Qt6 Windows slower than Qt6 Ubuntu
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@JonB said in Qt6 Windows slower than Qt6 Ubuntu:
setAutoDeleteReplies(true)
this is crashed my program when I do something.
if I do it :
_manager.setAutoDeleteReplies(true);
memory and speed ok, but program crashed anytime , when I do anything. because reply deleted. why ?
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@Joe-von-Habsburg
I would guess you need to not delete it yourself now (_reply->deleteLater()
) since it is being auto-deleted onQNetworkReply::finished
?However if it is being auto-deleted on
finished
then, because you do_loop.exec();
which waits forfinished
I would guess you can no longer do_reply->readAll()
after the loop, that sounds like crash. You could instead do your data reading inside the loop instead of afterwards.I really don't know, and have never used any of this stuff :) It was suggestions for narrowing down where the "leakage" might be. But you need someone else if you need someone who truly knows about it.
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@JonB said in Qt6 Windows slower than Qt6 Ubuntu:
You could instead do your data reading inside the loop instead of afterwards.
can you give me code example ?
@JonB said in Qt6 Windows slower than Qt6 Ubuntu:
But you need someone else if you need someone who truly knows about it.
Yes but who will be :D
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@Joe-von-Habsburg said in Qt6 Windows slower than Qt6 Ubuntu:
can you give me code example ?
loop.exec()
is just a convenience, which blocks tillfinished()
, making your call "synchronous". Instead you can deal with all the data which arrives when it arrives (instead of afterfinished()
) by attaching a slot to_reply->readyRead()
signal.Of course, if you remove
_loop.exec()
fromgetData()
it will exit while network stuff is still going on, you must not have local variables which go out of scope. You will have to do quite a bit of code reorganizing. And it might be to no avail, I don't know what it will reveal or whether it will solve anything. -
@JonB said in Qt6 Windows slower than Qt6 Ubuntu:
loop.exec() is just a convenience, which blocks till finished(), making your call "synchronous". Instead you can deal with all the data which arrives when it arrives (instead of after finished()) by attaching a slot to _reply->readyRead() signal.
I changed my code.
void DataReceiver::start() { if(!_takeData) return; QDateTime time1 = QDateTime::currentDateTime(); getDataSample(); //_sample = getData(54664); QDateTime time3 = QDateTime::currentDateTime(); if(_takeIQData) getDataIQ(); //_iq = getData(54665); QDateTime time2 = QDateTime::currentDateTime(); qDebug() << "sample : " << time3 - time1 << " iq : " << time2 - time3 << "time : " << time2 - time1; } void DataReceiver::getDataSample() { QString url = QString("http://localhost:%1/sample").arg(54664); QUrl _apiUrl(url); QNetworkRequest _request(_apiUrl); _replySample = _managerSample.get(_request); connect(_replySample, &QNetworkReply::readyRead, this, &DataReceiver::readSample); } void DataReceiver::getDataIQ() { QString url = QString("http://localhost:%1/sample").arg(54665); QUrl _apiUrl(url); QNetworkRequest _request(_apiUrl); _replyIQ = _managerIQ.get(_request); connect(_replyIQ, &QNetworkReply::readyRead, this, &DataReceiver::readIQ); } void DataReceiver::readSample() { _sample = _replySample->readAll(); _replySample->deleteLater(); if(!_takeIQData){ emit sendData(_sample, _iq); _sample.clear(); _iq.clear(); start(); } } void DataReceiver::readIQ() { _iq = _replyIQ->readAll(); _replyIQ->deleteLater(); if(_takeIQData){ emit sendData(_sample, _iq); _sample.clear(); _iq.clear(); start(); } }
After a while crashing :(
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@Joe-von-Habsburg said in Qt6 Windows slower than Qt6 Ubuntu:
After a while crashing :(
I found the reason. Because readReady() sometimes receives incomplete data.
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@Joe-von-Habsburg said in Qt6 Windows slower than Qt6 Ubuntu:
sometimes receives incomplete data
Yes, because there is no guarantee that you get all data in one piece. That's why you need to buffer incoming data until you received a whole package of data.
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@jsulm... or use the requestFinished signal 🙂
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@jsulm said in Qt6 Windows slower than Qt6 Ubuntu:
Yes, because there is no guarantee that you get all data in one piece. That's why you need to buffer incoming data until you received a whole package of data.
