Messages in this thread | | | Date | Wed, 24 Aug 2022 15:14:45 -0400 | Subject | Re: [BUG] perf/x86/intel/pebs: PEBS timestamps overwritten | From | "Liang, Kan" <> |
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On 2022-08-24 5:27 a.m., Peter Zijlstra wrote: > > Should be 3 patches at the very least I think, the first one introducing > the new field and then follow up patches making use of it. > > And yes as Ravi mentions there's the CALLCHAIN_EARLY hack that could be > cleaned up as well, making it 4 or something. > > On Fri, Aug 05, 2022 at 09:36:37AM -0400, Liang, Kan wrote: > >> diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c >> index 34be3bc5151a..a2c26eaeb0d9 100644 >> --- a/arch/x86/events/intel/ds.c >> +++ b/arch/x86/events/intel/ds.c >> @@ -1687,8 +1687,10 @@ static void setup_pebs_fixed_sample_data(struct >> perf_event *event, >> * We can only do this for the default trace clock. >> */ >> if (x86_pmu.intel_cap.pebs_format >= 3 && >> - event->attr.use_clockid == 0) >> + event->attr.use_clockid == 0) { > > Indent fail; please add: 'set cino=(0:0' to your .vimrc or figure out > the equivalent for your editor of choice. > >> data->time = native_sched_clock_from_tsc(pebs->tsc); >> + data->flags |= PERF_SAMPLE_DATA_TIME; >> + } >> >> if (has_branch_stack(event)) >> data->br_stack = &cpuc->lbr_stack; > >> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h >> index da759560eec5..33054bf31fc1 100644 >> --- a/include/linux/perf_event.h >> +++ b/include/linux/perf_event.h >> @@ -999,6 +999,7 @@ int perf_event_read_local(struct perf_event *event, >> u64 *value, >> extern u64 perf_event_read_value(struct perf_event *event, >> u64 *enabled, u64 *running); >> >> +#define PERF_SAMPLE_DATA_TIME 0x1 >> >> struct perf_sample_data { >> /* >> @@ -1012,6 +1013,7 @@ struct perf_sample_data { >> union perf_sample_weight weight; >> u64 txn; >> union perf_mem_data_src data_src; >> + u64 flags; >> >> /* >> * The other fields, optionally {set,used} by > > How about we call that 'sample_flags' instead and use PERF_SAMPLE_* as > we already have, something like so:
True, I think we can use PERF_SAMPLE_* and avoid adding more flags.
I will implement some patches based on the suggestion.
Thanks, Kan
> > > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > index ee8b9ecdc03b..b0ebbb1377b9 100644 > --- a/include/linux/perf_event.h > +++ b/include/linux/perf_event.h > @@ -1007,6 +1007,7 @@ struct perf_sample_data { > * Fields set by perf_sample_data_init(), group so as to > * minimize the cachelines touched. > */ > + u64 sample_flags; > u64 addr; > struct perf_raw_record *raw; > struct perf_branch_stack *br_stack; > @@ -1056,6 +1057,7 @@ static inline void perf_sample_data_init(struct perf_sample_data *data, > u64 addr, u64 period) > { > /* remaining struct members initialized in perf_prepare_sample() */ > + data->sample_flags = 0; > data->addr = addr; > data->raw = NULL; > data->br_stack = NULL; > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 2621fd24ad26..fed447f59024 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -6792,15 +6792,21 @@ static void perf_aux_sample_output(struct perf_event *event, > ring_buffer_put(rb); > } > > -static void __perf_event_header__init_id(struct perf_event_header *header, > - struct perf_sample_data *data, > - struct perf_event *event) > +static u64 __perf_event_header__init_id(struct perf_event_header *header, > + struct perf_sample_data *data, > + struct perf_event *event) > { > u64 sample_type = event->attr.sample_type; > > data->type = sample_type; > header->size += event->id_header_size; > > + /* > + * Clear the sample flags that have already been done by the > + * PMU driver. > + */ > + sample_type &= ~data->sample_flags; > + > if (sample_type & PERF_SAMPLE_TID) { > /* namespace issues */ > data->tid_entry.pid = perf_event_pid(event, current); > @@ -6820,6 +6826,8 @@ static void __perf_event_header__init_id(struct perf_event_header *header, > data->cpu_entry.cpu = raw_smp_processor_id(); > data->cpu_entry.reserved = 0; > } > + > + return sample_type; > } > > void perf_event_header__init_id(struct perf_event_header *header, > @@ -7302,7 +7310,7 @@ void perf_prepare_sample(struct perf_event_header *header, > struct perf_event *event, > struct pt_regs *regs) > { > - u64 sample_type = event->attr.sample_type; > + u64 sample_type; > > header->type = PERF_RECORD_SAMPLE; > header->size = sizeof(*header) + event->header_size; > @@ -7310,7 +7318,7 @@ void perf_prepare_sample(struct perf_event_header *header, > header->misc = 0; > header->misc |= perf_misc_flags(regs); > > - __perf_event_header__init_id(header, data, event); > + sample_type = __perf_event_header__init_id(header, data, event); > > if (sample_type & (PERF_SAMPLE_IP | PERF_SAMPLE_CODE_PAGE_SIZE)) > data->ip = perf_instruction_pointer(regs);
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