From: Stephane Eranian <eran...@google.com> Sandy Bridge and Haswell support all required LBR filters natively, so there is no need to do instruction decoding in branch_type. This lowers the overhead of LBR sampling with filters.
We enable far calls for call, so calls include exceptions, but that seems like a acceptable trade off for much faster LBR sampling. [Description and changes from AK] Signed-off-by: Andi Kleen <a...@linux.intel.com> --- arch/x86/kernel/cpu/perf_event.h | 1 + arch/x86/kernel/cpu/perf_event_intel_lbr.c | 12 ++++++++---- 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h index 563d6e8..2341d9f 100644 --- a/arch/x86/kernel/cpu/perf_event.h +++ b/arch/x86/kernel/cpu/perf_event.h @@ -428,6 +428,7 @@ struct x86_pmu { u64 lbr_sel_mask; /* LBR_SELECT valid bits */ const int *lbr_sel_map; /* lbr_select mappings */ bool lbr_double_abort; /* duplicated lbr aborts */ + bool lbr_no_sw_filter; /* HW does all filters */ /* * Extra registers for events diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c index 33b6b5f..18f5a08 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c +++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c @@ -608,6 +608,9 @@ intel_pmu_lbr_filter(struct cpu_hw_events *cpuc) int i, j, type; bool compress = false; + if (x86_pmu.lbr_no_sw_filter) + return; + /* if sampling all branches, then nothing to filter */ if ((br_sel & X86_BR_ALL) == X86_BR_ALL) return; @@ -727,12 +730,13 @@ void intel_pmu_lbr_init_snb(void) x86_pmu.lbr_sel_mask = LBR_SEL_MASK; x86_pmu.lbr_sel_map = snb_lbr_sel_map; + x86_pmu.lbr_no_sw_filter = true; /* - * SW branch filter usage: - * - support syscall, sysret capture. - * That requires LBR_FAR but that means far - * jmp need to be filtered out + * We include interrupts/exceptions + * with calls. While technically they are not, + * it's not worth extra filtering just to + * get rid of them. */ pr_cont("16-deep LBR, "); } -- 1.7.7.6 -- 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/