[loup-vaillant]

I'm writing a little C++/Qt application to visualise a fairly small amount of data.

The lag is already noticeable. If I don't pay attention to performance, I know the end result will be slow and unpleasant to use.

[afiori]

That is true, but you are likely better off using a library than focusing yourself on cache optimization.

[loup-vaillant]

Using a library (specifically, taking advantage of Qt's QVariant and view/model framework), is what triggered most of the slowdown.