I'm looking at optimizing an applications save performance - it is too slow right now and causes too much of a freeze. We're using QXmlStreamWriter, here's the implementation <https://github.com/Mudlet/Mudlet/blob/development/src/XMLexport.cpp>.
Profiling suggests that Qt's write element / attribute method is too slow ( screenshot <https://imgur.com/a/UUVSp4I>, results attached). Is there anything I can do it speed it up? I tried giving it a QBuffer instead of a QFile, but the difference was marginal. A lot of time seems to be spent resizing the buffer, and unfortunately there doesn't seem to be a way to pre-set the QBuffer size to something reasonable to begin with. Anyone have tips?
"Function / Call Stack","CPU Time","Module","Function (Full)","Source File","Start Address" "QIODevice::write","0.0399935","libQt5Core.so.5","QIODevice::write(char const*, long long)","[Unknown]","0x1ad360" " func@0x310fe0","0.0399935","libQt5Core.so.5","func@0x310fe0","[Unknown]","0x310fe0" " func@0x3111b0 <- func@0x312d60 <- QXmlStreamWriter::writeStartElement <- QXmlStreamWriter::writeTextElement <- XMLexport::writeTrigger <- XMLexport::writeTrigger <- XMLexport::writeTrigger <- XMLexport::writeTrigger <- XMLexport::writeHost <- XMLexport::exportHost <- Host::saveProfile <- TLuaInterpreter::saveProfile <- lua_pcall <- TLuaInterpreter::call <- TAlias::execute <- TAlias::match <- AliasUnit::processDataStream <- Host::send <- TCommandLine::enterCommand <- TCommandLine::event <- QApplicationPrivate::notify_helper <- QApplication::notify <- QCoreApplication::notifyInternal2 <- func@0x1b22b0 <- QApplicationPrivate::notify_helper <- QApplication::notify <- QCoreApplication::notifyInternal2 <- QGuiApplicationPrivate::processKeyEvent <- QGuiApplicationPrivate::processWindowSystemEvent <- QWindowSystemInterface::sendWindowSystemEvents <- func@0xd8b70 <- QEventLoop::exec <- QCoreApplication::exec <- main <- __libc_start_main <- _start","0.0199958","libQt5Core.so.5","func@0x3111b0","[Unknown]","0x3111b0" " QXmlStreamWriter::writeAttribute <- XMLexport::writeAction <- XMLexport::writeAction <- XMLexport::writeAction <- XMLexport::writeHost <- XMLexport::exportHost <- Host::saveProfile <- TLuaInterpreter::saveProfile <- lua_pcall <- TLuaInterpreter::call <- TAlias::execute <- TAlias::match <- AliasUnit::processDataStream <- Host::send <- TCommandLine::enterCommand <- TCommandLine::event <- QApplicationPrivate::notify_helper <- QApplication::notify <- QCoreApplication::notifyInternal2 <- func@0x1b22b0 <- QApplicationPrivate::notify_helper <- QApplication::notify <- QCoreApplication::notifyInternal2 <- QGuiApplicationPrivate::processKeyEvent <- QGuiApplicationPrivate::processWindowSystemEvent <- QWindowSystemInterface::sendWindowSystemEvents <- func@0xd8b70 <- QEventLoop::exec <- QCoreApplication::exec <- main <- __libc_start_main <- _start","0.011999","libQt5Core.so.5","QXmlStreamWriter::writeAttribute(QString const&, QString const&)","[Unknown]","0x3115e0" " func@0x312d60 <- QXmlStreamWriter::writeStartElement <- QXmlStreamWriter::writeTextElement <- XMLexport::writeTrigger <- XMLexport::writeTrigger <- XMLexport::writeTrigger <- XMLexport::writeHost <- XMLexport::exportHost <- Host::saveProfile <- TLuaInterpreter::saveProfile <- lua_pcall <- TLuaInterpreter::call <- TAlias::execute <- TAlias::match <- AliasUnit::processDataStream <- Host::send <- TCommandLine::enterCommand <- TCommandLine::event <- QApplicationPrivate::notify_helper <- QApplication::notify <- QCoreApplication::notifyInternal2 <- func@0x1b22b0 <- QApplicationPrivate::notify_helper <- QApplication::notify <- QCoreApplication::notifyInternal2 <- QGuiApplicationPrivate::processKeyEvent <- QGuiApplicationPrivate::processWindowSystemEvent <- QWindowSystemInterface::sendWindowSystemEvents <- func@0xd8b70 <- QEventLoop::exec <- QCoreApplication::exec <- main <- __libc_start_main <- _start","0.0079987","libQt5Core.so.5","func@0x312d60","[Unknown]","0x312d60" "QBuffer::writeData","0.036005","libQt5Core.so.5","QBuffer::writeData(char const*, long long)","[Unknown]","0x18f650" "QByteArray::resize","0.0279967","libQt5Core.so.5","QByteArray::resize(int)","[Unknown]","0xb02e0" "__GI_","0.0200273","libc.so.6","long double __GI_(long, int, bool, char)","malloc.c","0x8fa00" "__GI_","0.0160065","libc.so.6","float __GI_(long, int, bool, char)","malloc.c","0x8f3e0" "__GI___libc_malloc","0.0120044","libc.so.6","__GI___libc_malloc","malloc.c","0x8eeb0" "QByteArray::QByteArray","0.0120013","libQt5Core.so.5","QByteArray::QByteArray(int, Qt::Initialization)","[Unknown]","0xb0050" "qCalculateGrowingBlockSize","0.0119998","libQt5Core.so.5","qCalculateGrowingBlockSize(unsigned long, unsigned long, unsigned long)","[Unknown]","0xaf6b0" "operator==","0.0119998","libQt5Core.so.5","operator==(QString const&, QStringRef const&)","[Unknown]","0x12cbf0" "xcb_wait_for_event","0.01","libxcb.so.1","xcb_wait_for_event","[Unknown]","0xd4f0" "__memcpy_sse2_unaligned_erms","0.01","libc.so.6","__memcpy_sse2_unaligned_erms","memmove-vec-unaligned-erms.S","0xb2350" "QMutex::lock","0.01","libQt5Core.so.5","QMutex::lock(void)","[Unknown]","0xa3930" "XMLexport::writeTrigger","0.00800122","mudlet","XMLexport::writeTrigger(TTrigger*)","XMLexport.cpp","0x3c81e0" "func@0x310cd0","0.00800097","libQt5Core.so.5","func@0x310cd0","[Unknown]","0x310cd0" "__GI___strlen_sse2","0.00800066","libc.so.6","__GI___strlen_sse2","strlen.S","0xa8450" "QArrayData::allocate","0.00799505","libQt5Core.so.5","QArrayData::allocate(unsigned long, unsigned long, unsigned long, QFlags<QArrayData::AllocationOption>)","[Unknown]","0xad750" "func@0x2da260","0.00799491","libQt5Core.so.5","func@0x2da260","[Unknown]","0x2da260" "QString::resize","0.00797939","libQt5Core.so.5","QString::resize(int)","[Unknown]","0x120780" "FT_Matrix_Multiply","0.00399347","libfreetype.so.6","FT_Matrix_Multiply","[Unknown]","0xd690"
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