Messages in this thread | | | Date | Wed, 05 May 2010 15:09:14 +0200 | From | Tejun Heo <> | Subject | Re: [RFC PATCHSET] sched,perf: unify tracers in sched and move perf on top of TP |
| |
Hello,
On 05/05/2010 02:33 PM, Avi Kivity wrote: > On 05/05/2010 02:38 PM, Peter Zijlstra wrote: >> As it stands I'd argue to simply drop this whole idea. The SCHED_EVENT() >> thing doesn't look like its worth the obfuscation and I'm very much >> opposed to making perf and sched_notifiers rely on tracepoints. > > We can make perf rely on sched_notifiers, I think it's exactly the same > case as kvm - extra cpu state that needs switching at context switch > time. We could also make fpu switching use sched_notifiers, but that's > pushing it a bit.
Oh, that was my first attempt too. The difference between TPs and sched_notifiers is the enable condition. TP is system-wide while sched_notifier is per-task. The thing is that for perf hooks, system-wide enable condition works much better. Also, w/ sched_notifiers, there's the problem that no one else but self can enable/disable it (which can be changed but doing it without causing call time overhead requires a bit of effort).
Thanks.
-- tejun
| |