0bf0 [size=4]
>         I/O ports at 0970 [size=8]
>         I/O ports at 0b70 [size=4]
>         I/O ports at d000 [size=16]
>         I/O ports at d400 [size=128]
>         Capabilities: [44] Power Management version 2
>
>
> Does that mean my hard drives are ALWAYS getting interrupted?  The  
> command 'setpci -v -s 00: 09.0 latency_timer=b0' didn't cause the  
> output of lspci -v to change.
>

Glad to see you figured out what your problem was.

Some motherboards do not seem to allow for changing the latency of  
the drive controllers and/or don't properly read it out.

That "zero" probably doesn't mean anything, and more likely means  
that it has a high priority. In any case there's nothing you can do.  
The nForce is a good chipset so I wouldn't worry. Many motherboards  
set all latencies to 32, I think IVTV was being overly cautious.

Your mobo may allow you to change the default latencies in the BIOS,  
but this would not be likely to improve performance in your case.

Still it's good to know about how the latency values work. With a VIA  
chipset I was unable to make 2 recordings at once, and re-setting  
things let me make 4 at ones with a couple of commflag jobs running  
as well. I think manual intervention osusually required only on  
poorly designed boards though.