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SubjectRe: [PATCH 3/6] perf: Use sample_flags for branch stack
On Wed, Aug 31, 2022 at 07:55:11AM -0700, kan.liang@linux.intel.com wrote:
> From: Kan Liang <kan.liang@linux.intel.com>
>
> Use the new sample_flags to indicate whether the branch stack is filled
> by the PMU driver.
>
> Remove the br_stack from the perf_sample_data_init() to minimize the number
> of cache lines touched.
>
> Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
> ---
> arch/powerpc/perf/core-book3s.c | 1 +
> arch/x86/events/core.c | 4 +++-
> arch/x86/events/intel/core.c | 4 +++-
> arch/x86/events/intel/ds.c | 5 ++++-
> include/linux/perf_event.h | 4 ++--
> kernel/events/core.c | 4 ++--
> 6 files changed, 15 insertions(+), 7 deletions(-)

Looks like you need to update AMD LBR code in amd_pmu_v2_handle_irq().

Thanks,
Namhyung

>
> diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
> index 13919eb96931..1ad1efdb33f9 100644
> --- a/arch/powerpc/perf/core-book3s.c
> +++ b/arch/powerpc/perf/core-book3s.c
> @@ -2297,6 +2297,7 @@ static void record_and_restart(struct perf_event *event, unsigned long val,
> cpuhw = this_cpu_ptr(&cpu_hw_events);
> power_pmu_bhrb_read(event, cpuhw);
> data.br_stack = &cpuhw->bhrb_stack;
> + data.sample_flags |= PERF_SAMPLE_BRANCH_STACK;
> }
>
> if (event->attr.sample_type & PERF_SAMPLE_DATA_SRC &&
> diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
> index f969410d0c90..bb34a28fa71b 100644
> --- a/arch/x86/events/core.c
> +++ b/arch/x86/events/core.c
> @@ -1714,8 +1714,10 @@ int x86_pmu_handle_irq(struct pt_regs *regs)
>
> perf_sample_data_init(&data, 0, event->hw.last_period);
>
> - if (has_branch_stack(event))
> + if (has_branch_stack(event)) {
> data.br_stack = &cpuc->lbr_stack;
> + data.sample_flags |= PERF_SAMPLE_BRANCH_STACK;
> + }
>
> if (perf_event_overflow(event, &data, regs))
> x86_pmu_stop(event, 0);
> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
> index 4fce2bdbbf87..36f95894dd1c 100644
> --- a/arch/x86/events/intel/core.c
> +++ b/arch/x86/events/intel/core.c
> @@ -3004,8 +3004,10 @@ static int handle_pmi_common(struct pt_regs *regs, u64 status)
>
> perf_sample_data_init(&data, 0, event->hw.last_period);
>
> - if (has_branch_stack(event))
> + if (has_branch_stack(event)) {
> data.br_stack = &cpuc->lbr_stack;
> + data.sample_flags |= PERF_SAMPLE_BRANCH_STACK;
> + }
>
> if (perf_event_overflow(event, &data, regs))
> x86_pmu_stop(event, 0);
> diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
> index 3af24c4891fb..d5f3007af59d 100644
> --- a/arch/x86/events/intel/ds.c
> +++ b/arch/x86/events/intel/ds.c
> @@ -1645,8 +1645,10 @@ static void setup_pebs_fixed_sample_data(struct perf_event *event,
> data->sample_flags |= PERF_SAMPLE_TIME;
> }
>
> - if (has_branch_stack(event))
> + if (has_branch_stack(event)) {
> data->br_stack = &cpuc->lbr_stack;
> + data->sample_flags |= PERF_SAMPLE_BRANCH_STACK;
> + }
> }
>
> static void adaptive_pebs_save_regs(struct pt_regs *regs,
> @@ -1796,6 +1798,7 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
> if (has_branch_stack(event)) {
> intel_pmu_store_pebs_lbrs(lbr);
> data->br_stack = &cpuc->lbr_stack;
> + data->sample_flags |= PERF_SAMPLE_BRANCH_STACK;
> }
> }
>
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index b0ebbb1377b9..2aec1765b3d5 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -1010,7 +1010,6 @@ struct perf_sample_data {
> u64 sample_flags;
> u64 addr;
> struct perf_raw_record *raw;
> - struct perf_branch_stack *br_stack;
> u64 period;
> union perf_sample_weight weight;
> u64 txn;
> @@ -1020,6 +1019,8 @@ struct perf_sample_data {
> * The other fields, optionally {set,used} by
> * perf_{prepare,output}_sample().
> */
> + struct perf_branch_stack *br_stack;
> +
> u64 type;
> u64 ip;
> struct {
> @@ -1060,7 +1061,6 @@ static inline void perf_sample_data_init(struct perf_sample_data *data,
> data->sample_flags = 0;
> data->addr = addr;
> data->raw = NULL;
> - data->br_stack = NULL;
> data->period = period;
> data->weight.full = 0;
> data->data_src.val = PERF_MEM_NA;
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index c9b9cb79231a..104c0c9f4e6f 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -7052,7 +7052,7 @@ void perf_output_sample(struct perf_output_handle *handle,
> }
>
> if (sample_type & PERF_SAMPLE_BRANCH_STACK) {
> - if (data->br_stack) {
> + if (data->sample_flags & PERF_SAMPLE_BRANCH_STACK) {
> size_t size;
>
> size = data->br_stack->nr
> @@ -7358,7 +7358,7 @@ void perf_prepare_sample(struct perf_event_header *header,
>
> if (sample_type & PERF_SAMPLE_BRANCH_STACK) {
> int size = sizeof(u64); /* nr */
> - if (data->br_stack) {
> + if (data->sample_flags & PERF_SAMPLE_BRANCH_STACK) {
> if (perf_sample_save_hw_index(event))
> size += sizeof(u64);
>
> --
> 2.35.1
>
>

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