Re: [PATCH 12/15] perf tools: allow non-matching sample types

[Adrian Hunter <adrian.hunter@intel.com>]

On 25/06/13 14:23, Stephane Eranian wrote:
> On Mon, Jun 24, 2013 at 3:16 PM, Adrian Hunter <adrian.hunter@intel.com> wrote:
>> Sample types need not be identical to determine
>> the sample id from the event.  Only the position
>> of the sample id needs to be the same.
>>
>> Compatible sample types are ones in which the bits
>> defined by PERF_COMPAT_MASK are the same.
>> 'perf_evlist__config()' forces sample types to be
>> compatible on that basis.
>>
> This is indeed a major flaw of the current sampling buffer format.
> I have a patch coming to address this from the kernel side.
> 
> I am trying to understand this patch and I am confused by the
> description and especially the structure of COMPAT_MASK.
> 
> I agree that if the SAMPLE_ID position remains constant then
> it can be extracted from the body of the sample uniformly.
> The only way to guarantee a fixed position is by ensuring that
> all the sample_types before SAMPLE_ID and either set or
> unset. By before I don't mean in the enum order but in the
> order in which the kernel lays them various sample_types
> in the buffer. And that's determined by perf_output_sample().
> So I don't understand why PERF_SAMPLE_CPU and
> PERF_SAMPLE_STREAM_ID  are here.
> 
> Any explanation?

There are 2 sample formats: one for sample events and one for other events
(the id sample).  In perf tools refer __perf_evsel__parse_sample() vs
perf_evsel__parse_id_sample().


> 
> 
>> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
>> ---
>>  tools/perf/util/event.h  |  6 ++++
>>  tools/perf/util/evlist.c | 93 ++++++++++++++++++++++++++++++++++++++++++++++--
>>  tools/perf/util/evlist.h |  3 ++
>>  tools/perf/util/evsel.c  | 41 +++++++++++++++++++++
>>  tools/perf/util/evsel.h  |  4 +++
>>  5 files changed, 145 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
>> index 1813895..858572f 100644
>> --- a/tools/perf/util/event.h
>> +++ b/tools/perf/util/event.h
>> @@ -65,6 +65,12 @@ struct read_event {
>>         PERF_SAMPLE_ID | PERF_SAMPLE_STREAM_ID |        \
>>          PERF_SAMPLE_CPU | PERF_SAMPLE_PERIOD)
>>
>> +#define PERF_COMPAT_MASK                               \
>> +       (PERF_SAMPLE_IP   | PERF_SAMPLE_TID       |     \
>> +        PERF_SAMPLE_TIME | PERF_SAMPLE_ADDR      |     \
>> +        PERF_SAMPLE_ID   | PERF_SAMPLE_STREAM_ID |     \
>> +        PERF_SAMPLE_CPU)
>> +
>>  struct sample_event {
>>         struct perf_event_header        header;
>>         u64 array[];
>> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
>> index a660f56..85c4d91 100644
>> --- a/tools/perf/util/evlist.c
>> +++ b/tools/perf/util/evlist.c
>> @@ -49,10 +49,20 @@ struct perf_evlist *perf_evlist__new(void)
>>         return evlist;
>>  }
>>
>> +static void perf_evlist__set_id_pos(struct perf_evlist *evlist)
>> +{
>> +       struct perf_evsel *first = perf_evlist__first(evlist);
>> +
>> +       evlist->id_pos = first->id_pos;
>> +       evlist->is_pos = first->is_pos;
>> +}
>> +
>>  void perf_evlist__config(struct perf_evlist *evlist,
>>                         struct perf_record_opts *opts)
>>  {
>>         struct perf_evsel *evsel;
>> +       u64 compat = 0;
>> +
>>         /*
>>          * Set the evsel leader links before we configure attributes,
>>          * since some might depend on this info.
