Messages in this thread | | | Date | Mon, 16 Oct 2023 13:48:25 -0400 | Subject | Re: [PATCH V4 1/7] perf: Add branch stack counters | From | "Liang, Kan" <> |
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Hi Peter,
Could you please share your comments for this series?
Thanks, Kan
On 2023-10-04 2:40 p.m., kan.liang@linux.intel.com wrote: > From: Kan Liang <kan.liang@linux.intel.com> > > Currently, the additional information of a branch entry is stored in a > u64 space. With more and more information added, the space is running > out. For example, the information of occurrences of events will be added > for each branch. > > Two places were suggested to append the counters. > https://lore.kernel.org/lkml/20230802215814.GH231007@hirez.programming.kicks-ass.net/ > One place is right after the flags of each branch entry. It changes the > existing struct perf_branch_entry. The later ARCH specific > implementation has to be really careful to consistently pick > the right struct. > The other place is right after the entire struct perf_branch_stack. > The disadvantage is that the pointer of the extra space has to be > recorded. The common interface perf_sample_save_brstack() has to be > updated. > > The latter is much straightforward, and should be easily understood and > maintained. It is implemented in the patch. > > Add a new branch sample type, PERF_SAMPLE_BRANCH_COUNTERS, to indicate > the event which is recorded in the branch info. > > The "u64 counters" may store the occurrences of several events. The > information regarding the number of events/counters and the width of > each counter should be exposed via sysfs as a reference for the perf > tool. Define the branch_counter_nr and branch_counter_width ABI here. > The support will be implemented later in the Intel-specific patch. > > Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org> > Signed-off-by: Kan Liang <kan.liang@linux.intel.com> > Cc: Sandipan Das <sandipan.das@amd.com> > Cc: Ravi Bangoria <ravi.bangoria@amd.com> > Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com> > --- > > Changes since V3: > - Add a new branch sample type, PERF_SAMPLE_BRANCH_COUNTERS > Drop the two branch sample type in V2. > - Add the branch_counter_nr and branch_counter_width ABI > > .../testing/sysfs-bus-event_source-devices-caps | 6 ++++++ > arch/powerpc/perf/core-book3s.c | 2 +- > arch/x86/events/amd/core.c | 2 +- > arch/x86/events/core.c | 2 +- > arch/x86/events/intel/core.c | 2 +- > arch/x86/events/intel/ds.c | 4 ++-- > include/linux/perf_event.h | 17 ++++++++++++++++- > include/uapi/linux/perf_event.h | 10 ++++++++++ > kernel/events/core.c | 8 ++++++++ > 9 files changed, 46 insertions(+), 7 deletions(-) > > diff --git a/Documentation/ABI/testing/sysfs-bus-event_source-devices-caps b/Documentation/ABI/testing/sysfs-bus-event_source-devices-caps > index 8757dcf41c08..451f0c620aa7 100644 > --- a/Documentation/ABI/testing/sysfs-bus-event_source-devices-caps > +++ b/Documentation/ABI/testing/sysfs-bus-event_source-devices-caps > @@ -16,3 +16,9 @@ Description: > Example output in powerpc: > grep . /sys/bus/event_source/devices/cpu/caps/* > /sys/bus/event_source/devices/cpu/caps/pmu_name:POWER9 > + > + The "branch_counter_nr" in the supported platform exposes the > + maximum number of counters which can be shown in the u64 counters > + of PERF_SAMPLE_BRANCH_COUNTERS, while the "branch_counter_width" > + exposes the width of each counter. Both of them can be used by > + the perf tool to parse the logged counters in each branch. > diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c > index 8c1f7def596e..3c14596bbfaf 100644 > --- a/arch/powerpc/perf/core-book3s.c > +++ b/arch/powerpc/perf/core-book3s.c > @@ -2313,7 +2313,7 @@ static void record_and_restart(struct perf_event *event, unsigned long val, > struct cpu_hw_events *cpuhw; > cpuhw = this_cpu_ptr(&cpu_hw_events); > power_pmu_bhrb_read(event, cpuhw); > - perf_sample_save_brstack(&data, event, &cpuhw->bhrb_stack); > + perf_sample_save_brstack(&data, event, &cpuhw->bhrb_stack, NULL); > } > > if (event->attr.sample_type & PERF_SAMPLE_DATA_SRC && > diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c > index e24976593a29..4ee6390b45c9 100644 > --- a/arch/x86/events/amd/core.c > +++ b/arch/x86/events/amd/core.c > @@ -940,7 +940,7 @@ static int amd_pmu_v2_handle_irq(struct pt_regs *regs) > continue; > > if (has_branch_stack(event)) > - perf_sample_save_brstack(&data, event, &cpuc->lbr_stack); > + perf_sample_save_brstack(&data, event, &cpuc->lbr_stack, NULL); > > if (perf_event_overflow(event, &data, regs)) > x86_pmu_stop(event, 0); > diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c > index 40ad1425ffa2..40c9af124128 100644 > --- a/arch/x86/events/core.c > +++ b/arch/x86/events/core.c > @@ -1702,7 +1702,7 @@ int x86_pmu_handle_irq(struct pt_regs *regs) > perf_sample_data_init(&data, 0, event->hw.last_period); > > if (has_branch_stack(event)) > - perf_sample_save_brstack(&data, event, &cpuc->lbr_stack); > + perf_sample_save_brstack(&data, event, &cpuc->lbr_stack, NULL); > > 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 a08f794a0e79..41a164764a84 100644 > --- a/arch/x86/events/intel/core.c > +++ b/arch/x86/events/intel/core.c > @@ -3047,7 +3047,7 @@ 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)) > - perf_sample_save_brstack(&data, event, &cpuc->lbr_stack); > + perf_sample_save_brstack(&data, event, &cpuc->lbr_stack, NULL); > > 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 bf97ab904d40..cb3f329f8fa4 100644 > --- a/arch/x86/events/intel/ds.c > +++ b/arch/x86/events/intel/ds.c > @@ -1755,7 +1755,7 @@ static void setup_pebs_fixed_sample_data(struct perf_event *event, > setup_pebs_time(event, data, pebs->tsc); > > if (has_branch_stack(event)) > - perf_sample_save_brstack(data, event, &cpuc->lbr_stack); > + perf_sample_save_brstack(data, event, &cpuc->lbr_stack, NULL); > } > > static void adaptive_pebs_save_regs(struct pt_regs *regs, > @@ -1912,7 +1912,7 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event, > > if (has_branch_stack(event)) { > intel_pmu_store_pebs_lbrs(lbr); > - perf_sample_save_brstack(data, event, &cpuc->lbr_stack); > + perf_sample_save_brstack(data, event, &cpuc->lbr_stack, NULL); > } > } > > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > index e85cd1c0eaf3..9ad79f8107cb 100644 > --- a/include/linux/perf_event.h > +++ b/include/linux/perf_event.h > @@ -1138,6 +1138,10 @@ static inline bool branch_sample_priv(const struct perf_event *event) > return event->attr.branch_sample_type & PERF_SAMPLE_BRANCH_PRIV_SAVE; > } > > +static inline bool branch_sample_counters(const struct perf_event *event) > +{ > + return event->attr.branch_sample_type & PERF_SAMPLE_BRANCH_COUNTERS; > +} > > struct perf_sample_data { > /* > @@ -1172,6 +1176,7 @@ struct perf_sample_data { > struct perf_callchain_entry *callchain; > struct perf_raw_record *raw; > struct perf_branch_stack *br_stack; > + u64 *br_stack_cntr; > union perf_sample_weight weight; > union perf_mem_data_src data_src; > u64 txn; > @@ -1249,7 +1254,8 @@ static inline void perf_sample_save_raw_data(struct perf_sample_data *data, > > static inline void perf_sample_save_brstack(struct perf_sample_data *data, > struct perf_event *event, > - struct perf_branch_stack *brs) > + struct perf_branch_stack *brs, > + u64 *brs_cntr) > { > int size = sizeof(u64); /* nr */ > > @@ -1257,7 +1263,16 @@ static inline void perf_sample_save_brstack(struct perf_sample_data *data, > size += sizeof(u64); > size += brs->nr * sizeof(struct perf_branch_entry); > > + /* > + * The extension space for counters is appended after the > + * struct perf_branch_stack. It is used to store the occurrences > + * of events of each branch. > + */ > + if (brs_cntr) > + size += brs->nr * sizeof(u64); > + > data->br_stack = brs; > + data->br_stack_cntr = brs_cntr; > data->dyn_size += size; > data->sample_flags |= PERF_SAMPLE_BRANCH_STACK; > } > diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h > index 39c6a250dd1b..4461f380425b 100644 > --- a/include/uapi/linux/perf_event.h > +++ b/include/uapi/linux/perf_event.h > @@ -204,6 +204,8 @@ enum perf_branch_sample_type_shift { > > PERF_SAMPLE_BRANCH_PRIV_SAVE_SHIFT = 18, /* save privilege mode */ > > + PERF_SAMPLE_BRANCH_COUNTERS_SHIFT = 19, /* save occurrences of events on a branch */ > + > PERF_SAMPLE_BRANCH_MAX_SHIFT /* non-ABI */ > }; > > @@ -235,6 +237,8 @@ enum perf_branch_sample_type { > > PERF_SAMPLE_BRANCH_PRIV_SAVE = 1U << PERF_SAMPLE_BRANCH_PRIV_SAVE_SHIFT, > > + PERF_SAMPLE_BRANCH_COUNTERS = 1U << PERF_SAMPLE_BRANCH_COUNTERS_SHIFT, > + > PERF_SAMPLE_BRANCH_MAX = 1U << PERF_SAMPLE_BRANCH_MAX_SHIFT, > }; > > @@ -982,6 +986,12 @@ enum perf_event_type { > * { u64 nr; > * { u64 hw_idx; } && PERF_SAMPLE_BRANCH_HW_INDEX > * { u64 from, to, flags } lbr[nr]; > + * # > + * # The format of the counters is decided by the > + * # "branch_counter_nr" and "branch_counter_width", > + * # which are defined in the ABI. > + * # > + * { u64 counters; } cntr[nr] && PERF_SAMPLE_BRANCH_COUNTERS > * } && PERF_SAMPLE_BRANCH_STACK > * > * { u64 abi; # enum perf_sample_regs_abi > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 41e28f64a4a9..56b08ffeed2f 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -7336,6 +7336,14 @@ void perf_output_sample(struct perf_output_handle *handle, > if (branch_sample_hw_index(event)) > perf_output_put(handle, data->br_stack->hw_idx); > perf_output_copy(handle, data->br_stack->entries, size); > + /* > + * Add the extension space which is appended > + * right after the struct perf_branch_stack. > + */ > + if (data->br_stack_cntr) { > + size = data->br_stack->nr * sizeof(u64); > + perf_output_copy(handle, data->br_stack_cntr, size); > + } > } else { > /* > * we always store at least the value of nr
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