Add a benchmark for QSharedPointer

Initial results with GCC:

Even though GCC's assembly looks rather bad because of the implicit
fall-back from atomics to non-atomics for single-threaded
applications, libstdc++'s shared_ptr still performs twice as fast as
QSharedPointer, proving that the branch predictor eats libstdc++'s
is-multi-threaded-check for breakfast and the two atomic operations of
a QSharedPointer copy vs. one for std::shared_ptr dominate the
run-time.

********* Start testing of tst_QSharedPointer *********
Config: Using QtTest library 6.2.0, Qt 6.2.0 (x86_64-little_endian-lp64 shared (dynamic) release build; by GCC 11.1.1 20210712), ubuntu 20.04
PASS   : tst_QSharedPointer::initTestCase()
PASS   : tst_QSharedPointer::refAndDeref_null_QSP_int()
RESULT : tst_QSharedPointer::refAndDeref_null_QSP_int():
     0.0000024 msecs per iteration (total: 81, iterations: 33554432)
PASS   : tst_QSharedPointer::refAndDeref_null_SSP_int()
RESULT : tst_QSharedPointer::refAndDeref_null_SSP_int():
     0.0000024 msecs per iteration (total: 81, iterations: 33554432)
PASS   : tst_QSharedPointer::refAndDeref_null_BSP_int()
RESULT : tst_QSharedPointer::refAndDeref_null_BSP_int():
     0.0000025 msecs per iteration (total: 87, iterations: 33554432)
PASS   : tst_QSharedPointer::refAndDeref_null_QSP_QString()
RESULT : tst_QSharedPointer::refAndDeref_null_QSP_QString():
     0.0000025 msecs per iteration (total: 86, iterations: 33554432)
PASS   : tst_QSharedPointer::refAndDeref_null_SSP_QString()
RESULT : tst_QSharedPointer::refAndDeref_null_SSP_QString():
     0.0000023 msecs per iteration (total: 80, iterations: 33554432)
PASS   : tst_QSharedPointer::refAndDeref_null_BSP_QString()
RESULT : tst_QSharedPointer::refAndDeref_null_BSP_QString():
     0.0000026 msecs per iteration (total: 88, iterations: 33554432)
PASS   : tst_QSharedPointer::refAndDeref_nonnull_QSP_int()
RESULT : tst_QSharedPointer::refAndDeref_nonnull_QSP_int():
     0.000019 msecs per iteration (total: 83, iterations: 4194304)
PASS   : tst_QSharedPointer::refAndDeref_nonnull_SSP_int()
RESULT : tst_QSharedPointer::refAndDeref_nonnull_SSP_int():
     0.000010 msecs per iteration (total: 90, iterations: 8388608)
PASS   : tst_QSharedPointer::refAndDeref_nonnull_BSP_int()
RESULT : tst_QSharedPointer::refAndDeref_nonnull_BSP_int():
     0.0000094 msecs per iteration (total: 79, iterations: 8388608)
PASS   : tst_QSharedPointer::refAndDeref_nonnull_QSP_QString()
RESULT : tst_QSharedPointer::refAndDeref_nonnull_QSP_QString():
     0.000017 msecs per iteration (total: 75, iterations: 4194304)
PASS   : tst_QSharedPointer::refAndDeref_nonnull_SSP_QString()
RESULT : tst_QSharedPointer::refAndDeref_nonnull_SSP_QString():
     0.000010 msecs per iteration (total: 90, iterations: 8388608)
