Qt6 Windows slower than Qt6 Ubuntu

[jsulm]

@Joe-von-Habsburg said in Qt6 Windows slower than Qt6 Ubuntu:

You suggested to me "readyRead" signal but now, I could not readyAll because, incomplated data is received

As already suggested: you need to accumulate incoming data in a buffer. readyRead() signal can be emited several times until you get everything.

"Do you mean say "finished" signal ?" - yes
https://doc.qt.io/qt-6/qnetworkreply.html#finished
It even explains: "In particular, if no calls to read() were made as a result of readyRead(), a call to readAll() will retrieve the full contents in a QByteArray."

[Joe von Habsburg]

@jsulm said in Qt6 Windows slower than Qt6 Ubuntu:

As already suggested: you need to accumulate incoming data in a buffer. readyRead() signal can be emited several times until you get everything.

Hmm now I should not assign reply->readAll(), I should append :). I will try it.

_sample.append(_replySample->readAll());

@jsulm said in Qt6 Windows slower than Qt6 Ubuntu:

"Do you mean say "finished" signal ?" - yes

I cannot use it because memory leak.

[JonB]

@Joe-von-Habsburg
As @jsulm has said. With QNetworkAccessManager::setAutoDeleteReplies(true) set you should be able to use either of the following approaches:

QByteArray _bytesRead;    // class member variable

_bytesRead.clear();
connect(_reply, &QNetworkReply::finished, this, &Class::onFinished);
_reply = _manager.get(_request);

void Class::onFinished()
{
    _bytesRead = _reply->readAll();    // read all bytes in one go at the end, just before `_reply` gets auto-deleted
}

or

QByteArray _bytesRead;    // class member variable

_bytesRead.clear();
connect(_reply, &QNetworkReply::readyRead, this, &Class::onReadyRead);
connect(_reply, &QNetworkReply::finished, this, &Class::onFinished);
_reply = _manager.get(_request);

void Class::onReadyRead()
{
    _bytesRead += _reply->readAll();    // *append* this time's bytes read to buffer
}

void Class::onFinished()
{
    // I think `_bytesRead` should contain all data by now, when reply has finished
    // If not call `_bytesRead += _reply->readAll();` or `onReadyRead()` one last time
}

[Edit: Fixed code highlighting ~kshegunov]

[jsulm]

@Joe-von-Habsburg said in Qt6 Windows slower than Qt6 Ubuntu:

cannot use it because memory leak.

There should not be memory leak unless your code is wrong.
Simply connect a slot to finished() signal and in that slot call readAll() and deleteLater() on the reply.

[Joe von Habsburg]

@JonB said in Qt6 Windows slower than Qt6 Ubuntu:

QByteArray _bytesRead; // class member variable

_bytesRead.clear();
connect(_reply, &QNetworkReply::readyRead, this, &Class::onReadyRead);
connect(_reply, &QNetworkReply::finished, this, &Class::onFinished);
_reply = _manager.get(_request);

void Class::onReadyRead()
{
_bytesRead += _reply->readAll(); // append this time's bytes read to buffer
}

void Class::onFinished()
{
// I think _bytesRead should contain all data by now, when reply has finished
// If not call _bytesRead += _reply->readAll(); or onReadyRead() one last time
}

its work !!! Thank you so much

[JonB]

@Joe-von-Habsburg
Do your timings/memory consumption with this asynchronous approach (i.e. no _loop.exec()) and not with that original while() loop. (If you want to run it more than once, after you get finished() on one start the next one there or on a QTimer::singleShot().) See whether you still get bad performance on one versus the other.

[Joe von Habsburg]

@JonB

Last edit my code :

DataReceiver::DataReceiver(QObject *parent)
   : QObject{parent}
{
   _manager.setAutoDeleteReplies(true);
}
void DataReceiver::start()
{
   _connection++;
   if(_connection > 1)
       return;

   _takeData = true;
   run();
}

void DataReceiver::stop()
{
   _takeData = false;
   _connection = 0;
   _data.clear();
}


void DataReceiver::getData()
{
   _data.clear();
   QString url = QString("http://localhost:%1/sample").arg(_port);
   QUrl _apiUrl(url);
   QNetworkRequest _request(_apiUrl);
   _reply = _manager.get(_request);
   connect(_reply, &QNetworkReply::readyRead, this, &DataReceiver::onReadReady);
   connect(_reply, &QNetworkReply::finished, this, &DataReceiver::onFinished);
}


void DataReceiver::run()
{
   if(!_takeData)
       return;

   getData();
}

void DataReceiver::onReadReady()
{
   _data += _reply->readAll();
}

void DataReceiver::onFinished()
{
   emit sendData(_data);
   run();
}

its working. time slow down from 65ms to 165ms but its working.