Qt6 Windows slower than Qt6 Ubuntu

[Joe von Habsburg]

I'm working on a project. I take data with GET request and use it. When I run my code, ubuntu faster than windows, 3 times.

Qt version : 6.6.0
Ubuntu compiler : gcc
Ubuntu version : 22.04
Windows compiler : MSVS2019
Windows version : 10

Is there any way, for get same speed ubuntu and windows ?

[jsulm]

@Joe-von-Habsburg You did not post any code, so nobody knows what exactly you're doing and how

[JonB]

@Joe-von-Habsburg
And in addition to @jsulm are you able to time how long each platform takes quite outside of a Qt program.? Could easily be a platform or whatever issue.
(And btw make quite sure neither of your platform executables are compiled for debug/run under debug.)

[Joe von Habsburg]

@jsulm

This is my code for take data with get request.

void DataReceiver::start()
{
    _connection++;
    if(_connection > 1)
        return;

    qDebug() << "Starting take data";
    _takeData = true;
    while(_takeData){
        QDateTime time1 = QDateTime::currentDateTime();
        _sample = getData(54664);
        QDateTime time3 = QDateTime::currentDateTime();
        if(_takeIQData)
            _iq = getData(54665);
        QDateTime time2 = QDateTime::currentDateTime();
        qDebug() << "sample : " << time3 - time1 << " iq : " << time2 - time3 << "time : " << time2 - time1;
        emit sendData(_sample, _iq);
    }
    qDebug() << "Finished taking data";
}

QByteArray DataReceiver::getData(int port)
{
    QString url = QString("http://localhost:%1/sample").arg(port);
    QUrl apiUrl(url);
    QNetworkAccessManager manager;
    QNetworkRequest request(apiUrl);
    QNetworkReply *reply = manager.get(request);
    QEventLoop loop;
    connect(reply, &QNetworkReply::finished, &loop, &QEventLoop::quit);
    loop.exec();
    if (reply->error() == QNetworkReply::NoError) {
        QByteArray responseData = reply->readAll();
        return responseData;
        reply->deleteLater();
    } else {
        QString _error = tr("Error");
        QString _spectrum_error = tr("Spectrum error.");
        QMessageBox::critical(nullptr, _error, _spectrum_error);
        stop();
    }
    reply->deleteLater();
    return NULL;
}

[JonB]

@Joe-von-Habsburg
If you are calling this multiple times at least correct so as not to leak the QNetworkReply. Probably irrelevant, but just in case.

How do timings compare on each platform quite outside of a Qt program?

[Joe von Habsburg]

@JonB
I watch debug line and graphic. The data which is came, it's graphic data and I draw i it (drawing is 30ms).

Debug line :

qDebug() << "sample : " << time3 - time1 << " iq : " << time2 - time3 << "time : " << time2 - time1;

In ubuntu : 150ms 0ms 150ms
In windows : 400ms 0ms 400ms

How can I take data with different way ? Can you give any example?

Note: The data is come with only get request.

[JonB]

@Joe-von-Habsburg
I have suggested what you should test first, but you have said nothing each time.. I also suggested you do not test anything with the "debug" in "debug line and graphic".

[Joe von Habsburg]

@JonB I run release versions, and I saw same thing. Any advice for get request ? And is it possible, gcc more performance than msvc ?

[JonB]

@Joe-von-Habsburg
No, compiler is not going to make any difference when fetching data over a network and it's taking hundreds of milliseconds.

[Joe von Habsburg]

@JonB

I wrote basic program just taking data. (Because I suspect other code lines slow me). I saw same output.

Can you give me code example for get request ?

[JonB]

@JonB said in Qt6 Windows slower than Qt6 Ubuntu:

How do timings compare on each platform quite outside of a Qt program?

[Joe von Habsburg]

@JonB I watched graphic speed

[jsulm]

@Joe-von-Habsburg You should read more carefully what others write. What @JonB suggested is that you try to get the data with a non Qt application on both platforms to see whether the behaviour is the same or not...

[Joe von Habsburg]

@jsulm I used javascript for get request.

const deneme = async() => {
    while(true){
        var date1 = new Date();
    
        var res = await fetch('http://localhost:54664/sample')
        var data = await res.json();
        console.log("sample len : ",data.samples[0].length)
    
        var date2 = new Date();
    
        var res2 = await fetch('http://localhost:54665/sample')
        var data2 = await res2.json();
        console.log("sample len : ",data2.samples[0].length)
    
        var date3 = new Date();
    
        console.log("sample : ", date2-date1, " - iq : ", date3 - date2, " - time : ", date3 - date1);
    }
}


deneme();

I saw same times between ubuntu and windows (90ms).
I think the problem is in windows Qt. Any idea ?

[jsulm]

@Joe-von-Habsburg You should try to do your networking properly: without local event loops. Qt is asynchronous.

[Christian Ehrlicher]

... And you should/must not recreate the QNetworkAcceesManager every time.

[Joe von Habsburg]

@Christian-Ehrlicher said in Qt6 Windows slower than Qt6 Ubuntu:

And you should/must not recreate the QNetworkAcceesManager every time.

This work for me. Thank you so much :)

[Joe von Habsburg]

@Christian-Ehrlicher

I have another question. I received some times between ubuntu and windows (65ms). Everything is ok. But, sometimes windows rising 350ms for one packet. In ubuntu just max 80ms.

QByteArray DataReceiver::getData(int port)
{
    QString url = QString("http://localhost:%1/sample").arg(port);
    _apiUrl.setUrl(url);
    _request.setUrl(_apiUrl);
    _reply = _manager.get(_request);
    connect(_reply, &QNetworkReply::finished, &_loop, &QEventLoop::quit);
    _loop.exec();
    if (_reply->error() == QNetworkReply::NoError) {
        QByteArray responseData = _reply->readAll();
        _reply->deleteLater();
        return responseData;
    } else {
        QString _error = tr("Error");
        QString _spectrum_error = tr("Spectrum error.");
        QMessageBox::critical(nullptr, _error, _spectrum_error);
        stop();
    }
    _reply->deleteLater();
    return NULL;
}

Do you know, why it's rising ? What can I do another, after take data ?

[Joe von Habsburg]

@Joe-von-Habsburg I found the reason. Thanks a lot :) <3

[Volker75]

@Joe-von-Habsburg And what was the reason? Windows defender?