On Tue, 15 Sep 2009, Uwe Kleine-König wrote: > On Tue, Sep 15, 2009 at 05:29:17PM +0200, Thomas Gleixner wrote: > > He, what is decreasing min_delta_ns ? There is no such code. > hrtimer_interrupt_hanging() can decrease min_delta_ns. > > Look at Bo's reports: min_delta_ns is initially 61036 and he gets > > hrtimer: interrupt too slow, forcing clock min delta to 52482 ns So the problem is that min delta is too small due to an unhandled 32bit overflow. But that's not a decrease by any means. It's simply an 32bit overflow bug which needs to be fixed. > > It ensures that the timer interrupts are delayed sufficiently that > > something else than the timer interrupt has a chance to get on the > > CPU. > Hhhhm, doesn't destroy that any upper bound for latency. If a process > succeeds to install many timers that expire one after another with a > short delta in between min_delta_ns goes up. This in turn mean that > even high priority processes loose the ability to sleep a short period. Yes, we know that already and it's on the list of things which need to be solved. Thanks, tglx
