On Mon, 2013-05-06 at 13:34 +0530, Anshuman Khandual wrote:
> The 'to' field inside branch entries might contain stale values from previous
> PMU interrupt instances which had indirect branches. So clear all the values
> before reading a fresh set of BHRB entries after a PMU interrupt.
>
> Signed-off-by: Anshuman Khandual <khand...@linux.vnet.ibm.com>
> ---
> arch/powerpc/perf/core-book3s.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
> index c627843..09db68d 100644
> --- a/arch/powerpc/perf/core-book3s.c
> +++ b/arch/powerpc/perf/core-book3s.c
> @@ -1590,6 +1590,8 @@ static void record_and_restart(struct perf_event
> *event, unsigned long val,
> if (event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK) {
> struct cpu_hw_events *cpuhw;
> cpuhw = &__get_cpu_var(cpu_hw_events);
> + memset(cpuhw->bhrb_entries, 0,
> + sizeof(struct perf_branch_entry) *
> BHRB_MAX_ENTRIES);
> power_pmu_bhrb_read(cpuhw);
> data.br_stack = &cpuhw->bhrb_stack;
> }
Wouldn't it be just as effective, and less overhead, to set .to = 0; in
the else branch in power_pmu_bhrb_read() ?
eg:
diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index c627843..30af11a4 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -1516,6 +1516,7 @@ void power_pmu_bhrb_read(struct cpu_hw_events *cpuhw)
} else {
/* Update address, flags for current entry */
cpuhw->bhrb_entries[u_index].from = addr;
+ cpuhw->bhrb_entries[u_index].to = 0;
cpuhw->bhrb_entries[u_index].mispred = pred;
cpuhw->bhrb_entries[u_index].predicted = ~pred;
cheers
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
