Slow LDIF/CSV export

When exporting many entries to LDIF or CSV I notice the following:

The progress bar gets to 50% while counting the number of exported entries, in this case it tells me Exported 29048 entries (which is the number of entries I got in as the search result so it should be done) and then it just sits there for 10-15 minutes. Minimal CPU activity so it doesn't seem as it's doing anything.