Sun, Peng
49 linhas
2.6 KiB
Markdown
49 linhas
2.6 KiB
Markdown
# HIP Bugs
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<!-- toc -->
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- [Errors related to undefined reference to `__hcLaunchKernel__***__grid_launch_parm**](#errors-related-to-undefined-reference-to-hclaunchkernel__grid_launch_parm)
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- [Application hangs after a hipLaunchKernel call](#what-if-i-see-application-hangs-after-a-hiplaunchkernel-call)
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- [What is the current limitation of HIP Generic Grid Launch method?](#what-is-the-current-limitation-of-hip-generic-grid-launch-method)
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<!-- tocstop -->
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### Errors related to undefined reference to `__hcLaunchKernel__***__grid_launch_parm**
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Some common code practices may lead to hipcc generating a error with the form :
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undefined reference to `__hcLaunchKernel__ZN15vecAddNamespace6vecAddIidEEv16grid_launch_parmPT0_S3_S3_T_
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To workaround, try:
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- Avoid calling hcLaunchKernel from a function with the __host__ attribute
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__host__ MyFunc(…) {
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hipLaunchKernel(myKernel, …)
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- Avoid use of static with kernel definition:
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static __global__ MyKernel
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- Avoid defining kernels in anonymous namespace
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namespace {
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__global__ MyKernel …
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- Avoid calling member functions
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If hipLaunchKernel takes parameters that request explicitly memcpy, then it will cause application hang.
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Reason is that the hipLaunchKernel macro locks the stream.
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If kernel paramters are actually function calls which invoke other hip apis (i.e. memcpy) to the same stream, then deadlock occurs.
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To workaround, try:
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Move the function calls so they occur outside the hipLaunchKernel macro, store results in temps, then use the tems inside the kernel.
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```
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// Example pseudo code causing system hang:
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// "bottom[0]->gpu_data()" calls hipMemcpy() implicitly and using the same stream, cause deadlock condition.
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hipLaunchKernel(HIP_KERNEL_NAME(LRNComputeDiff),dim3(CAFFE_GET_BLOCKS(n_threads)), dim3(CAFFE_HIP_NUM_THREADS), 0, 0, n_threads,
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bottom[0]->gpu_data());
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// Move "gpu_data()" ouside of hipLaunchKernel to avoid hang.
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auto bot_gpu_data = bottom[0]->gpu_data();
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hipLaunchKernel( LRNComputeDiff, dim3(CAFFE_GET_BLOCKS(n_threads)), dim3(CAFFE_HIP_NUM_THREADS), 0, 0, n_threads,
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bot_gpu_data);
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```
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### What is the current limitation of HIP Generic Grid Launch method?
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1. __global__ functions cannot be marked as static or put in an unnamed namespace i.e. they cannot be given internal linkage (this would clash with __attribute__((weak)));
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2. using the macro based dispatch mechanism i.e. hipLaunchKernel* only works for functions that take no more than 20 arguments (this limit can be increased up to 126, and is temporary until we can enable C++14 mode and use variadic generic lambdas); no such limitation applies do dispatching directly through grid_launch. |