A Mix of tech geeks and Hollywood stars — including Sean Parker, Leonardo DiCaprio and Matthew McConaughey — began flooding Austin, Texas, over the weekend for SXSW’s overlapping interactive conference and film festival. Parker did a Q&A with Al Gore yesterday, while Jonah Hill and Channing Tatum’s new comedy, “21 Jump Street,” debuted hours later. DiCaprio arrived fresh from the set of Quentin Tarantino’s “Django Unchained” with his Victoria’s Secret model girlfriend, Erin Heatherton, to attend a launch party for photo-sharing app Mobli on Saturday. And McConaughey showed his Texas roots at a premiere of “Killer Joe” by wearing a black cowboy hat and boots.