Callback tracing services#
Overview#
Callback tracing services provide immediate callbacks to a tool on the current CPU thread when a given event occurs.
For example, when tracing an API function, e.g. hipSetDevice, callback tracing invokes a user-specified callback
before and after the traced function executes on the thread which is invoking the API function.
Subscribing to Callback Tracing Services#
During tool initialization, tools configure callback tracing via the rocprofiler_configure_callback_tracing_service
function:
rocprofiler_status_t
rocprofiler_configure_callback_tracing_service(rocprofiler_context_id_t context_id,
rocprofiler_callback_tracing_kind_t kind,
rocprofiler_tracing_operation_t* operations,
size_t operations_count,
rocprofiler_callback_tracing_cb_t callback,
void* callback_args);
The kind parameter is a high-level specifier of which service to trace (also known as a “domain”).
Domain examples include, but are not limited to, the HIP API, the HSA API, and kernel dispatches.
For each domain, there are (often) various “operations”, which can be used to restrict the callbacks
to a subset within the domain. For domains which correspond to APIs, the “operations” are the functions
which compose the API. If all operations in a domain should be traced, the operations and operations_count
parameters can be set to nullptr and 0, respectively. If the tracing domain should be restricted to a subset
of operations, the tool library should specify a C-array of type rocprofiler_tracing_operation_t and the
size of the array for the operations and operations_count parameter.
rocprofiler_configure_callback_tracing_service will return an error if a callback service for given context
and given domain is configured more than once. For example, if one only wanted to trace two functions within
the HIP runtime API, hipGetDevice and hipSetDevice, the following code would accomplish this objective:
{
auto ctx = rocprofiler_context_id_t{};
// ... creation of context, etc. ...
// array of operations (i.e. API functions)
auto operations = std::array<rocprofiler_tracing_operation_t, 2>{
ROCPROFILER_HIP_RUNTIME_API_ID_hipSetDevice,
ROCPROFILER_HIP_RUNTIME_API_ID_hipGetDevice
};
rocprofiler_configure_callback_tracing_service(ctx,
ROCPROFILER_CALLBACK_TRACING_HIP_RUNTIME_API,
operations.data(),
operations.size(),
callback_func,
nullptr);
// ... etc. ...
}
But the following code would be invalid:
{
auto ctx = rocprofiler_context_id_t{};
// ... creation of context, etc. ...
// array of operations (i.e. API functions)
auto operations = std::array<rocprofiler_tracing_operation_t, 2>{
ROCPROFILER_HIP_RUNTIME_API_ID_hipSetDevice,
ROCPROFILER_HIP_RUNTIME_API_ID_hipGetDevice
};
for(auto op : operations)
{
// after the first iteration, will return ROCPROFILER_STATUS_ERROR_SERVICE_ALREADY_CONFIGURED
rocprofiler_configure_callback_tracing_service(ctx,
ROCPROFILER_CALLBACK_TRACING_HIP_RUNTIME_API,
&op,
1,
callback_func,
nullptr);
}
// ... etc. ...
}
Callback Tracing Callback Function#
Rocprofiler-sdk callback tracing callback functions have the signature:
typedef void (*rocprofiler_callback_tracing_cb_t)(rocprofiler_callback_tracing_record_t record,
rocprofiler_user_data_t* user_data,
void* callback_data)
The record parameter contains the information to uniquely identify a tracing record type and has the
following definition:
typedef struct rocprofiler_callback_tracing_record_t
{
rocprofiler_context_id_t context_id;
rocprofiler_thread_id_t thread_id;
rocprofiler_correlation_id_t correlation_id;
rocprofiler_callback_tracing_kind_t kind;
uint32_t operation;
rocprofiler_callback_phase_t phase;
void* payload;
} rocprofiler_callback_tracing_record_t;
The underlying type of payload field above is typically unique to a domain and, less frequently, an operation.
For example, for the ROCPROFILER_CALLBACK_TRACING_HIP_RUNTIME_API and ROCPROFILER_CALLBACK_TRACING_HIP_COMPILER_API,
the payload should be casted to rocprofiler_callback_tracing_hip_api_data_t* – which will contain the arguments
to the function and (in the exit phase) the return value of the function. The payload field will only be a valid
pointer during the invocation of the callback function(s).
The user_data parameter can be used to store data in between callback phases. It is a unique for every
instance of an operation. For example, if the tool library wishes to store the timestamp of the
ROCPROFILER_CALLBACK_PHASE_ENTER phase for the ensuing ROCPROFILER_CALLBACK_PHASE_EXIT callback,
this data can be stored in a method similar to below:
void
callback_func(rocprofiler_callback_tracing_record_t record,
rocprofiler_user_data_t* user_data,
void* cb_data)
{
auto ts = rocprofiler_timestamp_t{};
rocprofiler_get_timestamp(&ts);
if(record.phase == ROCPROFILER_CALLBACK_PHASE_ENTER)
{
user_data->value = ts;
}
else if(record.phase == ROCPROFILER_CALLBACK_PHASE_EXIT)
{
auto delta_ts = (ts - user_data->value);
// ... etc. ...
