ywang103-amd
9b562c0e58
* initial commit * add csv support extraction for non kernel selection mode * add --kernel-trace for rocprofiler-sdk mode * make non kernel selective mode runnable * make kernel selection work with -k * remove upper case of arg hint * update documentation * display same kernel name at only one place and merge instruction id with same obj id as well as offset * remove kernel name's display for single kernel selection * change log added --------- Co-authored-by: Fei Zheng <44449748+feizheng10@users.noreply.github.com>
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76 行
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.. meta::
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:description: ROCm Compute Profiler: using PC sampling
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:keywords: ROCm Compute Profiler, PC sampling
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********************************************
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Using PC sampling in ROCm Compute Profiler
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********************************************
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Program Counter (PC) sampling service for GPU profiling is a profiling technique that periodically samples the program counter during the GPU kernel execution to understand code execution patterns and hotspots.
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ROCm Compute Profiler supports Host Trap PC sampling and Stochastic (Hardware-Based) PC sampling.
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Host Trap PC sampling is enabled for AMD Instinct MI200 series and later
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accelerators. Stochastic (hardware-based) PC sampling is enabled for
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AMD Instinct MI300 series and later accelerators. Stochastic PC sampling provides additional information that tells whether a sampled wave issued an instruction for a particular PC. It also provides the reason
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for not issuing the instruction (stall reason). This type of information is
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particularly useful for understanding stalls during the kernel execution. The PC sampling can be used with profiling and analysis options.
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---------------------
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Profiling options
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---------------------
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For using profiling options for PC sampling the configuration needed are:
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* ``--pc-sampling-method``: Should be either ``stochastic`` or ``host_trap``, (DEFAULT: stochastic)
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* ``--pc-sampling-interval``: For stochastic sampling, the interval is in cycles. The finest granularity is 1 cycle. For ``host_trap`` sampling, the interval is in microsecond (DEFAULT: 1048576). The interval should be the power of 2. You are recommended try starting from 1048576, and lowering until reaching 65536.
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**Sample command:**
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.. code-block:: shell
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$ rocprof-compute profile -n pc_test -b 21 --no-roof --pc-sampling-method stochastic --pc-sampling-interval 1048576 -VVV -- target_app
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-----------------------
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Analysis options
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-----------------------
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For using analysis options for PC sampling the configuration needed are:
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* ``--pc-sampling-sorting-type``: ``offset`` or ``count``. The default option is ``offset``. ``offset`` is an assembly instruction offset in the code object.
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**Sample command:**
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.. code-block:: shell
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$ rocprof-compute analyze -p workloads/pc_test/MI300A_A1/ -b 21 -k 0 --pc-sampling-sorting-type offset
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**Sample output:**
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Selecting single kernel host trap PC sampling:
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.. image:: ../data/pc_sampling/pc_sampling_host_trap_single_kernel.png
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:align: left
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:alt: Host trap PC sampling snapshot
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Selecting single kernel stochastic PC sampling:
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.. image:: ../data/pc_sampling/pc_sampling_stochastic_single_kernel.png
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:align: left
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:alt: Stochastic PC sampling snapshot
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If you don't filter by kernel, the output will fall back to the original data from ``rocprofv3`` csv output for all the kernels:
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.. image:: ../data/pc_sampling/pc_sampling_no_kernel_filtering.png
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:align: left
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:alt: Host trap PC sampling snapshot no_kernel_filtering
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Selecting single kernel sorting by PC count:
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.. image:: ../data/pc_sampling/pc_sampling_sort_by_count.png
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:align: left
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:alt: Host trap PC sampling sorting snapshot
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.. note::
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* PC sampling feature is currently in BETA version. To enable PC sampling, you have to explicitly enable it with block index 21.
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* PC sampling now only shows assembly instructions collected in our record of pc samples and not all instructions of compiled code are represented.
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* To associate PC sampling info back to HIP source code, you need to build the profiling target app with ``-g`` to keep the symbols. Otherwise, PC sampling info will be only associated with assembly lines.
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