Messages in this thread | | | Date | Wed, 8 Nov 2017 11:07:57 -0500 | From | Steven Rostedt <> | Subject | Re: [RFC PATCH v2] ftrace: support very early function tracing |
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On Wed, 8 Nov 2017 09:10:58 +0100 Peter Zijlstra <peterz@infradead.org> wrote:
> On Tue, Nov 07, 2017 at 09:17:06PM -0500, Steven Rostedt wrote: > > > +#ifdef CONFIG_X86_TSC > > > + entry->clock = rdtsc(); > > > +#else > > > + entry->clock = trace_clock_local(); > > > +#endif > > > > +#ifdef CONFIG_X86_TSC > > > + cpu_khz = native_calibrate_cpu(); > > > +#endif > > > > +#ifdef CONFIG_X86_TSC > > > + ns = cycles_to_ns(entry->clock, cpu_khz); > > > +#else > > > + ns = entry->clock; > > > +#endif > > Yeah, no, not going to happen...
Agreed.
What you can do is have an:
arch_early_trace_clock();
and in trace.c have:
u64 __weak arch_early_trace_clock(void) { return trace_clock_local(); }
u64 __weak arch_early_trace_clock_to_ns(u64 clock) { return clock; }
and in x86 have:
u64 arch_early_trace_clock(void) { return rdtsc(); }
u64 arch_early_trace_clock_to_ns(u64 clock) { return cycles_to_ns(clock, cpu_khz); }
Is that acceptable?
-- Steve
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