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Subject[PATCH 05/37] perf tools: Create separate mmap for dummy tracking event
Date
When multi file support is enabled, a dummy tracking event will be
used to track metadata (like task, comm and mmap events) for a session
and actual samples will be recorded in separate files.

Provide separate mmap to the dummy tracking event. The size is fixed
to 128KiB (+ 1 page) as the event rate will be lower than samples. I
originally wanted to use a single mmap for this but cross-cpu sharing
is prohibited so it's per-cpu (or per-task) like normal mmaps.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
tools/perf/builtin-record.c | 9 +++-
tools/perf/util/evlist.c | 104 +++++++++++++++++++++++++++++++++++---------
tools/perf/util/evlist.h | 11 ++++-
3 files changed, 102 insertions(+), 22 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 054c6e57d3b9..129fab35fdc5 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -69,7 +69,7 @@ static int process_synthesized_event(struct perf_tool *tool,

static int record__mmap_read(struct record *rec, int idx)
{
- struct perf_mmap *md = &rec->evlist->mmap[idx];
+ struct perf_mmap *md = perf_evlist__mmap_desc(rec->evlist, idx);
unsigned int head = perf_mmap__read_head(md);
unsigned int old = md->prev;
unsigned char *data = md->base + page_size;
@@ -105,6 +105,7 @@ static int record__mmap_read(struct record *rec, int idx)
}

md->prev = old;
+
perf_evlist__mmap_consume(rec->evlist, idx);
out:
return rc;
@@ -263,6 +264,12 @@ static int record__mmap_read_all(struct record *rec)
goto out;
}
}
+ if (rec->evlist->track_mmap) {
+ if (record__mmap_read(rec, track_mmap_idx(i)) != 0) {
+ rc = -1;
+ goto out;
+ }
+ }
}

/*
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 72dff295237e..d99343b988fe 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -27,6 +27,7 @@

static void perf_evlist__mmap_put(struct perf_evlist *evlist, int idx);
static void __perf_evlist__munmap(struct perf_evlist *evlist, int idx);
+static void __perf_evlist__munmap_track(struct perf_evlist *evlist, int idx);

#define FD(e, x, y) (*(int *)xyarray__entry(e->fd, x, y))
#define SID(e, x, y) xyarray__entry(e->sample_id, x, y)
@@ -735,22 +736,39 @@ static bool perf_mmap__empty(struct perf_mmap *md)
return perf_mmap__read_head(md) != md->prev;
}

+struct perf_mmap *perf_evlist__mmap_desc(struct perf_evlist *evlist, int idx)
+{
+ if (idx >= 0)
+ return &evlist->mmap[idx];
+ else
+ return &evlist->track_mmap[track_mmap_idx(idx)];
+}
+
static void perf_evlist__mmap_get(struct perf_evlist *evlist, int idx)
{
- ++evlist->mmap[idx].refcnt;
+ struct perf_mmap *md = perf_evlist__mmap_desc(evlist, idx);
+
+ ++md->refcnt;
}

static void perf_evlist__mmap_put(struct perf_evlist *evlist, int idx)
{
- BUG_ON(evlist->mmap[idx].refcnt == 0);
+ struct perf_mmap *md = perf_evlist__mmap_desc(evlist, idx);
+
+ BUG_ON(md->refcnt == 0);
+
+ if (--md->refcnt != 0)
+ return;

- if (--evlist->mmap[idx].refcnt == 0)
+ if (idx >= 0)
__perf_evlist__munmap(evlist, idx);
+ else
+ __perf_evlist__munmap_track(evlist, track_mmap_idx(idx));
}

void perf_evlist__mmap_consume(struct perf_evlist *evlist, int idx)
{
- struct perf_mmap *md = &evlist->mmap[idx];
+ struct perf_mmap *md = perf_evlist__mmap_desc(evlist, idx);

if (!evlist->overwrite) {
unsigned int old = md->prev;
@@ -771,6 +789,15 @@ static void __perf_evlist__munmap(struct perf_evlist *evlist, int idx)
}
}

+static void __perf_evlist__munmap_track(struct perf_evlist *evlist, int idx)
+{
+ if (evlist->track_mmap[idx].base != NULL) {
+ munmap(evlist->track_mmap[idx].base, TRACK_MMAP_SIZE);
+ evlist->track_mmap[idx].base = NULL;
+ evlist->track_mmap[idx].refcnt = 0;
+ }
+}
+
void perf_evlist__munmap(struct perf_evlist *evlist)
{
int i;
@@ -782,23 +809,43 @@ void perf_evlist__munmap(struct perf_evlist *evlist)
__perf_evlist__munmap(evlist, i);

zfree(&evlist->mmap);
+
+ if (evlist->track_mmap == NULL)
+ return;
+
+ for (i = 0; i < evlist->nr_mmaps; i++)
+ __perf_evlist__munmap_track(evlist, i);
+
+ zfree(&evlist->track_mmap);
}

-static int perf_evlist__alloc_mmap(struct perf_evlist *evlist)
+static int perf_evlist__alloc_mmap(struct perf_evlist *evlist, bool track_mmap)
{
evlist->nr_mmaps = cpu_map__nr(evlist->cpus);
if (cpu_map__empty(evlist->cpus))
evlist->nr_mmaps = thread_map__nr(evlist->threads);
evlist->mmap = zalloc(evlist->nr_mmaps * sizeof(struct perf_mmap));
- return evlist->mmap != NULL ? 0 : -ENOMEM;
+ if (evlist->mmap == NULL)
+ return -ENOMEM;
+
+ if (track_mmap) {
+ evlist->track_mmap = calloc(evlist->nr_mmaps,
+ sizeof(struct perf_mmap));
+ if (evlist->track_mmap == NULL) {
+ zfree(&evlist->mmap);
+ return -ENOMEM;
+ }
+ }
+ return 0;
}

struct mmap_params {
- int prot;
- int mask;
+ int prot;
+ size_t len;
};

