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SubjectRe: [PATCH 0/1] x86: Eliminate bp argument from the stack tracing routines
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Frederic Weisbecker <fweisbec@gmail.com> writes:

> > (FWIW, this
> >
> > diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
> > index 461a85d..d977d26 100644
> > --- a/arch/x86/kernel/cpu/perf_event.c
> > +++ b/arch/x86/kernel/cpu/perf_event.c
> > @@ -1653,7 +1653,7 @@ static const struct stacktrace_ops backtrace_ops = {
> > .warning_symbol = backtrace_warning_symbol,
> > .stack = backtrace_stack,
> > .address = backtrace_address,
> > - .walk_stack = print_context_stack_bp,
> > + .walk_stack = print_context_stack,
> > };
> >
> > makes it produce correct kernel callchains. And yes, I did compile the
> > kernel with CONFIG_FRAME_POINTER).
>
>
>
> What do you see is broken in 64 bits perf callchains? Can you please provide
> me more details so that I can fix the issue?

Apparently, the problem only happens when using the hrtimer based
events. I don't think there is a way to make perf use those from the
command line, but if you apply this:

--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -294,6 +294,12 @@ static void create_counter(int counter, int cpu)
attr->enable_on_exec = 1;
}

+ if (attr->config == PERF_COUNT_HW_CPU_CYCLES && attr->type ==
PERF_TYPE_HARDWARE)
+ {
+ attr->type = PERF_TYPE_SOFTWARE;
+ attr->config = PERF_COUNT_SW_CPU_CLOCK;
+ }
+
for (thread_index = 0; thread_index < thread_num; thread_index++) {
try_again:
fd[nr_cpu][counter][thread_index] = sys_perf_event_open(attr,
you should be able to see the problem. You can also try sysprof; it
always uses the software counters.


Soren


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