[PATCH v15 2/8] perf evlist: Introduce aux evlist

[Wang Nan]

An auxiliary evlist is created by perf_evlist__new_aux() using an
existing evlist as its parent. An auxiliary evlist can have its own
'struct perf_mmap', but can't have any other data. User should use its
parent instead when accessing other data.

Auxiliary evlists are containers of 'struct perf_mmap'. It is introduced
to allow its parent evlist to map different events into separated mmaps.

Following commits create an auxiliary evlist for overwritable
events, because overwritable events need a read only and backwards ring
buffer, which is different from normal events.

To achieve this goal, this patch carefully changes 'evlist' to
'evlist->parent' in all functions in the path of 'perf_evlist__mmap_ex',
except 'evlist->mmap' related operations, to make sure all evlist
modifications (like pollfd and event id hash tables) goes to original
evlist.

A 'evlist->parent' pointer is added to 'struct perf_evlist' and points to
the evlist itself for normal evlists.

Children of one evlist are linked into it so one can find all children
from its parent.

To avoid potential complexity, forbid creating aux evlist from another
aux evlist.

Improve perf_evlist__munmap_filtered(), so when recording, if an event
is terminated, unmap mmaps, from parent and children.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: He Kuang <hekuang@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Zefan Li <lizefan@xxxxxxxxxx>
Cc: Nilay Vaish <nilayvaish@xxxxxxxxx>
Cc: pi3orama@xxxxxxx
---
 tools/perf/util/evlist.c | 49 +++++++++++++++++++++++++++++++++++++-----------
 tools/perf/util/evlist.h | 12 ++++++++++++
 2 files changed, 50 insertions(+), 11 deletions(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 7228596..7000fe2 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -41,10 +41,12 @@ void perf_evlist__init(struct perf_evlist *evlist, struct cpu_map *cpus,
 	for (i = 0; i < PERF_EVLIST__HLIST_SIZE; ++i)
 		INIT_HLIST_HEAD(&evlist->heads[i]);
 	INIT_LIST_HEAD(&evlist->entries);
+	INIT_LIST_HEAD(&evlist->children);
 	perf_evlist__set_maps(evlist, cpus, threads);
 	fdarray__init(&evlist->pollfd, 64);
 	evlist->workload.pid = -1;
 	evlist->backward = false;
+	evlist->parent = evlist;
 }
 
 struct perf_evlist *perf_evlist__new(void)
@@ -490,13 +492,17 @@ static void perf_evlist__munmap_filtered(struct fdarray *fda, int fd,
 					 void *arg __maybe_unused)
 {
 	struct perf_evlist *evlist = container_of(fda, struct perf_evlist, pollfd);
+	struct perf_evlist *child;
 
 	perf_evlist__mmap_put(evlist, fda->priv[fd].idx);
+	list_for_each_entry(child, &evlist->children, list)
+		perf_evlist__mmap_put(child, fda->priv[fd].idx);
+
 }
 
 int perf_evlist__filter_pollfd(struct perf_evlist *evlist, short revents_and_mask)
 {
-	return fdarray__filter(&evlist->pollfd, revents_and_mask,
+	return fdarray__filter(&evlist->parent->pollfd, revents_and_mask,
 			       perf_evlist__munmap_filtered, NULL);
 }
 
@@ -1015,7 +1021,7 @@ static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx,
 	struct perf_evsel *evsel;
 	int revent;
 
-	evlist__for_each_entry(evlist, evsel) {
+	evlist__for_each_entry(evlist->parent, evsel) {
 		int fd;
 
 		if (!!evsel->attr.write_backward != (evlist->overwrite && evlist->backward))
@@ -1047,16 +1053,16 @@ static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx,
 		 * Therefore don't add it for polling.
 		 */
 		if (!evsel->system_wide &&
-		    __perf_evlist__add_pollfd(evlist, fd, idx, revent) < 0) {
+		    __perf_evlist__add_pollfd(evlist->parent, fd, idx, revent) < 0) {
 			perf_evlist__mmap_put(evlist, idx);
 			return -1;
 		}
 
 		if (evsel->attr.read_format & PERF_FORMAT_ID) {
-			if (perf_evlist__id_add_fd(evlist, evsel, cpu, thread,
+			if (perf_evlist__id_add_fd(evlist->parent, evsel, cpu, thread,
 						   fd) < 0)
 				return -1;
-			perf_evlist__set_sid_idx(evlist, evsel, idx, cpu,
+			perf_evlist__set_sid_idx(evlist->parent, evsel, idx, cpu,
 						 thread);
 		}
 	}
@@ -1097,13 +1103,13 @@ static int perf_evlist__mmap_per_thread(struct perf_evlist *evlist,
 					struct mmap_params *mp)
 {
 	int thread;
-	int nr_threads = thread_map__nr(evlist->threads);
+	int nr_threads = thread_map__nr(evlist->parent->threads);
 
 	pr_debug2("perf event ring buffer mmapped per thread\n");
 	for (thread = 0; thread < nr_threads; thread++) {
 		int output = -1;
 
