On Tue, 2012-07-17 at 00:27 -0400, Steven Rostedt wrote: > On Tue, 2012-07-17 at 06:18 +0200, Mike Galbraith wrote: > > > > > There's that too. But the issue I was talking about is with all trylock > > > loops. As holding an rt-mutex now disables migration, if a high priority > > > process preempts a task that holds the lock, and then the high prio task > > > starts spinning waiting for that lock to release, the lower priority > > > process will never get to run to release it. The cpu_chill() doesn't > > > help. > > > > Hrm. I better go make a testcase, this one definitely wants pounding > > through thick skull. > > Actually, I was mistaken. I forgot that we defined 'cpu_chill()' as > msleep(1) on RT, which would keep a deadlock from happening. Whew! There are no stars and moons on my pointy hat, just plain white cone, so you had me worried I was missing something critical there. > It doesn't explain the performance enhancement you get :-/ No, it doesn't. The only thing I can think of is that while folks are timed sleeping, they aren't preempting and interleaving IO as much, but I'm pulling that out of thin air. Timed sleep should be a lot longer than regular wakeup, so to my mind, there should be less interleave due to more thumb twiddling. -Mike -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