>> @@ -68,7 +78,15 @@ void perf_evlist__config(struct perf_evlist *evlist,
>>
>>                 if (evlist->nr_entries > 1)
>>                         perf_evsel__set_sample_id(evsel);
>> +               compat |= evsel->attr.sample_type & PERF_COMPAT_MASK;
>>         }
>> +
>> +       list_for_each_entry(evsel, &evlist->entries, node) {
>> +               evsel->attr.sample_type |= compat;
>> +               perf_evsel__calc_id_pos(evsel);
>> +       }
>> +
>> +       perf_evlist__set_id_pos(evlist);
>>  }
>>
>>  static void perf_evlist__purge(struct perf_evlist *evlist)
>> @@ -102,6 +120,7 @@ void perf_evlist__add(struct perf_evlist *evlist, struct perf_evsel *entry)
>>  {
>>         list_add_tail(&entry->node, &evlist->entries);
>>         ++evlist->nr_entries;
>> +       perf_evlist__set_id_pos(evlist);
>>  }
>>
>>  void perf_evlist__splice_list_tail(struct perf_evlist *evlist,
>> @@ -110,6 +129,7 @@ void perf_evlist__splice_list_tail(struct perf_evlist *evlist,
>>  {
>>         list_splice_tail(list, &evlist->entries);
>>         evlist->nr_entries += nr_entries;
>> +       perf_evlist__set_id_pos(evlist);
>>  }
>>
>>  void __perf_evlist__set_leader(struct list_head *list)
>> @@ -339,6 +359,55 @@ struct perf_evsel *perf_evlist__id2evsel(struct perf_evlist *evlist, u64 id)
>>         return NULL;
>>  }
>>
>> +static int perf_evlist__event2id(struct perf_evlist *evlist,
>> +                                union perf_event *event, u64 *id)
>> +{
>> +       const u64 *array = event->sample.array;
>> +       ssize_t n;
>> +
>> +       n = (event->header.size - sizeof(event->header)) >> 3;
>> +
>> +       if (event->header.type == PERF_RECORD_SAMPLE) {
>> +               if (evlist->id_pos >= n)
>> +                       return -1;
>> +               *id = array[evlist->id_pos];
>> +       } else {
>> +               if (evlist->is_pos >= n)
>> +                       return -1;
>> +               n -= evlist->is_pos;
>> +               *id = array[n];
>> +       }
>> +       return 0;
>> +}
>> +
>> +static struct perf_evsel *perf_evlist__event2evsel(struct perf_evlist *evlist,
>> +                                                  union perf_event *event)
>> +{
>> +       struct hlist_head *head;
>> +       struct perf_sample_id *sid;
>> +       int hash;
>> +       u64 id;
>> +
>> +       if (evlist->nr_entries == 1 || evlist->matching_sample_types)
>> +               return perf_evlist__first(evlist);
>> +
>> +       if (perf_evlist__event2id(evlist, event, &id))
>> +               return NULL;
>> +
>> +       /* Synthesized events have an id of zero */
>> +       if (!id)
>> +               return perf_evlist__first(evlist);
>> +
>> +       hash = hash_64(id, PERF_EVLIST__HLIST_BITS);
>> +       head = &evlist->heads[hash];
>> +
>> +       hlist_for_each_entry(sid, head, node) {
>> +               if (sid->id == id)
>> +                       return sid->evsel;
>> +       }
>> +       return NULL;
>> +}
>> +
>>  union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
>>  {
>>         struct perf_mmap *md = &evlist->mmap[idx];
>> @@ -650,9 +719,26 @@ int perf_evlist__set_filter(struct perf_evlist *evlist, const char *filter)
>>  bool perf_evlist__valid_sample_type(struct perf_evlist *evlist)
>>  {
>>         struct perf_evsel *first = perf_evlist__first(evlist), *pos = first;
>> +       bool ok = true;
>>
>>         list_for_each_entry_continue(pos, &evlist->entries, node) {
>> -               if (first->attr.sample_type != pos->attr.sample_type)
>> +               if (first->attr.sample_type != pos->attr.sample_type) {
>> +                       ok = false;
>> +                       break;
>> +               }
>> +       }
>> +
>> +       if (ok) {
>> +               evlist->matching_sample_types = true;
>> +               return true;
>> +       }
>> +
>> +       if (evlist->id_pos < 0 || evlist->is_pos < 0)
>> +               return false;
>> +
>> +       list_for_each_entry(pos, &evlist->entries, node) {
>> +               if (pos->id_pos != evlist->id_pos ||
