Add QObject allocation benchmarks

The benchmark measures the performance of QObject allocation,
including costs of memory allocations.

Change-Id: I5d8ecfb97fe0be3375340b5ce84eb423e8a4ddaf
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
This commit is contained in:
Jędrzej Nowacki 2019-02-26 09:31:18 +01:00 committed by Volker Hilsheimer
parent ce8ab39a08
commit 949482f8e4

View File

@ -51,8 +51,55 @@ private slots:
void connect_disconnect_benchmark_data();
void connect_disconnect_benchmark();
void receiver_destroyed_benchmark();
void stdAllocator();
};
class QObjectUsingStandardAllocator : public QObject
{
Q_OBJECT
public:
QObjectUsingStandardAllocator()
{
}
};
template<class T>
inline void allocator()
{
// We need to allocate certain amount of objects otherwise the new implementation
// may re-use the previous allocation, hiding the somehow high cost of allocation. It
// also helps us to reduce the noise ratio, which is high for memory allocation.
//
// The check depends on memory allocation performance, which is quite non-deterministic.
// When a new memory is requested, the new operator, depending on implementation, is trying
// to re-use existing, already allocated for the process memory. If there is not enough, it
// asks OS to give more. Of course the first case is faster then the second. In the same
// time, from an application perspective the first is also more likely.
//
// As a result, depending on which use-case one wants to test, it may be recommended to run this
// test in separation from others, to "force" expensive code path in the memory allocation.
//
// The time based results are heavily affected by background noise. One really needs to
// prepare OS (no other tasks, CPU and RAM reservations) to run this test, or use
// instruction counting which seems to be less fragile.
const int count = 256 * 1024;
QScopedPointer<T> objects[count];
QBENCHMARK_ONCE {
for (int i = 0; i < count; ++i)
objects[i].reset(new T);
for (int i = 0; i < count; ++i)
objects[i].reset();
}
}
void QObjectBenchmark::stdAllocator()
{
allocator<QObjectUsingStandardAllocator>();
}
struct Functor {
void operator()(){}
};