Swati Rawat
100 строки
3.0 KiB
ReStructuredText
100 строки
3.0 KiB
ReStructuredText
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.. meta::
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:description: ROCprofiler-SDK is a tooling infrastructure for profiling general-purpose GPU compute applications running on the ROCm software
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:keywords: ROCprofiler-SDK API reference, ROCprofiler-SDK intercept table, Intercept table API
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.. _runtime-intercept-tables:
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Runtime intercept tables
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=========================
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While tools commonly leverage the callback or buffer tracing services for tracing the HIP, HSA, and ROCTx
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APIs, ROCprofiler-SDK also provides access to the raw API dispatch tables.
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Forward declaration of public C API function
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----------------------------------------------
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All the aforementioned APIs are designed similar to the following sample:
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.. code-block:: cpp
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extern "C"
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{
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// forward declaration of public C API function
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int
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foo(int) __attribute__((visibility("default")));
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}
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Internal implementation of API function
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-----------------------------------------
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.. code-block:: cpp
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namespace impl
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{
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int
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foo(int val)
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{
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// real implementation
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return (2 * val);
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}
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}
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Dispatch table implementation
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-------------------------------
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.. code-block:: cpp
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namespace impl
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{
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struct dispatch_table
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{
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int (*foo_fn)(int) = nullptr;
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};
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// Invoked once: populates the dispatch_table with function pointers to implementation
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dispatch_table*&
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construct_dispatch_table()
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{
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static dispatch_table* tbl = new dispatch_table{};
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tbl->foo_fn = impl::foo;
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// In between, ROCprofiler-SDK gets passed the pointer
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// to the dispatch table and has the opportunity to wrap the function
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// pointers for interception
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return tbl;
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}
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// Constructs dispatch table and stores it in static variable
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dispatch_table*
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get_dispatch_table()
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{
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static dispatch_table*& tbl = construct_dispatch_table();
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return tbl;
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}
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} // namespace impl
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Implementation of public C API function
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-----------------------------------------
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.. code-block:: cpp
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extern "C"
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{
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// implementation of public C API function
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int
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foo(int val)
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{
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return impl::get_dispatch_table()->foo_fn(val);
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}
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}
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Dispatch table chaining
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-------------------------
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ROCprofiler-SDK can save the original values of the function pointers such as ``foo_fn`` in ``impl::construct_dispatch_table()`` and install its own function pointers in its place. This results in the public C API function ``foo`` calling into the ROCprofiler-SDK function pointer, which in turn, calls the original function pointer to ``impl::foo``. This phenomenon is named chaining. Once ROCprofiler-SDK
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makes necessary modifications to the dispatch table, tools requesting access to the raw dispatch table via ``rocprofiler_at_intercept_table_registration`` are provided the pointer to the dispatch table.
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For examples on dispatch table chaining, see `samples/intercept_table <https://github.com/ROCm/rocm-systems/tree/develop/projects/rocprofiler-sdk/samples/intercept_table>`_.
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