About multithreaded call CopyFileEx copy large files (more than 1GB) when the phenomenon of suspended animation

[lwei2]

@jsulm I didn't say that the child thread cannot run on the main thread.What I want to say is that the main thread is stalled because the child thread is waiting for the return value of CopyFileEx without running the code behind CopyFileEx.Such as:

void run()
{
    const wchar_t *src = reinterpret_cast<const wchar_t *>(srcPath.utf16());
    const wchar_t *dst = reinterpret_cast<const wchar_t *>(dstPath.utf16());
    m_nCopyValue = 0;
    emit sigCopyValue(0, m_nCopyValue);
    qWarning()<<"m_nCopyValue="<<m_nCopyValue;
    BOOL m_bCancel = FALSE;
    qWarning()<<"startTime="<<QTime::currentTime().toString("hh:mm:ss");
    CopyFileEx((LPCWSTR)src,(LPCWSTR)dst, CallBackCopyProgressFunc, this, (LPBOOL)m_bCancel, COPY_FILE_FAIL_IF_EXISTS);  //wait 30 to 60 seconds before executing the following code

//there is other code here

}

[JonB]

@lwei2 said in About multithreaded call CopyFileEx copy large files (more than 1GB) when the phenomenon of suspended animation:

the main thread is stalled because the child thread is waiting for the return value of CopyFileEx

Your main thread cannot afford to wait on the child thread! If the child runs CopyFileEx it's going not going to exit until that has had its extra 30 seconds at the end, which is the whole point of what you are wanting to avoid.

That's why if it waits at all the main thread should only wait until the child signals the 100% completion.

If you are using the wait on the child thread for some other purpose, then you will need a third thread for the CopyFileEx. Whatever, the only way you will be able to avoid waiting for the CopyFileEx's extra 30 seconds is if the CopyFileEx runs in its own thread, and sends a signal when the 100% is reached.

[JoeCFD]

@lwei2 It is flushing time. Therefore, progress display is sort of a lie. But on Windows you may try some MS code for file copy and do not use Qt file copy. I recently coded file copy on Linux with Qt and can not do anything about flushing.
If the file size is too big, chop the file into small pieces and copy them one after another since you may need cancel feature. The optimal size is 131072.

[lwei2]

@JonB Could you please tell me how I can wait for it to copy to 100% before sending the signal?

[SGaist]

Hi,

Did you consider using the COPY_FILE_NO_BUFFERING flag as recommended in the documentation for large files ?

[JonB]

@lwei2 said in About multithreaded call CopyFileEx copy large files (more than 1GB) when the phenomenon of suspended animation:

@JonB Could you please tell me how I can wait for it to copy to 100% before sending the signal?

I really don't understand. You said that presently CopyFileEx does not return till after the extra 30 seconds of "flushing" at the end, so if that is what you mean don't send the signal till CopyFileEx is done, which is what you have now. If you mean when the progress reaches 100%, before the extra 30 seconds, then you detect that in your CallBackCopyProgressFunc, and send the signal from there. This latter approach will require the CopyFileEx be run in its own thread.

In any case, first try @SGaist excellent spot of COPY_FILE_NO_BUFFERING flag, it might change the behaviour over to what you want by eliminating a large "flush" at the end.

[lwei2]

@SGaist I tried to use COPY_FILE_NO_BUFFERING, but I had the same problem.