Hi Svein,

I have reread about spec and find I may have some misunderstand about svm 
atomic, we have not fit the requirement for CL_MEM_SVM_ATOMIC now. The SVM are 
just support and as well as the 2.0 atomics. It seems that SVM atomic has some 
very strict requires to device and we haven’t implement that. Sorry for the 
wrong information.

Thanks
Xiuli

From: Beignet [mailto:beignet-boun...@lists.freedesktop.org] On Behalf Of Pan, 
Xiuli
Sent: Monday, March 28, 2016 1:08 PM
To: Svein Berge <sve...@pvv.org>
Cc: beignet@lists.freedesktop.org
Subject: Re: [Beignet] Low latency io

Hi Svein,

You will need some drm and intel linux kernel that later then 2016, Jan( I did 
not know the expect commit or date that they support what we need for SVM).
And for llvm3.8 you only need a simple patch for pipe built-in to clang, you 
can download it from http://reviews.llvm.org/D15603.

If you find anything wrong please feel free to ask, the OpenCL 2.0 is still 
under developed and we are welcomed you to have a try to see if there is any 
bug.

Thanks
Xiuli

From: Beignet [mailto:beignet-boun...@lists.freedesktop.org] On Behalf Of Svein 
Berge
Sent: Saturday, March 26, 2016 5:48 PM
To: Pan, Xiuli <xiuli....@intel.com<mailto:xiuli....@intel.com>>
Cc: beignet@lists.freedesktop.org<mailto:beignet@lists.freedesktop.org>
Subject: Re: [Beignet] Low latency io

Hello Xiuli,

that’s great news! I tested the OCL20 branch in January. I don’t think it 
supported SVM atomics then, and I couldn’t get the OCL20 branch to build when I 
tried again last week. I will make a new attempt next week. You mention the 
need for an llvm patch to build it - could you tell me which patch that is?

I have some question about the old style way, is the kernel need to be running 
all the time as the io changes the memory? And do some response to it at a low 
latency?

That is correct.

And could you explain the idea about how “invalidate a cache line from the 
kernel” can help with you requires?

The idea is to write a loop in opencl which polls a memory location and flushes 
that memory location from cache so it will be read from system memory each 
time. But my understanding of the caching and coherence mechanisms involved is 
not good. Anyway, this point should be moot if you now support SVM atomics.

Cheers,

Svein

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