Or HaChaim on Genesis 41:56/אור החיים על בראשית מ״א:נ״ו

1 ויפתח יוסף את כל אשר בהם, Joseph opened all (the granaries) in which grain was stored. The reason that Joseph immediately opened all the silos instead of only the ones which were immediately needed was to see which ones contained grain that was capable of indefinite storage and which needed to be sold first in order that it should not deteriorate.

2Another reason why Joseph opened all the silos simultaneously was that he had arranged for the silos to be close to the various population centres. Had he opened only one silo at a time the people would have had to travel long distances to receive their rations. As it was, Joseph made sure the people knew that there was a supply of food close by. This made the famine a great deal easier to bear. Our rabbis have described this psychological fact by coining the phrase אינו דומה מי שיש לו פס בסלו למי שאין לו. "One cannot compare a person who has bread in his basket to someone whose basket is empty."

3Joseph may also have wanted the population to see for themselves the huge grain reserves he had accumulated so that they would not become concerned that his supply would be inadequate. In spite of all these confidence building measures taken by Joseph the Torah testifies that the famine grew severe almost at once.