Files
composable_kernel/include/ck/host_utility/kernel_launch.hpp
Estevan Vedovelli f6eb5f0a6a [rocm-libraries] ROCm/rocm-libraries#6379 (commit b38b056)
[ck] Clamp negative kernel execution elapsed time to zero
 (#6379)

## Motivation

hipEventElapsedTime can return a small negative value on Windows when
timing a very fast kernel launch on the null stream. This caused
consumers of launch_and_time_kernel to receive a negative elapsed time,
which they reasonably treat as an error, breaking otherwise-correct
kernel executions.

## Technical Details

After calling hipEventElapsedTime, a clamp is applied in
launch_and_time_kernel before the result is returned, avoiding the
return of a physically impossible elapsed time.

The negative value from hipEventElapsedTime has been observed on
Windows. For kernels that complete in well under a millisecond, the HIP
event timestamps can alias such that the computed difference is a small
negative number (observed: ~-1.78 ms). No HIP error is reported by any
surrounding call (hipEventRecord, hipEventSynchronize, hipGetLastError),
confirming the kernel itself executed successfully.

## Test Plan

- Recompile CK and validate no kernel execution reports a negative
elapsed time during hipTensor tests.
- Pass the CI/CD pre-checking tests for CK.

## Test Result

- All tests passing

## Submission Checklist

- [x] Look over the contributing guidelines at
https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.
2026-04-14 16:15:17 +00:00

