Messages in this thread Patch in this message | | | Date | Wed, 9 Nov 2022 08:38:31 +0530 | Subject | Re: [PATCH V5 6/7] arm64/perf: Add BRBE driver | From | Anshuman Khandual <> |
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On 11/7/22 11:55, Anshuman Khandual wrote: > +void arm64_pmu_brbe_read(struct pmu_hw_events *cpuc, struct perf_event *event) > +{ > + u64 brbinf; > + int idx; > + > + if (brbe_disabled(cpuc)) > + return; > + > + set_brbe_paused(); > + for (idx = 0; idx < cpuc->brbe_nr; idx++) { > + select_brbe_bank_index(idx); > + brbinf = get_brbinf_reg(idx); > + /* > + * There are no valid entries anymore on the buffer. > + * Abort the branch record processing to save some > + * cycles and also reduce the capture/process load > + * for the user space as well. > + */ > + if (brbe_invalid(brbinf)) > + break; > + > + if (brbe_valid(brbinf)) { > + cpuc->branches->brbe_entries[idx].from = get_brbsrc_reg(idx); > + cpuc->branches->brbe_entries[idx].to = get_brbtgt_reg(idx); > + } else if (brbe_source(brbinf)) { > + cpuc->branches->brbe_entries[idx].from = get_brbsrc_reg(idx); > + cpuc->branches->brbe_entries[idx].to = 0; > + } else if (brbe_target(brbinf)) { > + cpuc->branches->brbe_entries[idx].from = 0; > + cpuc->branches->brbe_entries[idx].to = get_brbtgt_reg(idx); > + } > + capture_brbe_flags(cpuc, event, brbinf, idx); > + } > + cpuc->branches->brbe_stack.nr = idx; > + cpuc->branches->brbe_stack.hw_idx = -1ULL; > + process_branch_aborts(cpuc); > +}
The following additional changes are required to ensure that BRBE remains "un-paused" after processing the branch records inside PMU interrupt handler. Without this change, there will PMU interrupts without valid branch records, reducing branch stack sample collection during given workload execution. I will fold this into the BRBE driver.
diff --git a/drivers/perf/arm_pmu_brbe.c b/drivers/perf/arm_pmu_brbe.c index ce1aa4171481..c8154ddd341d 100644 --- a/drivers/perf/arm_pmu_brbe.c +++ b/drivers/perf/arm_pmu_brbe.c @@ -429,6 +429,7 @@ void arm64_pmu_brbe_read(struct pmu_hw_events *cpuc, struct perf_event *event) cpuc->branches->brbe_stack.nr = idx; cpuc->branches->brbe_stack.hw_idx = -1ULL; process_branch_aborts(cpuc); + clr_brbe_paused(); } void arm64_pmu_brbe_reset(struct pmu_hw_events *cpuc) diff --git a/drivers/perf/arm_pmu_brbe.h b/drivers/perf/arm_pmu_brbe.h index 22c4b25b1777..33da6fc9aefa 100644 --- a/drivers/perf/arm_pmu_brbe.h +++ b/drivers/perf/arm_pmu_brbe.h @@ -257,3 +257,11 @@ static inline void set_brbe_paused(void) write_sysreg_s(brbfcr | BRBFCR_EL1_PAUSED, SYS_BRBFCR_EL1); isb(); } + +static inline void clr_brbe_paused(void) +{ + u64 brbfcr = read_sysreg_s(SYS_BRBFCR_EL1); + + write_sysreg_s(brbfcr & ~BRBFCR_EL1_PAUSED, SYS_BRBFCR_EL1); + isb(); +} For example:
./perf record -j any,u,k,save_type ls ./perf report -D | grep branch Before this change -
# cat out | grep "branch stack: nr:64" | wc -l 4 # cat out | grep "branch stack: nr:0" | wc -l 57 # perf report -D | grep branch ... branch stack: nr:64 ... branch stack: nr:0 ... branch stack: nr:64 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:64 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:64 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0 ... branch stack: nr:0
But after this change -
$ cat out | grep "branch stack: nr:64" | wc -l 107 # cat out | grep "branch stack: nr:0" | wc -l 0 $ perf report -D | grep branch ....................... ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64 ... branch stack: nr:64
....................... - Anshuman
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