Messages in this thread | | | Date | Wed, 15 May 2013 18:55:42 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 1/2] nohz: Disable LOCKUP_DETECTOR when NO_HZ_FULL is enabled |
| |
On Wed, May 15, 2013 at 11:06:53AM -0400, Don Zickus wrote: > Coming into the middle of the thread is always hard, but why/how does perf > disable nohz_full? I didn't think the hardware events of perf would cause > problems as they are no different than an irq. Curious.
Yah, right :-) So I think what happens is that when we enter kernel space for whatever reason (say NMIs for a watchdog), we kill the magic NO_HZ state that allows a single task that's stuck in userspace to effectively have the tick disabled.
But yeah, the initial patch was a tad light on detail, so I'll have to let Steve and Frederic expand / correct.
| |