And another John Mayer dalliance bites the dust ... again. Katy Perry reportedly called it quits with the Mayer after he couldn't settle down.

"John just can’t commit, and he kept luring Katy back with promises that was going to change, but then he didn't," a source spilled to Radar Online. "Katy was pretty crazy about him, so she kept giving him another chance. John liked Katy, so he wanted to keep her in his life, but it just wasn't up to Katy’s standards," the source added.

What were Katy's standards? Don't forget, this is the girl who wrote Kelly Clarkson's 'I Do Not Hook Up' -- so you better believe she wants a boyfriend, not a booty call. Unfortunately, Mayer could only offer one of those things, and it wasn't the one she was looking for. "She needs the guy to be on board 100 percent and she was sick of John disappearing for five days at a time, then booty calling her, then straightening up and treating her well, only to go back to his old behavior a few days later."

"Finally she was like 'lose my number.'" Atta girl! As much as Perry loves bad boys, she only wants the ones she thinks she can tame.

This is the second time the pair have split. Previously, the 'Queen of California' singer dumped the 'California Gurl' songstress in an email -- that's cold! -- but they reunited shortly after, reportedly due to Perry's drunk texting, at a post MTV Video Music Awards date.

We're counting down the days til Katy and Taylor Swift have a girls' night to talk smack about J.M. It's only a matter of time!

Watch the Katy Perry 'Part of Me' Video