path: root/arch/powerpc
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authorAnshuman Khandual <khandual@linux.vnet.ibm.com>2013-12-18 13:14:53 +1100
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2014-02-11 11:24:50 +1100
commitb4d6c06c8de81517320a9964b0c26e096aeadd7b (patch)
tree6386d39b3b83dbababfdb0c39b702f9513601734 /arch/powerpc
parent0ba3e1011660042dd3ea08ae8dbdc173352f3d47 (diff)
powerpc/perf: Configure BHRB filter before enabling PMU interrupts
Right now the config_bhrb() PMU specific call happens after write_mmcr0(), which actually enables the PMU for event counting and interrupts. So there is a small window of time where the PMU and BHRB runs without the required HW branch filter (if any) enabled in BHRB. This can cause some of the branch samples to be collected through BHRB without any filter applied and hence affects the correctness of the results. This patch moves the BHRB config function call before enabling interrupts. Here are some data points captured via trace prints which depicts how we could get PMU interrupts with BHRB filter NOT enabled with a standard perf record command line (asking for branch record information as well). $ perf record -j any_call ls Before the patch:- ls-1962 [003] d... 2065.299590: .perf_event_interrupt: MMCRA: 40000000000 ls-1962 [003] d... 2065.299603: .perf_event_interrupt: MMCRA: 40000000000 ... All the PMU interrupts before this point did not have the requested HW branch filter enabled in the MMCRA. ls-1962 [003] d... 2065.299647: .perf_event_interrupt: MMCRA: 40040000000 ls-1962 [003] d... 2065.299662: .perf_event_interrupt: MMCRA: 40040000000 After the patch:- ls-1850 [008] d... 190.311828: .perf_event_interrupt: MMCRA: 40040000000 ls-1850 [008] d... 190.311848: .perf_event_interrupt: MMCRA: 40040000000 All the PMU interrupts have the requested HW BHRB branch filter enabled in MMCRA. Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com> [mpe: Fixed up whitespace and cleaned up changelog] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc')
1 files changed, 3 insertions, 2 deletions
diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index 29b89e863d7c..67cf22083f4c 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -1147,6 +1147,9 @@ static void power_pmu_enable(struct pmu *pmu)
mmcr0 = ebb_switch_in(ebb, cpuhw->mmcr[0]);
+ if (cpuhw->bhrb_users)
+ ppmu->config_bhrb(cpuhw->bhrb_filter);
write_mmcr0(cpuhw, mmcr0);
@@ -1158,8 +1161,6 @@ static void power_pmu_enable(struct pmu *pmu)
- if (cpuhw->bhrb_users)
- ppmu->config_bhrb(cpuhw->bhrb_filter);

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