The command_submit in the sycl::info::event_profiling, submits the whole code or just the parallel-for?

Question

I try to analyze the execution time of my function on device. I read this link: https://docs.oneapi.com/versions/latest/dpcpp/iface/event.html but I did not find in the documentation any information about sycl::info::event_profiling, which let me to understand what they correspond exactly. I mean, the command_start, command_end, command_submit. for example: This is a part of my code, kernel,

auto event = gpuQueue.submit([&](sycl::handler &h) {
                //local copy of fun
                auto f = fun;
                sycl::accessor in_accessor(in_buffer, h, sycl::read_only);
                sycl::accessor out_accessor(out_buffer, h, sycl::write_only);
                h.parallel_for(n_item, [=](sycl::id<1> index) {
                    out_accessor[index] = f(in_accessor[index]);
                });
            });
            event.wait();
            auto end_overall = std::chrono::system_clock::now();
            cl_ulong submit_time = event.template get_profiling_info<
                    cl::sycl::info::event_profiling::command_submit>();
            cl_ulong start_time = event.template get_profiling_info<
                    cl::sycl::info::event_profiling::command_start>();
            cl_ulong end_time = event.template get_profiling_info<
                    cl::sycl::info::event_profiling::command_end>();

which I want to understand the cl::sycl::info::event_profiling::command_submit, submits the whole code or just submits the parallel-for?

Answer 1

It is a bit clearer on the SYCL 2020 specification:

• command_submit is the timestamp of the command group submission to the SYCL runtime.
• command_start is the timestamp of the actual parallel for starting
• command_end is the timestamp of the parallel for completion

So, your kernel execution time in the device is command_start - command_end, whereas the total processing time for a command group (i.e. with the potential copies, runtime overhead, etc) is command_submit - command_end.