hi, guys:
I modify code form axistag, to display time in x axis.
.h:

QVector<double> m_key;
    QVector<double> m_sdata;
    QVector<double> m_sdata2;

.cpp
init:

int64_t now = QTime::currentTime().msecsSinceStartOfDay();

    now -= 10*1000;
    for(int i=0;i<100;i++){
        m_key.append((now + i*100)/1000.0);
        //m_key.append(i); // ok for points display
        m_sdata.append(sin(0.6f*i));
        m_sdata2.append(cos(0.25f*i));
    }
    mGraph1->setData(m_key,m_sdata);
    mGraph2->setData(m_key,m_sdata2);
    m_cnt = 100;
    prepareDisplayData();
    mDataTimer.start(100);

in timer (100ms) to reflesh:
int64_t  nowtime = QTime::currentTime().msecsSinceStartOfDay();

    // make key axis range scroll with the data:
    ui->widCapGraphics->xAxis->rescale();
    mGraph1->rescaleValueAxis(false, true);
    mGraph2->rescaleValueAxis(false, true);

    // 改变数据
    m_key.removeFirst();
    m_key.append(nowtime/1000.0);

    m_sdata.removeFirst();
    m_sdata.append(sin(0.6f*m_cnt));

    m_sdata2.removeFirst();
    m_sdata2.append(cos(0.25f*m_cnt));

    mGraph1->setData(m_key,m_sdata,true);
    mGraph2->setData(m_key,m_sdata2,true);

the ploting seems fine:
<br /> https://img-blog.csdnimg.cn/20210213233717957.gif<br />

from task manager, i can see memory is 8060k when starting. after 7 hours, the memory increase to 10760k. why? where i should to decrease the memory used?
platform is win7+vs2017+qt5..14.1