Returning results directly to Ram Trying to save memory

Accelerated Computing CUDA CUDA Programming and Performance
1

I was wondering, if my code is embarrassingly parallel such that threads do not need to communicate. Can I save GPU shared memory by directing each thread to copy it’s output (single float value) to RAM, will the IO (passing through gpu mem) block/slow/corrupt the work of other threads? How can I achieve that? Asynchronous mem copy?

Example:

Kernel_1:computing…
Kernel_2:computing…
kernel_3:done!
kernel_4:computing…

while kernel instances 1,2 and 4 are still computing copy result of kernal_3 to host/RAM.

Thanks,
Fadhel

2

Yes it is possible. Use streams and asynchroneous copies.

3

I just read more about streams and asynch copy. I think my original question was misleading.

What I meant is having the same kernel call and one of the instances of that kernal copying it’s result back to RAM.

so calling KernelX goes like:

KernelX :computing…

KernelX :computing…

kernelX :done!

kernelX :computing…

and since one of the instances is done computing, can it copy its result to RAM?

Thanks!

4

No I do not think that is possible,

5

Maybe writing to mapped host mem would solve your problem?

6

Use zerocopy to store results directly to host memory if your intention is saving memory on the device. Allocate memory on the host using [font=“Courier New”]cudaHostAlloc()[/font] with the [font=“Courier New”]cudaHostAllocMapped[/font] flag (optionally set [font=“Courier New”]cudaHostAllocWriteCombined[/font] as well if you only ever write to the memory from the GPU side). Then obtain a device pointer for the host memory via [font=“Courier New”]cudaHostGetDevicePointer()[/font]. This device pointer can then be used like any other device pointer, even though the memory resides on the host.