>> +                   pos->is_pos != evlist->is_pos)
>>                         return false;
>>         }
>>
>> @@ -848,7 +934,10 @@ int perf_evlist__start_workload(struct perf_evlist *evlist)
>>  int perf_evlist__parse_sample(struct perf_evlist *evlist, union perf_event *event,
>>                               struct perf_sample *sample)
>>  {
>> -       struct perf_evsel *evsel = perf_evlist__first(evlist);
>> +       struct perf_evsel *evsel = perf_evlist__event2evsel(evlist, event);
>> +
>> +       if (!evsel)
>> +               return -EFAULT;
>>         return perf_evsel__parse_sample(evsel, event, sample);
>>  }
>>
>> diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
>> index 0583d36..bfcbf67 100644
>> --- a/tools/perf/util/evlist.h
>> +++ b/tools/perf/util/evlist.h
>> @@ -32,11 +32,14 @@ struct perf_evlist {
>>         int              nr_fds;
>>         int              nr_mmaps;
>>         int              mmap_len;
>> +       int              id_pos;
>> +       int              is_pos;
>>         struct {
>>                 int     cork_fd;
>>                 pid_t   pid;
>>         } workload;
>>         bool             overwrite;
>> +       bool             matching_sample_types;
>>         struct perf_mmap *mmap;
>>         struct pollfd    *pollfd;
>>         struct thread_map *threads;
>> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
>> index d01d2cd..ee0f894 100644
>> --- a/tools/perf/util/evsel.c
>> +++ b/tools/perf/util/evsel.c
>> @@ -46,6 +46,46 @@ static int __perf_evsel__sample_size(u64 sample_type)
>>         return size;
>>  }
>>
>> +static int __perf_evsel__calc_id_pos(u64 sample_type)
>> +{
>> +       u64 mask;
>> +       int i, idx;
>> +
>> +       if (!(sample_type & PERF_SAMPLE_ID))
>> +               return -1;
>> +
>> +       mask = sample_type & (PERF_SAMPLE_ID - 1);
>> +
>> +       for (i = 0, idx = 0; i < 64; i++) {
>> +               if (mask & (1ULL << i))
>> +                       idx++;
>> +       }
>> +
>> +       return idx;
>> +}
>> +
>> +static int __perf_evsel__calc_is_pos(u64 sample_type)
>> +{
>> +       int idx = 1;
>> +
>> +       if (!(sample_type & PERF_SAMPLE_ID))
>> +               return -1;
>> +
>> +       if (sample_type & PERF_SAMPLE_CPU)
>> +               idx += 1;
>> +
>> +       if (sample_type & PERF_SAMPLE_STREAM_ID)
>> +               idx += 1;
>> +
>> +       return idx;
>> +}
>> +
>> +void perf_evsel__calc_id_pos(struct perf_evsel *evsel)
>> +{
>> +       evsel->id_pos = __perf_evsel__calc_id_pos(evsel->attr.sample_type);
>> +       evsel->is_pos = __perf_evsel__calc_is_pos(evsel->attr.sample_type);
>> +}
>> +
>>  void hists__init(struct hists *hists)
>>  {
>>         memset(hists, 0, sizeof(*hists));
>> @@ -89,6 +129,7 @@ void perf_evsel__init(struct perf_evsel *evsel,
>>         INIT_LIST_HEAD(&evsel->node);
>>         hists__init(&evsel->hists);
>>         evsel->sample_size = __perf_evsel__sample_size(attr->sample_type);
>> +       perf_evsel__calc_id_pos(evsel);
>>  }
>>
>>  struct perf_evsel *perf_evsel__new(struct perf_event_attr *attr, int idx)
>> diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
>> index 3f156cc..88b4319 100644
>> --- a/tools/perf/util/evsel.h
>> +++ b/tools/perf/util/evsel.h
>> @@ -71,6 +71,8 @@ struct perf_evsel {
>>         } handler;
>>         struct cpu_map          *cpus;
>>         unsigned int            sample_size;
>> +       int                     id_pos;
>> +       int                     is_pos;
>>         bool                    supported;
>>         bool                    needs_swap;
>>         /* parse modifier helper */
>> @@ -100,6 +102,8 @@ void perf_evsel__delete(struct perf_evsel *evsel);
>>  void perf_evsel__config(struct perf_evsel *evsel,
>>                         struct perf_record_opts *opts);
>>
>> +void perf_evsel__calc_id_pos(struct perf_evsel *evsel);
>> +
>>  bool perf_evsel__is_cache_op_valid(u8 type, u8 op);
>>
>>  #define PERF_EVSEL__MAX_ALIASES 8
>> --
>> 1.7.11.7
>>
> 
>