Messages in this thread | | | Date | Mon, 22 Jun 2009 17:40:30 +0200 | From | Ingo Molnar <> | Subject | Re: [patch 0/2] NOHZ vs. profile/oprofile v2 |
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* Martin Schwidefsky <schwidefsky@de.ibm.com> wrote:
> On Mon, 22 Jun 2009 17:29:37 +0200 > Ingo Molnar <mingo@elte.hu> wrote: > > > > > * Martin Schwidefsky <schwidefsky@de.ibm.com> wrote: > > > > > On Mon, 22 Jun 2009 17:05:53 +0200 > > > Ingo Molnar <mingo@elte.hu> wrote: > > > > > > > > > > > * Martin Schwidefsky <schwidefsky@de.ibm.com> wrote: > > > > > > > > > On Mon, 22 Jun 2009 16:41:10 +0200 > > > > > Ingo Molnar <mingo@elte.hu> wrote: > > > > > > > > > > > Hm, this is rather ugly. Why not use hrtimers like 'perf' does when > > > > > > it fallback-samples based on the timer tick? > > > > > > > > > > > > That method has three advantages: > > > > > > > > > > > > - no weird hookery needed > > > > > > - resolution can go far beyond HZ > > > > > > - it is evidently dynticks-safe > > > > > > > > > > Hmm, if we replace the HZ based oprofile tick with an hrtimer we > > > > > should add an interface to configure the sample interval as well, > > > > > no? Otherwise we just replace one timer event (HZ) with another > > > > > (hrtimer). > > > > > > > > Even if the hrtimer is set with a 1/HZ period it's a better > > > > solution, as it's dynticks safe without invasive changes. > > > > > > Ok, but the patch will be quite big. All the profile_tick() calls > > > from the architecture files will have to be removed. [...] > > > > Hey, that's a bonus :) > > It would remove some oddball code :-) > > > > [...] And if we really want to keep things separate there will be > > > two sets of per-cpu hrtimer, one for the old style profiler and > > > one for oprofile. Any preference for the user space interface to > > > set the sample rate? A sysctl? > > > > I dont think we want to keep things separate. Regarding old-style > > profiler, does anyone still use it? There's now a superior in-tree > > replacement for it, so we could phase it out. > > Well, for my part I won't miss it. But to be able to remove the > profile_tick() calls from the architectures I either have to rip > out the old profiler now, or adapt it to use hrtimer as well.
Do we _have to_ touch it so widely right now? We could start with a deprecation warning in this cycle. Once it's deprecated we can remove all those calls.
Ingo
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