Yes, I try downloadProgress signal like that:
void DataReceiver::downloadProgressSample(qint64 bytesReceived, qint64 bytesTotal) { if(bytesReceived == bytesTotal){ _isSampleOk = true; _sampleLen = bytesReceived; } else{ _isSampleOk = false; _sampleLen = 0; } }
but so many times, my QByteArray's length and bytesReceived are not equal.... and my program slowing for that.
@Christian-Ehrlicher said in Qt6 Windows slower than Qt6 Ubuntu:
or use the requestFinished signal
I could not see requestFinished signal on documentation. Do you mean say finished signal ?
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@Joe-von-Habsburg
Exactly as my colleagues have replied above forreadyRead()
.If you are still pursuing the difference in memory usage you report. A couple of points about your code:
You have a couple of calls to
getData()
inside some loop,while (_takeData)
. YourgetData()
uses (or used to use, you may have changed that now)_reply->deleteLater()
. Although you have aQEventLoop::exec()
call, which will allow signals/slots to flow, this is not the top-level Qt event loop. I believedeleteLater()
causes deferred deletes, meaning that the memory is not actually released until the top-level event loop is re-entered. You should not use awhile
loop like this for your tests: allow the top-level Qt event loop to be re-entered.getData()
returns aQByteArray
. We do not know what your code does with that result: for all we know you retain that somewhere, and that would eat up memory.To investigate properly you should produce a minimal reproducible example with "good" code, to be sure what you are looking at.
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@Joe-von-Habsburg said in Qt6 Windows slower than Qt6 Ubuntu:
Yes, I try downloadProgress signal like that
What does this have to do with buffering incoming data?
To get a simpler solution follow @Christian-Ehrlicher suggestion. -
@Joe-von-Habsburg said in Qt6 Windows slower than Qt6 Ubuntu:
but so many times, my QByteArray's length and bytesReceived are not equal.... and my program slowing for that.
I don't understand your point or question here? If you
readyRead()
as you go along or useQNetworkReply::downloadProgress()
you will (almost certainly) see data arrive in "chunks", i.e. multiple calls until all the data is received. That is how the data is being transmitted, and is quite normal/expected.As I wrote earlier, if you do not want to handle partial data as it arrives, and are using reply auto-delete so you cannot access it after it has finished, you can place a slot on
QNetworkReply::finished
andreadAll()
the data there in one go, before allowing the reply to be deleted. -
@jsulm said in Qt6 Windows slower than Qt6 Ubuntu:
What does this have to do with buffering incoming data?
To get a simpler solution follow @Christian-Ehrlicher suggestion.I could not see requestFinished signal on documentation. Do you mean say "finished" signal ?
@JonB said in Qt6 Windows slower than Qt6 Ubuntu:
don't understand your point or question here?
My question is that. if I use "finished" signal memory leak.
@JonB said in Qt6 Windows slower than Qt6 Ubuntu:
_reply->readyRead()
You suggested to me "readyRead" signal but now, I could not readyAll because, incomplated data is received.
For example, data's size must be 350000, but i receive 348000 or less. As a result of for that I crashed.
@JonB said in Qt6 Windows slower than Qt6 Ubuntu:
QNetworkReply::downloadProgress()
I try check will have arrived data size use with "downloadProgress" signal and my QByteArray data size is equal ? but so many times thay are not.
How can I wait all data complate without use "finished" signal because memory leak?
@JonB said in Qt6 Windows slower than Qt6 Ubuntu:
As I wrote earlier, if you do not want to handle partial data as it arrives, and are using reply auto-delete so you cannot access it after it has finished, you can place a slot on QNetworkReply::finished and readAll() the data there in one go, before allowing the reply to be deleted.
I don't understand. Can you give me code example ?
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@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." -
@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.
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@Joe-von-Habsburg
As @jsulm has said. WithQNetworkAccessManager::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]
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@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. -
@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();
oronReadyRead()
one last time
}its work !!! Thank you so much
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@Joe-von-Habsburg
Do your timings/memory consumption with this asynchronous approach (i.e. no_loop.exec()
) and not with that originalwhile()
loop. (If you want to run it more than once, after you getfinished()
on one start the next one there or on aQTimer::singleShot()
.) See whether you still get bad performance on one versus the other. -
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.