After a strong start, a few hiccups, and a somewhat listless finale, the Grammy-nominated new mom declared at the end of her hour-long set in the desert that “next time I’m back in the tent.”  “I want to be in the sweat,” she said. M.I.A. had performed twice in smaller tents at the music festival, in its tenth year and one of the nation’s most prestigious. She noted earlier, “I really don’t know how to bring it on the main stage.” And her live show staples — climbing on speakers, dancing body-to-body with the crowd — didn’t quite fit the new digs. When she tried to bring some of the audience onstage Saturday night, security guards thwarted most fans.  M.I.A. ended up on a platform above the crowd performing “Bird Flu,” and asked when it was over: “Can we get some order in the place? My baby’s waiting.” She gave birth to a son in February, a few days after the Grammys. The Killers took the main stage to close the evening. The Las Vegas-based group, who began with their most recent single “Human,” appeared far more comfortable in the setting.  Wearing a black No Limit Records T-shirt, sneakers and jeans with Day-Glo green lining, M.I.A. performed songs from her two most recent albums and gave up the spotlight to Baltimore-based protege Rye Rye for a song. While she moved alongside Day-Glo-clad dancers for a lively opening number, she stood stiffly at other times behind a podium adorned with microphones as if at a news conference.  Roaming into the audience with help of a piggyback ride, she finished with crowd favorite “Paper Planes,” lifted to hit status by appearances in “Pineapple Express” and “Slumdog Millionaire.”  But the British-born, Sri-Lankan-bred rapper pushed back against Hollywood. She slyly referenced her status as Coachella replacement for Amy Winehouse, who canceled due to visa trouble, by singing “They tried to make me do the Oscars. I said no, no, no.”  And, she noted, “I want to let you know that just ‘cuz I did the Grammys, it doesn’t mean I’ve gone all sold out.”  Though she wasn’t embracing Hollywood, some of its regulars certainly wanted to be around for her. Zac Efron was seen ducking out of the fest’s VIP area in the afternoon Saturday, and Paris Hilton posed for pictures with her new boyfriend during Thievery Corporation’s popular main stage set just before M.I.A.  Also performing Saturday were Joss Stone, TV On The Radio, Fleet Foxes — who apologized to fans after suffering repeated technical problems — and Travis Barker and DJ AM, who had the dance tent crowd roaring at their drum-assisted remixes of pop hits.  Exact figures weren’t released but crowds at the three-day festival appear to have more than doubled the approximate 75,000 population of this community southeast of Palm Springs. Police reported 17 arrests Saturday and fire officials said two people had been taken to hospitals. Temperatures, climbing throughout the fest, were expected to hit the high 90s on Sunday, which features the Yeah Yeah Yeahs, Public Enemy, My Bloody Valentine and the Cure.