No one really knew whether M.I.A. was going to show up for her Bonnaroo performance. Days before her set, the Sri Lankan MC announced that she was canceling her European tour due to exhaustion. But as soon as the dubby beat of “Bamboo Banga” kicked off, it was clear she didn’t duck out of her commitment. “This is my last show,” she shouted during her set. “And I’m glad that I’m spending it with all my hippies!” She may be exhausted from constant touring, but M.I.A. delivered a mind-blowing set of ass-shaking jungle-disco tonight, which included crowd favorites like “Bucky Done Gun,” “Paper Planes,” and “Galang.” Her energy was boundless: wearing nothing more than a day-glo orange T-shirt and white-sequined hot pants, she prowled all over the stage, manned the DJ decks, sounded her air horn and climbed on top of the rattling stacks of speakers. The crowd was equally stoked: mid-way through, the tent erupted into an anarchic dance party, with sweaty fans climbing over the barriers to join her and the crew onstage for jams like horn-heavy bhangra groove “Boyz” and the Bollywood-funk number “Jimmy.” The energy never waned, even when the kids were kicked off the stage. M.I.A. wrapped up the set with her controversial hit “Paper Planes.” As the sounds of gunshot samples resounded through the tent, the crowd jubilantly pumped their fists to each shot. A strangely awesome moment — and one of the best so far of the festival.