I sometimes browse through the bugzilla to check over recent bugs to find if any of them are related to me. After the update, I decided to look up bugzilla to check if I am encountering a common problem. And, Bingo! The very first bug was about KDM slowing down. There was a suggestion about updating font cache to avoid slow startup of KDM. It can be done using the following command:
I tried it and the next time KDM was loaded very fast indeed. The bug was closed by the Arch linux maintainer with the following comment: "Some font package (maybe unofficial) doesn't run fc-cache after its installation or its removal." However, I think a deeper investigation should be made before closing the bug. I have been a number of instances in Arch linux bugzilla when the bug is closed without sufficient investigation. Arch developers pass the buck to upstream developers very fast.