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Introduction to Intel® Graphics Performance Analyzers
Game Optimization Methodology
Install and Launch Intel® GPA
Launch Application for Analysis
Configure Analysis Settings
Analyze Desktop Graphics Applications
Quick Start with Profiling Unreal Engine* Games
Instrumentation and Tracing Technology API Support
Intel® GPA Reference
Notices and Disclaimers
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Task API
A task is a logical unit of work performed by a particular thread. Tasks can nest; thus, tasks typically correspond to functions, scopes, or a case block in a switch statement. You can use the Task API to assign tasks to threads.
The Task API does not enable a thread to suspend the current task and switch to a different task (task switching), or move a task to a different thread (task stealing).
A task instance represents a piece of work performed by a particular thread for a period of time. The task is defined by the bracketing of __itt_task_begin() and __itt_task_end() on the same thread.
Tasks can be of two types: simple or overlapped.
Simple tasks implicitly support a concept of embedded execution. This means that the call __itt_task_end() finalizes the most recent __itt_task_begin() call. For example, the following metacode is a valid sequence, and execution time of “a” tasks incorporates the execution time of “b” tasks:
__itt_task_begin(a)
__itt_task_begin(b)
__itt_task_end(b)
__itt_task_end(a)
Execution regions of overlapped tasks may intercept. For example, the following metacode is a valid sequence, and a “b” task started after an “a” task can finish upon completion of the “a” task:
__itt_task_begin_overlapped(a)
__itt_task_begin_overlapped(b)
__itt_task_end_overlapped(a)
__itt_task_end_overlapped(b)
Task API Functions
To create a simple task instance on a thread, use the following functions:
void ITTAPI __itt_task_begin (const __itt_domain *domain,__itt_id taskid, __itt_id parentid, __itt_string_handle *name)
void ITTAPI __itt_task_begin_fn (const __itt_domain *domain,__itt_id taskid, __itt_id parentid, void* address)
void ITTAPI __itt_task_end (const __itt_domain *domain)
To create a simple task instance in a different clock domain, use the following functions:
void ITTAPI __itt_task_begin_ex(const __itt_domain* domain, __itt_clock_domain* clock_domain, unsigned long long timestamp, __itt_id taskid, __itt_id parentid, __itt_string_handle* name)
void ITTAPI __itt_task_begin_fn_ex(const __itt_domain* domain, __itt_clock_domain* clock_domain, unsigned long long timestamp, __itt_id taskid, __itt_id parentid, void* fn)
void ITTAPI _itt_task_end_ex(const __itt_domain* domain, __itt_clock_domain* clock_domain, unsigned long long timestamp)
To create an overlapped task instance on a thread, use the following functions:
void ITTAPI __itt_task_begin_overlapped(const __itt_domain* domain, __itt_id taskid, __itt_id parentid, __itt_string_handle* name)
void ITTAPI __itt_task_end_overlapped(const __itt_domain *domain, __itt_id taskid)
The argument taskid is mandatory for these functions.
To create an overlapped task instance in a different clock domain, use the following functions:
void ITTAPI __itt_task_begin_overlapped_ex(const __itt_domain* domain, __itt_clock_domain* clock_domain, unsigned long long timestamp, __itt_id taskid, __itt_id parentid, __itt_string_handle* name)
void ITTAPI __itt_task_end_overlapped_ex(const __itt_domain* domain, __itt_clock_domain* clock_domain, unsigned long long timestamp, __itt_id taskid)
The argument taskid is mandatory for these functions.
ITTAPI__itt_task_* Function Parameters
The following table defines the parameters used in the Task API primitives.
Type |
Parameter |
Description |
|---|---|---|
[in] |
__itt_domain |
The domain of the task. |
[in] |
__itt_id taskid |
User-defined ID optional for all task instances, except for overlapped task instances. __itt_null can be used as default for undefined task instances. Task ID is used to define relations between task instances. |
[in] |
__itt_id parentid |
Optional parameter. Parent instance ID, to which the task belongs, or __itt_null. |
[in] |
__itt_string_handle |
The task string handle. |
[in] |
void* fn |
Function address that can be used instead of the name. For example, the function address can be resolved into the function name by using debug symbol information. |
[in] |
__itt_clock_domain |
User-defined clock domain. |
[in] |
unsigned long long timestamp |
User-defined timestamp for the corresponding clock domain. |
Usage Example
The following code snippet creates a domain and a couple of tasks at global scope.
#include "ittnotify.h"
void do_foo(double seconds);
__itt_domain* domain = __itt_domain_create(__TEXT("MyTraces.MyDomain"));
__itt_string_handle* shMyTask = __itt_string_handle_create(__TEXT("My Task");
__itt_string_handle* shMySubtask = __itt_string_handle_create(__TEXT("My SubTask"));
void BeginFrame() {
__itt_task_begin(domain, __itt_null, __itt_null, shMyTask);
do_foo(1);
}
void DoWork() {
__itt_task_begin(domain, __itt_null, __itt_null, shMySubtask);
do_foo(1);
__itt_task_end(domain);
}
void EndFrame() {
do_foo(1);
__itt_task_end(domain);
}
int main() {
BeginFrame();
DoWork();
EndFrame();
return 0;
}