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fwill
Journeyman III

Problem with CL_MEM_ALLOC_HOST_PTR in Linux

Hello,

I Create buffer object with CL_MEM_ALLOC_HOST_PTR in Linux, it is said in program guide that memory object is created in device memory, but i found it is created in host memory, as in Windows.

Where is the memory object location, in device memory or in host memory?

PS, I use Radeon HD 6930 card, driver is 12.2. Host OS is Fedora 14 (x86_64), and AMD sdk is 2.6.

Thanks a lot!

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jeff_golds
Staff
Staff

Re: Problem with CL_MEM_ALLOC_HOST_PTR in Linux

The buffer is created in host memory, but if you try to bind the buffer to a kernel, then the buffer will be migrated to the device.

You can use host memory for source and destination of copies without worrying about migration.

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fwill
Journeyman III

Re: Problem with CL_MEM_ALLOC_HOST_PTR in Linux

Thanks for your answer!

That means zero copy is not supported in Linux, is it right?

Then how about Windows, if create buffer object with CL_MEM_ALLOC_HOST_PTR in Windows, is zero copy supported?

Thanks!

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jeff_golds
Staff
Staff

Re: Problem with CL_MEM_ALLOC_HOST_PTR in Linux

Zero copy is supported whenever VM is supported.  See the "driver version" in the device info query.

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