[PATCH 05/37] perf tools: Create separate mmap for dummy tracking event

[Namhyung Kim]

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@xxxxxxxxx>
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
 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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