Increase -A default to 4MB
#16499 explains how the default allocation area is too small.
I've been now witness to at least 5 discussions on this top. Every discussion came to the conclusions that:
- The current default is too small
- It's unclear what the right default is.
We should not let perfect be the enemy of good and increase the default anyway. Based on my measurements in #16499 (comment 191032) I've chosen
4MB as the new default.
I also extended the user guide with points that:
- Parallel settings can benefit greatly from even higher allocation areas.
- Some settings can see regressions with higher settings.
- Small settings improve heap profile accuracy.