}
else
{
// ... etc. ...
}
}
The callback_data argument will be the value of callback_args passed to rocprofiler_configure_callback_tracing_service
in the previous section.
Callback Tracing Record#
The name of a tracing kind can be obtained via the rocprofiler_query_callback_tracing_kind_name function.
The name of an operation specific to a tracing kind can be obtained via the rocprofiler_query_callback_tracing_kind_operation_name
function. One can also iterate over all the callback tracing kinds and operations for each tracing kind via the
rocprofiler_iterate_callback_tracing_kinds and rocprofiler_iterate_callback_tracing_kind_operations functions.
Lastly, for a given rocprofiler_callback_tracing_record_t object, rocprofiler-sdk supports generically iterating over
the arguments of the payload field for many domains.
As mentioned above, within the rocprofiler_callback_tracing_record_t object,
an opaque void* payload is provided for accessing domain specific information.
The data types generally follow the naming convention of rocprofiler_callback_tracing_<DOMAIN>_data_t,
e.g., for the tracing kinds ROCPROFILER_BUFFER_TRACING_HSA_{CORE,AMD_EXT,IMAGE_EXT,FINALIZE_EXT}_API,
the payload should be casted to rocprofiler_callback_tracing_hsa_api_data_t*:
void
callback_func(rocprofiler_callback_tracing_record_t record,
rocprofiler_user_data_t* user_data,
void* cb_data)
{
static auto hsa_domains = std::unordered_set<rocprofiler_buffer_tracing_kind_t>{
ROCPROFILER_BUFFER_TRACING_HSA_CORE_API,
ROCPROFILER_BUFFER_TRACING_HSA_AMD_EXT_API,
ROCPROFILER_BUFFER_TRACING_HSA_IMAGE_EXT_API,
ROCPROFILER_BUFFER_TRACING_HSA_FINALIZER_API};
if(hsa_domains.count(record.kind) > 0)
{
auto* payload = static_cast<rocprofiler_callback_tracing_hsa_api_data_t*>(record.payload);
hsa_status_t status = payload->retval.hsa_status_t_retval;
if(record.phase == ROCPROFILER_CALLBACK_PHASE_EXIT && status != HSA_STATUS_SUCCESS)
{
const char* _kind = nullptr;
const char* _operation = nullptr;
rocprofiler_query_callback_tracing_kind_name(record.kind, &_kind, nullptr);
rocprofiler_query_callback_tracing_kind_operation_name(
record.kind, record.operation, &_operation, nullptr);
// message that
fprintf(stderr, "[domain=%s] %s returned a non-zero exit code: %i\n", _kind, _operation, status);
}
}
else if(record.phase == ROCPROFILER_CALLBACK_PHASE_EXIT)
{
auto delta_ts = (ts - user_data->value);
// ... etc. ...
}
else
{
// ... etc. ...
}
}
Sample rocprofiler_iterate_callback_tracing_kind_operation_args#
int
print_args(rocprofiler_callback_tracing_kind_t domain_idx,
uint32_t op_idx,
uint32_t arg_num,
const void* const arg_value_addr,
int32_t arg_indirection_count,
const char* arg_type,
const char* arg_name,
const char* arg_value_str,
int32_t arg_dereference_count,
void* data)
{
if(arg_num == 0)
{
const char* _kind = nullptr;
const char* _operation = nullptr;
rocprofiler_query_callback_tracing_kind_name(domain_idx, &_kind, nullptr);
rocprofiler_query_callback_tracing_kind_operation_name(
domain_idx, op_idx, &_operation, nullptr);
fprintf(stderr, "\n[%s] %s\n", _kind, _operation);
}
char* _arg_type = abi::__cxa_demangle(arg_type, nullptr, nullptr, nullptr);
fprintf(stderr, " %u: %-18s %-16s = %s\n", arg_num, _arg_type, arg_name, arg_value_str);
free(_arg_type);
// unused in example
(void) arg_value_addr;
(void) arg_indirection_count;
(void) arg_dereference_count;
(void) data;
return 0;
}
void
callback_func(rocprofiler_callback_tracing_record_t record,
rocprofiler_user_data_t* user_data,
void* cb_data)
{
if(record.phase == ROCPROFILER_CALLBACK_PHASE_EXIT &&
record.kind == ROCPROFILER_CALLBACK_TRACING_HIP_RUNTIME_API &&
(record.operation == ROCPROFILER_HIP_RUNTIME_API_ID_hipLaunchKernel ||
record.operation == ROCPROFILER_HIP_RUNTIME_API_ID_hipMemcpyAsync))
{
rocprofiler_iterate_callback_tracing_kind_operation_args(
record, print_args, record.phase, nullptr));
