Messages in this thread | | | Subject | Re: [PATCH 2/3] perf_counter: allow arch to supply event misc flags and instruction pointer | From | Peter Zijlstra <> | Date | Thu, 14 May 2009 08:45:34 +0200 |
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On Thu, 2009-05-14 at 13:29 +1000, Paul Mackerras wrote: > At present the values we put in overflow events for the misc flags > indicating processor mode and the instruction pointer are obtained > using the standard user_mode() and instruction_pointer() functions. > Those functions tell you where the performance monitor interrupt > was taken, which might not be exactly where the counter overflow > occurred, for example because interrupts were disabled at the point > where the overflow occurred, or because the processor had many > instructions in flight and chose to complete some more instructions > beyond the one that caused the counter overflow. > > Some architectures (e.g. powerpc) can supply more precise information > about where the counter overflow occurred and the processor mode at > that point. This introduces new functions, perf_misc_flags() and > perf_instruction_pointer(), which arch code can override to provide > more precise information if available. They have default implementations > which are identical to the existing code. > > This also adds a new misc flag value, PERF_EVENT_MISC_HYPERVISOR, for > the case where a counter overflow occurred in the hypervisor. > > Signed-off-by: Paul Mackerras <paulus@samba.org> > --- > include/linux/perf_counter.h | 7 +++++++ > kernel/perf_counter.c | 5 ++--- > 2 files changed, 9 insertions(+), 3 deletions(-) > > diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h > index 614f921..2b12d98 100644 > --- a/include/linux/perf_counter.h > +++ b/include/linux/perf_counter.h > @@ -213,6 +213,7 @@ struct perf_counter_mmap_page { > #define PERF_EVENT_MISC_KERNEL (1 << 0) > #define PERF_EVENT_MISC_USER (1 << 1) > #define PERF_EVENT_MISC_OVERFLOW (1 << 2) > +#define PERF_EVENT_MISC_HYPERVISOR (1 << 3)
Ah, I think I've taught userspace that either !USER && !KERNEL or USER && KERNEL is HV information, since neither really makes sense :-)
> struct perf_event_header { > __u32 type; > @@ -588,6 +589,12 @@ extern int sysctl_perf_counter_mlock; > > extern void perf_counter_init(void); > > +#ifndef perf_misc_flags > +#define perf_misc_flags(regs) (user_mode(regs) ? PERF_EVENT_MISC_USER : \ > + PERF_EVENT_MISC_KERNEL) > +#define perf_instruction_pointer(regs) instruction_pointer(regs) > +#endif > + > #else > static inline void > perf_counter_task_sched_in(struct task_struct *task, int cpu) { } > diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c > index ff166c1..89568de 100644 > --- a/kernel/perf_counter.c > +++ b/kernel/perf_counter.c > @@ -1978,11 +1978,10 @@ static void perf_counter_output(struct perf_counter *counter, > header.size = sizeof(header); > > header.misc = PERF_EVENT_MISC_OVERFLOW; > - header.misc |= user_mode(regs) ? > - PERF_EVENT_MISC_USER : PERF_EVENT_MISC_KERNEL; > + header.misc |= perf_misc_flags(regs); > > if (record_type & PERF_RECORD_IP) { > - ip = instruction_pointer(regs); > + ip = perf_instruction_pointer(regs); > header.type |= PERF_RECORD_IP; > header.size += sizeof(ip); > }
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