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Re: [Qemu-devel] Re: [Try2][PATCH] Initial implementation of a mpeg1 lay


From: François Revol
Subject: Re: [Qemu-devel] Re: [Try2][PATCH] Initial implementation of a mpeg1 layer2 streaming audio driver.
Date: Tue, 16 Nov 2010 21:10:22 +0100

Le 16 nov. 2010 à 20:33, Anthony Liguori a écrit :

> On 11/16/2010 01:22 PM, Andreas Färber wrote:
>> Am 15.11.2010 um 22:53 schrieb François Revol:
>> 
>>> I'm still having a hard time getting sound to work reliably in Haiku guests 
>>> regardless the output or emulated card. OTH it works perfectly in 
>>> VirtualBox with almost no cpu overhead. If anyone has a clue...
>>> It might be related to the use of RDTSC as primary time source, still it's 
>>> the same in vbox.
>> 
>> Did you check the time drift command line options? Iirc Gleb needed some 
>> hacks for timer-related issues on Windows.
> 
> Time drift correction is only applicable to the RTC and PIT and deals with 
> catching up the periodic timers.

Except Haiku, just like BeOS 15 years ago (Linux didn't invent it) does 
tickless, so it likely has other side effects from the PIT emulation...
It should be possible to use IO-APIC for timers now, and it seems vbox has it 
enabled, but I don't remember if the code is totally working yet.

IIRC the HPET timer support also is about running timers for now, not as a 
timesource.

> The issue with the TSC as a time source is that it skips around during CPU 
> migration.  The easiest way to work around this is to simply pin your guest 
> to a single physical CPU (assuming you're using KVM).

Isn't there a POSIX API now for pinning down processes on cpus ?
Hmm seems pthread_attr_setaffinity_np is non portable...
Can't seem to find an equivalent on OSX...
Oh wait, maybe this:
http://developer.apple.com/library/mac/#releasenotes/Performance/RN-AffinityAPI/

I'll see if I can make use of this.

>>> (does [KVM] even work on OSX ?)
>> 
>> No.

Won't even try to write a kext for it anyway.

François.




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