PASS   : tst_QSharedPointer::refAndDeref_nonnull_BSP_QString()
RESULT : tst_QSharedPointer::refAndDeref_nonnull_BSP_QString():
     0.0000091 msecs per iteration (total: 77, iterations: 8388608)
PASS   : tst_QSharedPointer::threadedRefAndDeref_null_QSP_int()
RESULT : tst_QSharedPointer::threadedRefAndDeref_null_QSP_int():
     0.000016 msecs per iteration (total: 68, iterations: 4194304)
PASS   : tst_QSharedPointer::threadedRefAndDeref_null_SSP_int()
RESULT : tst_QSharedPointer::threadedRefAndDeref_null_SSP_int():
     0.000025 msecs per iteration (total: 53, iterations: 2097152)
PASS   : tst_QSharedPointer::threadedRefAndDeref_null_BSP_int()
RESULT : tst_QSharedPointer::threadedRefAndDeref_null_BSP_int():
     0.000027 msecs per iteration (total: 58, iterations: 2097152)
PASS   : tst_QSharedPointer::threadedRefAndDeref_null_QSP_QString()
RESULT : tst_QSharedPointer::threadedRefAndDeref_null_QSP_QString():
     0.000016 msecs per iteration (total: 71, iterations: 4194304)
PASS   : tst_QSharedPointer::threadedRefAndDeref_null_SSP_QString()
RESULT : tst_QSharedPointer::threadedRefAndDeref_null_SSP_QString():
     0.000027 msecs per iteration (total: 58, iterations: 2097152)
PASS   : tst_QSharedPointer::threadedRefAndDeref_null_BSP_QString()
RESULT : tst_QSharedPointer::threadedRefAndDeref_null_BSP_QString():
     0.000017 msecs per iteration (total: 73, iterations: 4194304)
PASS   : tst_QSharedPointer::threadedRefAndDeref_nonnull_QSP_int()
RESULT : tst_QSharedPointer::threadedRefAndDeref_nonnull_QSP_int():
     0.00073 msecs per iteration (total: 96, iterations: 131072)
PASS   : tst_QSharedPointer::threadedRefAndDeref_nonnull_SSP_int()
RESULT : tst_QSharedPointer::threadedRefAndDeref_nonnull_SSP_int():
     0.000408 msecs per iteration (total: 107, iterations: 262144)
PASS   : tst_QSharedPointer::threadedRefAndDeref_nonnull_BSP_int()
RESULT : tst_QSharedPointer::threadedRefAndDeref_nonnull_BSP_int():
     0.00033 msecs per iteration (total: 89, iterations: 262144)
PASS   : tst_QSharedPointer::threadedRefAndDeref_nonnull_QSP_QString()
RESULT : tst_QSharedPointer::threadedRefAndDeref_nonnull_QSP_QString():
     0.000877 msecs per iteration (total: 115, iterations: 131072)
PASS   : tst_QSharedPointer::threadedRefAndDeref_nonnull_SSP_QString()
RESULT : tst_QSharedPointer::threadedRefAndDeref_nonnull_SSP_QString():
     0.00033 msecs per iteration (total: 89, iterations: 262144)
PASS   : tst_QSharedPointer::threadedRefAndDeref_nonnull_BSP_QString()
RESULT : tst_QSharedPointer::threadedRefAndDeref_nonnull_BSP_QString():
     0.000385 msecs per iteration (total: 101, iterations: 262144)
PASS   : tst_QSharedPointer::cleanupTestCase()
Totals: 26 passed, 0 failed, 0 skipped, 0 blacklisted, 7995ms
********* Finished testing of tst_QSharedPointer *********