306 lines
10 KiB
C++

// Copyright (c) Advanced Micro Devices, Inc., or its affiliates.
// SPDX-License-Identifier: MIT
#pragma once
#ifndef __HIPCC_RTC__
#include <hip/hip_runtime.h>
#include "ck/ck.hpp"
#include "ck/utility/env.hpp"
#include "ck/stream_config.hpp"
#include "ck/host_utility/hip_check_error.hpp"
#include "ck/host_utility/flush_cache.hpp"
namespace ck {
template <typename... Args, typename F>
float launch_and_time_kernel(const StreamConfig& stream_config,
F kernel,
dim3 grid_dim,
dim3 block_dim,
std::size_t lds_byte,
Args... args)
{
#if CK_TIME_KERNEL
if(stream_config.time_kernel_)
{
if(ck::EnvIsEnabled(CK_ENV(CK_LOGGING)))
{
printf("%s: grid_dim {%u, %u, %u}, block_dim {%u, %u, %u} \n",
__func__,
grid_dim.x,
grid_dim.y,
grid_dim.z,
block_dim.x,
block_dim.y,
block_dim.z);
printf("Warm up %d times\n", stream_config.cold_niters_);
}
// warm up
for(int i = 0; i < stream_config.cold_niters_; ++i)
{
kernel<<<grid_dim, block_dim, lds_byte, stream_config.stream_id_>>>(args...);
hip_check_error(hipGetLastError());
}
const int nrepeat = stream_config.nrepeat_;
if(ck::EnvIsEnabled(CK_ENV(CK_LOGGING)))
{
printf("Start running %d times...\n", nrepeat);
}
hipEvent_t start, stop;
hip_check_error(hipEventCreate(&start));
hip_check_error(hipEventCreate(&stop));
hip_check_error(hipDeviceSynchronize());
hip_check_error(hipEventRecord(start, stream_config.stream_id_));
for(int i = 0; i < nrepeat; ++i)
{
kernel<<<grid_dim, block_dim, lds_byte, stream_config.stream_id_>>>(args...);
hip_check_error(hipGetLastError());
}
hip_check_error(hipEventRecord(stop, stream_config.stream_id_));
hip_check_error(hipEventSynchronize(stop));
float total_time = 0;
hip_check_error(hipEventElapsedTime(&total_time, start, stop));
// hipEventElapsedTime can return a small negative value on Windows for a
// very fast kernel. Clamp to zero, as negative elapsed time is never physical.
if(total_time < 0)
total_time = 0;
hip_check_error(hipEventDestroy(start));
hip_check_error(hipEventDestroy(stop));
return total_time / nrepeat;
}
else
{
kernel<<<grid_dim, block_dim, lds_byte, stream_config.stream_id_>>>(args...);
hip_check_error(hipGetLastError());
return 0;
}
#else
kernel<<<grid_dim, block_dim, lds_byte, stream_config.stream_id_>>>(args...);
hip_check_error(hipGetLastError());
return 0;
#endif
}
template <typename... Args, typename F, typename PreProcessFunc>
float launch_and_time_kernel_with_preprocess(const StreamConfig& stream_config,
PreProcessFunc preprocess,
F kernel,
dim3 grid_dim,
dim3 block_dim,
std::size_t lds_byte,
Args... args)
{
#if CK_TIME_KERNEL
if(stream_config.time_kernel_)
{
if(ck::EnvIsEnabled(CK_ENV(CK_LOGGING)))
{
printf("%s: grid_dim {%u, %u, %u}, block_dim {%u, %u, %u} \n",
__func__,
grid_dim.x,
grid_dim.y,
grid_dim.z,
block_dim.x,
block_dim.y,
block_dim.z);
printf("Warm up %d times\n", stream_config.cold_niters_);
}
// warm up
preprocess();
for(int i = 0; i < stream_config.cold_niters_; ++i)
{
kernel<<<grid_dim, block_dim, lds_byte, stream_config.stream_id_>>>(args...);
hip_check_error(hipGetLastError());
}
const int nrepeat = stream_config.nrepeat_;
if(ck::EnvIsEnabled(CK_ENV(CK_LOGGING)))
{
printf("Start running %d times...\n", nrepeat);
}
hipEvent_t start, stop;
hip_check_error(hipEventCreate(&start));
hip_check_error(hipEventCreate(&stop));
hip_check_error(hipDeviceSynchronize());
hip_check_error(hipEventRecord(start, stream_config.stream_id_));
for(int i = 0; i < nrepeat; ++i)
{
preprocess();
kernel<<<grid_dim, block_dim, lds_byte, stream_config.stream_id_>>>(args...);
hip_check_error(hipGetLastError());
}
hip_check_error(hipEventRecord(stop, stream_config.stream_id_));
hip_check_error(hipEventSynchronize(stop));
float total_time = 0;
hip_check_error(hipEventElapsedTime(&total_time, start, stop));
hip_check_error(hipEventDestroy(start));
hip_check_error(hipEventDestroy(stop));
return total_time / nrepeat;
}
else
{
preprocess();
kernel<<<grid_dim, block_dim, lds_byte, stream_config.stream_id_>>>(args...);
hip_check_error(hipGetLastError());
return 0;
}
#else
kernel<<<grid_dim, block_dim, lds_byte, stream_config.stream_id_>>>(args...);
hip_check_error(hipGetLastError());
return 0;
#endif
}
template <typename... Args, typename F, typename PreProcessFunc>
float launch_and_time_kernel_with_preprocess_flush_cache(const StreamConfig& stream_config,
PreProcessFunc preprocess,
F kernel,
dim3 grid_dim,
dim3 block_dim,
std::size_t lds_byte,
Args... args)
{
#if CK_TIME_KERNEL
if(stream_config.time_kernel_)
{
auto run_flush_cache = [&]() { ck::utility::flush_icache(); };
if(ck::EnvIsEnabled(CK_ENV(CK_LOGGING)))
{
printf("%s: grid_dim {%u, %u, %u}, block_dim {%u, %u, %u} \n",
__func__,
grid_dim.x,
grid_dim.y,
grid_dim.z,
block_dim.x,
block_dim.y,
block_dim.z);
printf("Warm up %d times\n", stream_config.cold_niters_);
}
// Warm up
preprocess();
for(int i = 0; i < stream_config.cold_niters_; ++i)
{
kernel<<<grid_dim, block_dim, lds_byte, stream_config.stream_id_>>>(args...);
hip_check_error(hipGetLastError());
}
float total_time = 0, flush_cache_total_time = 0;
const int nrepeat = stream_config.nrepeat_;
// Main timing loop
{
if(ck::EnvIsEnabled(CK_ENV(CK_LOGGING)))
{
printf("Start running %d times...\n", nrepeat);
}
hipEvent_t start, stop;
hip_check_error(hipEventCreate(&start));
hip_check_error(hipEventCreate(&stop));
hip_check_error(hipDeviceSynchronize());
hip_check_error(hipEventRecord(start, stream_config.stream_id_));
for(int i = 0; i < nrepeat; ++i)
{
run_flush_cache();
preprocess();
kernel<<<grid_dim, block_dim, lds_byte, stream_config.stream_id_>>>(args...);
hip_check_error(hipGetLastError());
}
hip_check_error(hipEventRecord(stop, stream_config.stream_id_));
hip_check_error(hipEventSynchronize(stop));
hip_check_error(hipEventElapsedTime(&total_time, start, stop));
hip_check_error(hipEventDestroy(start));
hip_check_error(hipEventDestroy(stop));
}
// Flush cache timing loop
{
if(ck::EnvIsEnabled(CK_ENV(CK_LOGGING)))
{
printf("Profile flush cache %d times...\n", nrepeat);
}
hipEvent_t start, stop;
hip_check_error(hipEventCreate(&start));
hip_check_error(hipEventCreate(&stop));
hip_check_error(hipDeviceSynchronize());
hip_check_error(hipEventRecord(start, stream_config.stream_id_));
for(int i = 0; i < nrepeat; ++i)
{
run_flush_cache();
}
hip_check_error(hipEventRecord(stop, stream_config.stream_id_));
hip_check_error(hipEventSynchronize(stop));
hip_check_error(hipEventElapsedTime(&flush_cache_total_time, start, stop));
hip_check_error(hipEventDestroy(start));
hip_check_error(hipEventDestroy(stop));
}
// Exclude flush cache from result
return (total_time - flush_cache_total_time) / nrepeat;
}
else
{
preprocess();
kernel<<<grid_dim, block_dim, lds_byte, stream_config.stream_id_>>>(args...);
hip_check_error(hipGetLastError());
return 0;
}
#else
kernel<<<grid_dim, block_dim, lds_byte, stream_config.stream_id_>>>(args...);
hip_check_error(hipGetLastError());
return 0;
#endif
}
template <typename... Args, typename F>
float launch_and_time_kernel_flush_cache(const StreamConfig& stream_config,
F kernel,
dim3 grid_dim,
dim3 block_dim,
std::size_t lds_byte,
Args... args)
{
auto preprocess = [&]() {};
return launch_and_time_kernel_with_preprocess_flush_cache(
stream_config, preprocess, kernel, grid_dim, block_dim, lds_byte, args...);
}
} // namespace ck
#endif