[PlanetCCRMA] Fwd: Re: [LAU] Balance between performance and noise

[Fernando Lopez-Lezcano]

Hey, I thought I would repost this here (after all we are all striving 
for good performance at low latencies). I was having problems with xruns 
in my laptop: I could only get xrun free behavior if I actually turned 
off the cpuspeed daemon (lost a lot of time on it) - just setting the 
governor to "Performance Mode" would not help.

Turning off pci and pci express power management (but not power 
management for the CPU) in the BIOS seems to have made all the 
difference. This may be premature because I have not done a full scale 
test yet but my first impression is that it works.

-- Fernando

-------- Original Message --------
Subject: 	Re: [LAU] Balance between performance and noise
Date: 	Thu, 09 Dec 2010 15:54:47 -0800
From: 	Fernando Lopez-Lezcano <nando at ccrma.Stanford.EDU>
To: 	Robin Gareus <robin at gareus.org>
CC: 	linux-audio-user at lists.linuxaudio.org


On 12/09/2010 12:10 PM, Robin Gareus wrote:
>  On 12/09/2010 06:39 PM, rosea.grammostola wrote:
>>  On 12/09/2010 06:35 PM, Robin Gareus wrote:
>>>  On 11/27/10 13:11, Arnold Krille wrote:
>>>
>>>>  Set ther cpu-governor to performance (so it doesn't switch
>>>>  frequencies which
>>>>  produces xruns) but reduce the maximum allowed frequency.
>>>>
>>>  what kernel are you running?
>>>
>>
>>>     2.6.33.7-rt29
>>>
>>
>>  That one ^
>>
>>  You tested it with yoshimi, hammond or other heavy patches? Foo-yc20 ?
>
>  different toolset here, but I can go from naught to 16 jconvolvers,
>  csound, fluidsynth, ardour&   jamin in a few seconds. causing the CPU
>  usage to jump up and change freq w/o x-runs.
>
>  ..what does cause problems here is FSBus frequency scaling, I've
>  disabled that in the BIOS.

Turns out that there are two parameters in my laptop's BIOS (Lenovo
T510) that can disable both pci and pci express power management.

I'll be darned! Guess what? The xruns are gone! Like magic!! Just on a
preliminary test (I don't have all the hardware I would need here) but
running with the "Ondemand" governor.

This is a _golden_ tip. Thanks much!

-- Fernando
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