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Message-ID: <CABPqkBRoRgHUM5ahHmvYXJ1BkHncm9Z2GZkzuRFbsNfh4=HJ6g@mail.gmail.com>
Date: Tue, 25 Jun 2013 13:23:36 +0200
From: Stephane Eranian <eranian@...gle.com>
To: Adrian Hunter <adrian.hunter@...el.com>
Cc: Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
LKML <linux-kernel@...r.kernel.org>,
David Ahern <dsahern@...il.com>,
Frederic Weisbecker <fweisbec@...il.com>,
Jiri Olsa <jolsa@...hat.com>, Mike Galbraith <efault@....de>,
Namhyung Kim <namhyung@...il.com>,
Paul Mackerras <paulus@...ba.org>,
Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 12/15] perf tools: allow non-matching sample types
On Mon, Jun 24, 2013 at 3:16 PM, Adrian Hunter <adrian.hunter@...el.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?
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.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
>
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