Change-Id: I0bed70142ffdbde6898ec0e27cb470b50fc0e97d
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
This commit is contained in:
Marc Mutz 2021-07-12 17:50:04 +02:00
parent df62fdb51c
commit 18113e22e9
3 changed files with 133 additions and 0 deletions

View File

@ -8,5 +8,6 @@ add_subdirectory(qlist)
add_subdirectory(qmap)
add_subdirectory(qrect)
add_subdirectory(qringbuffer)
add_subdirectory(qsharedpointer)
add_subdirectory(qstack)
add_subdirectory(qvector)

View File

@ -0,0 +1,9 @@
qt_internal_add_benchmark(tst_bench_shared_ptr
SOURCES
tst_bench_shared_ptr.cpp
INCLUDE_DIRECTORIES
.
PUBLIC_LIBRARIES
Qt::Core
Qt::Test
)

View File

@ -0,0 +1,123 @@
/****************************************************************************
**
** Copyright (C) 2021 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz <marc.mutz@kdab.com>
** Contact: https://www.qt.io/licensing/
**
** This file is part of the test suite of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:GPL-EXCEPT$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3 as published by the Free Software
** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include <QObject>
#include <QScopeGuard>
#include <QSharedPointer>
#include <QTest>
#include <atomic>
#include <memory>
#include <thread>
#include <vector>
#if __has_include(<boost/shared_ptr.hpp>)
# include <boost/shared_ptr.hpp>
# include <boost/make_shared.hpp>
# define ONLY_IF_BOOST(x) x
#else
# define ONLY_IF_BOOST(x) QSKIP("This benchmark requires Boost.SharedPtr.")
#endif
class tst_QSharedPointer : public QObject
{
Q_OBJECT
private Q_SLOTS:
void refAndDeref_null_QSP_int() { refAndDeref<QSharedPointer<int>>(); }
void refAndDeref_null_SSP_int() { refAndDeref<std::shared_ptr<int>>(); }
void refAndDeref_null_BSP_int() { ONLY_IF_BOOST(refAndDeref<boost::shared_ptr<int>>()); }
void refAndDeref_null_QSP_QString() { refAndDeref<QSharedPointer<QString>>(); }
void refAndDeref_null_SSP_QString() { refAndDeref<std::shared_ptr<QString>>(); }
void refAndDeref_null_BSP_QString() { ONLY_IF_BOOST(refAndDeref<boost::shared_ptr<QString>>()); }
void refAndDeref_nonnull_QSP_int() { refAndDeref(QSharedPointer<int>::create(42)); }
void refAndDeref_nonnull_SSP_int() { refAndDeref(std::make_shared<int>(42)); }
void refAndDeref_nonnull_BSP_int() { ONLY_IF_BOOST(refAndDeref(boost::make_shared<int>(42))); }
void refAndDeref_nonnull_QSP_QString() { refAndDeref(QSharedPointer<QString>::create(QStringLiteral("Hello"))); }
void refAndDeref_nonnull_SSP_QString() { refAndDeref(std::make_shared<QString>(QStringLiteral("Hello"))); }
void refAndDeref_nonnull_BSP_QString() { ONLY_IF_BOOST(refAndDeref(boost::make_shared<QString>(QStringLiteral("Hello")))); }
private:
template <typename SP>
void refAndDeref(SP sp = {})
{
QBENCHMARK {
[[maybe_unused]] auto copy = sp;
}
}
private Q_SLOTS:
void threadedRefAndDeref_null_QSP_int() { threadedRefAndDeref<QSharedPointer<int>>(); }
void threadedRefAndDeref_null_SSP_int() { threadedRefAndDeref<std::shared_ptr<int>>(); }
void threadedRefAndDeref_null_BSP_int() { ONLY_IF_BOOST(threadedRefAndDeref<boost::shared_ptr<int>>()); }
void threadedRefAndDeref_null_QSP_QString() { threadedRefAndDeref<QSharedPointer<QString>>(); }
void threadedRefAndDeref_null_SSP_QString() { threadedRefAndDeref<std::shared_ptr<QString>>(); }
void threadedRefAndDeref_null_BSP_QString() { ONLY_IF_BOOST(threadedRefAndDeref<boost::shared_ptr<QString>>()); }
void threadedRefAndDeref_nonnull_QSP_int() { threadedRefAndDeref(QSharedPointer<int>::create(42)); }
void threadedRefAndDeref_nonnull_SSP_int() { threadedRefAndDeref(std::make_shared<int>(42)); }
void threadedRefAndDeref_nonnull_BSP_int() { ONLY_IF_BOOST(threadedRefAndDeref(boost::make_shared<int>(42))); }
void threadedRefAndDeref_nonnull_QSP_QString() { threadedRefAndDeref(QSharedPointer<QString>::create(QStringLiteral("Hello"))); }
void threadedRefAndDeref_nonnull_SSP_QString() { threadedRefAndDeref(std::make_shared<QString>(QStringLiteral("Hello"))); }
void threadedRefAndDeref_nonnull_BSP_QString() { ONLY_IF_BOOST(threadedRefAndDeref(boost::make_shared<QString>(QStringLiteral("Hello")))); }
private:
template <typename SP>
void threadedRefAndDeref(SP sp = {})
{
std::atomic<bool> cancel = false;
std::vector<std::thread> threads;
const auto numCores = std::max(2U, std::thread::hardware_concurrency());
for (uint i = 0; i < numCores - 1; ++i) {
threads.emplace_back([sp, &cancel] {
while (!cancel.load(std::memory_order_relaxed)) {
for (int i = 0; i < 100; ++i)
[[maybe_unused]] auto copy = sp;
}
});
}
const auto join = qScopeGuard([&] {
cancel.store(true, std::memory_order_relaxed);
for (auto &t : threads)
t.join();
});
QBENCHMARK {
[[maybe_unused]] auto copy = sp;
}
}
};
QTEST_MAIN(tst_QSharedPointer)
#include "tst_bench_shared_ptr.moc"