Re: architectures that prevent freezing
Re: architectures that prevent freezing
- Subject: Re: architectures that prevent freezing
- From: Jean-Daniel Dupas <email@hidden>
- Date: Fri, 11 May 2012 18:23:59 +0200
Le 11 mai 2012 à 18:05, Jens Alfke a écrit :
>
> On May 9, 2012, at 7:14 AM, Ph.T wrote:
>
>> . in a pre-emptive OS there should be no freezing;
>> given the new concurrency model
>> that includes the use of the graphics processor GPU
>> to do the system's non-graphics processing,
>
> Well, the GPU can _occasionally_ be used to do some non-graphics work, typically tasks that are highly parallelizable. I’d reckon this happens most often in games, less in general purpose software.
>
>> my current guess is that the freezes happen when
>> something goes wrong in the GPU,
>> and the CPU is just waiting forever .
>> . the CPU needs to have some way of getting control back,
>> and sending an exception message to
>> any of the processes that were affected by the hung-up GPU .
>> . could any of Apple's developers
>> correct this theory or comment on it ?
>
> OS freezes tend to happen when kernel-level code gets into an infinite loop or deadlock. Sure there “should be no freezing” but there should be no bugs either, and that’s never true. (It’s exacerbated by the fact that some 3rd party device drivers need to run in kernel space.)
>
> _Some_ system freezes are due to the GPU completely locking up, usually due to a bug in the GPU vendor’s driver. My understanding is that when this happens it’s not really possible for the GPU to recover without a system reset. The CPU is probably still OK, but that doesn’t do any good if it can’t access the display.
>
> —Jens
While playing with GPU programming, I had a lot of such freeze, and they never locked the CPU. I was always able to connect to my machine though SSH.
Killing the processes that are affected is not enough. You may have to reinitialize the GPU driver. I think this is something Windows is able to do, but not Mac OS X AFAIK.
More info about how it works on Windows can be found here: http://msdn.microsoft.com/en-us/windows/hardware/gg487368
-- Jean-Daniel
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