在CUDA中动态分配的共享内存。 执行配置

Question

What does by this Nvidia means?

Ns is of type size_t and specifies the number of bytes in shared memory that is dynamically allocated per block for this call in addition to the statically allocated memory; this dynamically allocated memory is used by any of the variables declared as an external array as mentioned in __shared__ ; Ns is an optional argument which defaults to 0;

Size of shared memory in my GPU is 48kB. For example I want to run 4 kernels at the same time, every of them uses 12kB of shared memory.

In order to do that, should I call kernek this way

kernel<<< gridSize, blockSize, 12 * 1024 >>>();

or should the third argument be 48 * 1024 ?

Answer 1

Ns in a size in bytes. If you want to reserve 12kB of shared memory you would do 12*1024*1024 .

I doubt you want to do this. Ns value is PER BLOCK . So it is the amount of shared memory per block executing on the device. I'm guessing you'd like to do something around the lines of 12*1024*1024/number_of_blocks;

Kernel launching with concurrency: If as mentioned in a comment, you are using streams there is a fourth input in the kernel launch which is the cuda stream.

If you want to launch a kernel on another stream without any shared memory it will look like:

kernel_name<<<128, 128, 0, mystream>>>(...);

but concurrency is a whole different issue.