Messages in this thread Patch in this message | | | Subject | Re: [PATCH 1/3] tracing,x86: add a TSC trace_clock; reset buffer on clock change | From | Steven Rostedt <> | Date | Tue, 11 Sep 2012 23:48:05 -0400 |
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On Tue, 2012-09-11 at 19:41 -0700, David Sharp wrote: > In order to promote interoperability between userspace tracers and ftrace, > add a trace_clock that reports raw TSC values which will then be recorded > in the ring buffer. Userspace tracers that also record TSCs are then on > exactly the same time base as the kernel and events can be unambiguously > interlaced. > > Tested: Enabled a tracepoint and the "tsc" trace_clock and saw very large > timestamp values. > > Google-Bug-Id: 6980623 > Signed-off-by: David Sharp <dhsharp@google.com> > --- > include/linux/trace_clock.h | 3 +++ > kernel/trace/trace.c | 3 +++ > kernel/trace/trace_clock.c | 16 ++++++++++++++++ > 3 files changed, 22 insertions(+), 0 deletions(-) > > diff --git a/include/linux/trace_clock.h b/include/linux/trace_clock.h > index 4eb4902..b86c7363 100644 > --- a/include/linux/trace_clock.h > +++ b/include/linux/trace_clock.h > @@ -16,5 +16,8 @@ extern u64 notrace trace_clock_local(void); > extern u64 notrace trace_clock(void); > extern u64 notrace trace_clock_global(void); > extern u64 notrace trace_clock_counter(void); > +#ifdef CONFIG_X86_TSC > +extern u64 notrace trace_clock_tsc(void); > +#endif > > #endif /* _LINUX_TRACE_CLOCK_H */ > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 5c38c81..dc1f1fa 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -480,6 +480,9 @@ static struct { > { trace_clock_local, "local" }, > { trace_clock_global, "global" }, > { trace_clock_counter, "counter" }, > +#ifdef CONFIG_X86_TSC > + { trace_clock_tsc, "tsc" }, > +#endif > };
I really hate adding arch defs in generic code. Perhaps what we could do is add a define here. Something like:
#ifndef ARCH_TRACE_CLOCKS # define ARCH_TRACE_CLOCKS #endif
[...] { trace_clock_counter, "counter" }, ARCH_TRACE_CLOCKS };
and have ARCH_TRACE_CLOCKS defined somewhere in an arch specific header. Not sure what header we could use though :-/
That is, in a header have:
#define ARCH_TRACE_CLOCKS \ { trace_clock_x86_tsc, "tsc" },
and also define trace_clock_x86_tsc in arch/x86/kernel...
-- Steve
> > int trace_clock_id; > diff --git a/kernel/trace/trace_clock.c b/kernel/trace/trace_clock.c > index 3947835..1770737 100644 > --- a/kernel/trace/trace_clock.c > +++ b/kernel/trace/trace_clock.c > @@ -125,3 +125,19 @@ u64 notrace trace_clock_counter(void) > { > return atomic64_add_return(1, &trace_counter); > } > + > +#ifdef CONFIG_X86_TSC > +/* > + * trace_clock_tsc(): A clock that is just the cycle counter. > + * > + * Unlike the other clocks, this is not in nanoseconds. > + */ > +u64 notrace trace_clock_tsc(void) > +{ > + u64 ret; > + rdtsc_barrier(); > + rdtscll(ret); > + > + return ret; > +} > +#endif
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