}
}
Sample Output:
[HIP_RUNTIME_API] hipLaunchKernel
0: void const* function_address = 0x219308
1: rocprofiler_dim3_t numBlocks = {z=1, y=310, x=310}
2: rocprofiler_dim3_t dimBlocks = {z=1, y=32, x=32}
3: void** args = 0x7ffe6d8dd3c0
4: unsigned long sharedMemBytes = 0
5: ihipStream_t* stream = 0x17b40c0
[HIP_RUNTIME_API] hipMemcpyAsync
0: void* dst = 0x7f06c7bbb010
1: void const* src = 0x7f0698800000
2: unsigned long sizeBytes = 393625600
3: hipMemcpyKind kind = DeviceToHost
4: ihipStream_t* stream = 0x25dfcf0
Code Object Tracing#
The code object tracing service is a critical component for obtaining information regarding
asynchronous activity on the GPU. The rocprofiler_callback_tracing_code_object_load_data_t
payload (kind=ROCPROFILER_CALLBACK_TRACING_CODE_OBJECT, operation=ROCPROFILER_CODE_OBJECT_LOAD)
provides a unique identifier for a bundle of one or more GPU kernel symbols which have been loaded
for a specific GPU agent. For example, if your application is leveraging a multi-GPU system system
containing 4 Vega20 GPUs and 4 MI100 GPUs, there will at least 8 code objects loaded: one code
object for each GPU. Each code object will be associated with a set of kernel symbols:
the rocprofiler_callback_tracing_code_object_kernel_symbol_register_data_t payload
(kind=ROCPROFILER_CALLBACK_TRACING_CODE_OBJECT, operation=ROCPROFILER_CODE_OBJECT_DEVICE_KERNEL_SYMBOL_REGISTER)
provides a globally unique identifier for the specific kernel symbol along with the kernel name and
several other static properties of the kernel (e.g. scratch size, scalar general purpose register count, etc.).
Note: two otherwise identical kernel symbols (same kernel name, scratch size, etc.) which are part of
otherwise identical code objects but the code objects are loaded for different GPU agents will have unique
kernel identifiers. Furthermore, if the same code object (and it’s kernel symbols) are unloaded and then
re-loaded, that code object and all of it’s kernel symbols will be given new unique identifiers.
In general, when a code object is loaded and unloaded, here is the sequence of events:
Callback: code object load
kind=
ROCPROFILER_CALLBACK_TRACING_CODE_OBJECToperation=
ROCPROFILER_CODE_OBJECT_LOADphase=
ROCPROFILER_CALLBACK_PHASE_LOAD
Callback: kernel symbol load
kind=
ROCPROFILER_CALLBACK_TRACING_CODE_OBJECToperation=
ROCPROFILER_CODE_OBJECT_DEVICE_KERNEL_SYMBOL_REGISTERphase=
ROCPROFILER_CALLBACK_PHASE_LOADRepeats for each kernel symbol in code object
Application Execution
Callback: kernel symbol unload
kind=
ROCPROFILER_CALLBACK_TRACING_CODE_OBJECToperation=
ROCPROFILER_CODE_OBJECT_DEVICE_KERNEL_SYMBOL_REGISTERphase=
ROCPROFILER_CALLBACK_PHASE_UNLOADRepeats for each kernel symbol in code object
Callback: code object unload
kind=
ROCPROFILER_CALLBACK_TRACING_CODE_OBJECToperation=
ROCPROFILER_CODE_OBJECT_LOADphase=
ROCPROFILER_CALLBACK_PHASE_UNLOAD
Note: rocprofiler-sdk does not provide an interface to query this information outside of the
code object tracing service. If you wish to be able to associate kernel names with kernel tracing records,
a tool is personally responsible for making a copy of the relevant information when the code objects and
kernel symbol are loaded (however, any constant string fields like the (const char* kernel_name field)
need not to be copied, these are guaranteed to be valid pointers until after rocprofiler-sdk finalization).
If a tool decides to delete their copy of the data associated with a given code object or kernel symbol
identifier when the code object and kernel symbols are unloaded, it is highly recommended to flush
any/all buffers which might contain references to that code object or kernel symbol identifiers before
deleting the associated data.
For a sample of code object tracing, please see the samples/code_object_tracing example in the
rocprofiler-sdk GitHub repository.