-static int __perf_evlist__mmap(struct perf_evlist *evlist, int idx,
+static int __perf_evlist__mmap(struct perf_evlist *evlist __maybe_unused,
+ struct perf_mmap *pmmap,
struct mmap_params *mp, int fd)
{
/*
@@ -814,15 +861,14 @@ static int __perf_evlist__mmap(struct perf_evlist *evlist, int idx,
* evlist layer can't just drop it when filtering events in
* perf_evlist__filter_pollfd().
*/
- evlist->mmap[idx].refcnt = 2;
- evlist->mmap[idx].prev = 0;
- evlist->mmap[idx].mask = mp->mask;
- evlist->mmap[idx].base = mmap(NULL, evlist->mmap_len, mp->prot,
- MAP_SHARED, fd, 0);
- if (evlist->mmap[idx].base == MAP_FAILED) {
+ pmmap->refcnt = 2;
+ pmmap->prev = 0;
+ pmmap->mask = mp->len - page_size - 1;
+ pmmap->base = mmap(NULL, mp->len, mp->prot, MAP_SHARED, fd, 0);
+ if (pmmap->base == MAP_FAILED) {
pr_debug2("failed to mmap perf event ring buffer, error %d\n",
errno);
- evlist->mmap[idx].base = NULL;
+ pmmap->base = NULL;
return -1;
}

@@ -843,9 +889,22 @@ static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx,

fd = FD(evsel, cpu, thread);

- if (*output == -1) {
+ if (perf_evsel__is_dummy_tracking(evsel)) {
+ struct mmap_params track_mp = {
+ .prot = mp->prot,
+ .len = TRACK_MMAP_SIZE,
+ };
+
+ if (__perf_evlist__mmap(evlist, &evlist->track_mmap[idx],
+ &track_mp, fd) < 0)
+ return -1;
+
+ /* mark idx as track mmap idx (negative) */
+ idx = track_mmap_idx(idx);
+ } else if (*output == -1) {
*output = fd;
- if (__perf_evlist__mmap(evlist, idx, mp, *output) < 0)
+ if (__perf_evlist__mmap(evlist, &evlist->mmap[idx],
+ mp, *output) < 0)
return -1;
} else {
if (ioctl(fd, PERF_EVENT_IOC_SET_OUTPUT, *output) != 0)
@@ -874,6 +933,11 @@ static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx,
perf_evlist__set_sid_idx(evlist, evsel, idx, cpu,
thread);
}
+
+ if (mp->track && perf_evsel__is_dummy_tracking(evsel)) {
+ /* restore idx as normal idx (positive) */
+ idx = track_mmap_idx(idx);
+ }
}

return 0;
@@ -1025,7 +1089,7 @@ int perf_evlist__mmap(struct perf_evlist *evlist, unsigned int pages,
.prot = PROT_READ | (overwrite ? 0 : PROT_WRITE),
};

- if (evlist->mmap == NULL && perf_evlist__alloc_mmap(evlist) < 0)
+ if (evlist->mmap == NULL && perf_evlist__alloc_mmap(evlist, use_track_mmap) < 0)
return -ENOMEM;

if (evlist->pollfd.entries == NULL && perf_evlist__alloc_pollfd(evlist) < 0)
@@ -1034,7 +1098,7 @@ int perf_evlist__mmap(struct perf_evlist *evlist, unsigned int pages,
evlist->overwrite = overwrite;
evlist->mmap_len = perf_evlist__mmap_size(pages);
pr_debug("mmap size %zuB\n", evlist->mmap_len);
- mp.mask = evlist->mmap_len - page_size - 1;
+ mp.len = evlist->mmap_len;

evlist__for_each(evlist, evsel) {
if ((evsel->attr.read_format & PERF_FORMAT_ID) &&
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index b974bddf6b8b..b7f54b8577f7 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -48,11 +48,14 @@ struct perf_evlist {
bool overwrite;
struct fdarray pollfd;
struct perf_mmap *mmap;
+ struct perf_mmap *track_mmap;
struct thread_map *threads;
struct cpu_map *cpus;
struct perf_evsel *selected;
};

+#define TRACK_MMAP_SIZE (((128 * 1024 / page_size) + 1) * page_size)
+
struct perf_evsel_str_handler {
const char *name;
void *handler;
@@ -100,8 +103,8 @@ struct perf_evsel *perf_evlist__id2evsel(struct perf_evlist *evlist, u64 id);
struct perf_sample_id *perf_evlist__id2sid(struct perf_evlist *evlist, u64 id);

union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx);
-
void perf_evlist__mmap_consume(struct perf_evlist *evlist, int idx);
+struct perf_mmap *perf_evlist__mmap_desc(struct perf_evlist *evlist, int idx);

int perf_evlist__open(struct perf_evlist *evlist);
void perf_evlist__close(struct perf_evlist *evlist);
@@ -211,6 +214,12 @@ bool perf_evlist__can_select_event(struct perf_evlist *evlist, const char *str);
void perf_evlist__to_front(struct perf_evlist *evlist,
struct perf_evsel *move_evsel);

+/* convert from/to negative idx for track mmaps */
+static inline int track_mmap_idx(int idx)
+{
+ return -idx - 1;
+}
+
/**
* __evlist__for_each - iterate thru all the evsels
* @list: list_head instance to iterate
--
2.1.3


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