300KB of RAM lost after New and Delete

[masterbraind]

After a New and a delete of a QDialog I lost 300KB of RAM. The problem become worst while more dialogs I use.

I check the memory consumption starting my app in background and calling the command "free". At the begining after create and show the dialog the empty dialog consumes 1MB, after delete this object it leaves 300KB occupied.
How can I release that memory?

TErrorDialog  *PantallaError;
PantallaError = new TErrorDialog /*Form*/;
PantallaError->show();

TErrorDialog  *PantallaError;
PantallaError = new TErrorDialog /*Form*/;
PantallaError->show();

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Here it consumes 1MB, checked with comand "free"

PantallaError->hide();
      PantallaError->deleteLater(); // same as delete PantallaError
      PantallaError=NULL;

PantallaError->hide();
      PantallaError->deleteLater(); // same as delete PantallaError
      PantallaError=NULL;

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Here it leaves 300KB occupied.

Just when I finish the application the memory is released.