CODEWITHSUNDEEP
c++openclgpu
LeMoussel
LeMoussel

Reputation: 5767

With OpenCL, How to get GPU memory usage?

I'm looking for a reliable way to determine current GPU memory usage with OpenCL.

I have found NVidia API: cudaMemGetInfo( size_t* free, size_t* total ) to get free memory and total memory on the current device.

But I'm looking for a solution for AMD and OpenCL. I did not find if there is similar functionality in OpenCL and I don't know if AMD has something equivalent.

I don't want to know how much free memory there is on OpenCL devices before allocating buffers but free memory afer allocating buffers. A priori as indicated in How do I determine available device memory in OpenCL?, With OpenCL, there is no way, and there is no need to know it.

Upvotes: 2

Views: 2903

Answers (1)

mogu
mogu

Reputation: 1119

devices before allocating buffers but free memory afer allocating buffers.

For AMD, perhaps try CL_DEVICE_GLOBAL_FREE_MEMORY_AMD from the cl_amd_device_attribute_query extension - this extension will probably only work with proprietary drivers, though.

In general case, it's impossible, because AFAIK there's no way to know when buffers are allocated (on the device). In this sense OpenCL is higher-level than CUDA. Buffers belong to contexts, not devices. Calling clCreateBuffer() can but doesn't have to allocate any memory on any device; the implementations automatically migrate buffers to device memory before they execute a kernel which needs those buffers, and move them away from the device if they need to free memory for next kernel. Even if you get the free memory of a device, you can't 100% reliably use it to make decisions on whether to run a kernel, because clEnqueueNDRange() doesn't necessarily immediately launch a kernel (it just enqueues it; if there's something else in the queue, it can be delayed), and some other application on the same computer could get scheduled on the GPU in meantime.

If you want to avoid swapping memory, you'll have to make sure 1) your application is the only one using the GPU, 2) for each of your kernels, total buffer arguments size must be <= GLOBAL_MEM_SIZE.

Upvotes: 4

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