-		auxtrace_mmap_params__set_idx(&mp->auxtrace_mp, evlist, thread,
+		auxtrace_mmap_params__set_idx(&mp->auxtrace_mp, evlist->parent, thread,
 					      false);
 
 		if (perf_evlist__mmap_per_evsel(evlist, thread, mp, 0, thread,
@@ -1242,8 +1248,8 @@ int perf_evlist__mmap_ex(struct perf_evlist *evlist, unsigned int pages,
 			 bool auxtrace_overwrite)
 {
 	struct perf_evsel *evsel;
-	const struct cpu_map *cpus = evlist->cpus;
-	const struct thread_map *threads = evlist->threads;
+	const struct cpu_map *cpus = evlist->parent->cpus;
+	const struct thread_map *threads = evlist->parent->threads;
 	struct mmap_params mp = {
 		.prot = PROT_READ | (overwrite ? 0 : PROT_WRITE),
 	};
@@ -1251,7 +1257,7 @@ int perf_evlist__mmap_ex(struct perf_evlist *evlist, unsigned int pages,
 	if (evlist->mmap == NULL && perf_evlist__alloc_mmap(evlist) < 0)
 		return -ENOMEM;
 
-	if (evlist->pollfd.entries == NULL && perf_evlist__alloc_pollfd(evlist) < 0)
+	if (evlist->parent->pollfd.entries == NULL && perf_evlist__alloc_pollfd(evlist->parent) < 0)
 		return -ENOMEM;
 
 	evlist->overwrite = overwrite;
@@ -1262,7 +1268,7 @@ int perf_evlist__mmap_ex(struct perf_evlist *evlist, unsigned int pages,
 	auxtrace_mmap_params__init(&mp.auxtrace_mp, evlist->mmap_len,
 				   auxtrace_pages, auxtrace_overwrite);
 
-	evlist__for_each_entry(evlist, evsel) {
+	evlist__for_each_entry(evlist->parent, evsel) {
 		if ((evsel->attr.read_format & PERF_FORMAT_ID) &&
 		    evsel->sample_id == NULL &&
 		    perf_evsel__alloc_id(evsel, cpu_map__nr(cpus), threads->nr) < 0)
@@ -1919,3 +1925,24 @@ perf_evlist__find_evsel_by_str(struct perf_evlist *evlist,
 
 	return NULL;
 }
+
+struct perf_evlist *perf_evlist__new_aux(struct perf_evlist *parent)
+{
+	struct perf_evlist *evlist;
+
+	if (perf_evlist__is_aux(parent)) {
+		pr_err("Internal error: create aux evlist from another aux evlist\n");
+		return NULL;
+	}
+
+	evlist = zalloc(sizeof(*evlist));
+	if (!evlist)
+		return NULL;
+
+	perf_evlist__init(evlist, parent->cpus, parent->threads);
+	evlist->parent = parent;
+	INIT_LIST_HEAD(&evlist->list);
+	list_add(&evlist->list, &parent->children);
+
+	return evlist;
+}
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 872912b..99bcc02 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -37,6 +37,10 @@ struct perf_mmap {
 
 struct perf_evlist {
 	struct list_head entries;
+	union {
+		struct list_head children;
+		struct list_head list;
+	};
 	struct hlist_head heads[PERF_EVLIST__HLIST_SIZE];
 	int		 nr_entries;
 	int		 nr_groups;
@@ -60,8 +64,14 @@ struct perf_evlist {
 	struct perf_evsel *selected;
 	struct events_stats stats;
 	struct perf_env	*env;
+	struct perf_evlist *parent;
 };
 
+static inline bool perf_evlist__is_aux(struct perf_evlist *evlist)
+{
+	return evlist->parent != evlist;
+}
+
 struct perf_evsel_str_handler {
 	const char *name;
 	void	   *handler;
@@ -70,6 +80,8 @@ struct perf_evsel_str_handler {
 struct perf_evlist *perf_evlist__new(void);
 struct perf_evlist *perf_evlist__new_default(void);
 struct perf_evlist *perf_evlist__new_dummy(void);
+struct perf_evlist *perf_evlist__new_aux(struct perf_evlist *);
+
 void perf_evlist__init(struct perf_evlist *evlist, struct cpu_map *cpus,
 		       struct thread_map *threads);
 void perf_evlist__exit(struct perf_evlist *evlist);
-- 
1.8.3.4