[PATCH v3 18/20] perf session: Add dso__session() and session-scoped allocation wrappers

[Ian Rogers]

Add explicit session-scoped memory allocation wrappers:
- perf_session__malloc(session, size)
- perf_session__zalloc(session, size)
- perf_session__calloc(session, nmemb, size)
- perf_session__realloc(session, ptr, size)
- perf_session__strdup(session, s)

When an allocation fails and returns NULL, if a non-NULL struct
perf_session is provided, the wrapper invokes perf_session__shrink() to
evict unreferenced symbols, DSOs, and cached debuginfo across the
session's machines and then retries the allocation once. This avoids
the thrashing overhead of periodic heuristic shrinking while allowing
perf to recover from memory exhaustion.

Also plumb a back-pointer from struct dsos to its owning struct machine
so machine__session(machine) and dso__session(dso) can resolve the
active perf_session.

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/perf/util/dso.c     |  7 ++++
 tools/perf/util/dso.h     |  2 ++
 tools/perf/util/dsos.c    |  1 +
 tools/perf/util/dsos.h    |  1 +
 tools/perf/util/machine.c |  1 +
 tools/perf/util/machine.h |  5 +++
 tools/perf/util/session.c | 70 +++++++++++++++++++++++++++++++++++++++
 tools/perf/util/session.h |  6 ++++
 8 files changed, 93 insertions(+)

diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 184d49935bfd..7b71fd5e48a9 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -1907,6 +1907,13 @@ void dso__delete(struct dso *dso)
 	RC_CHK_FREE(dso);
 }
 
+struct perf_session *dso__session(const struct dso *dso)
+{
+	struct dsos *dsos = dso ? RC_CHK_ACCESS(dso)->dsos : NULL;
+
+	return dsos ? machine__session(dsos->machine) : NULL;
+}
+
 bool dso__can_shrink_symbols(const struct dso *dso)
 {
 	const char *name;
diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index 7f217815ec07..9b01a86526c1 100644
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -20,6 +20,7 @@
 struct machine;
 struct map;
 struct perf_env;
+struct perf_session;
 
 #define DSO__NAME_KALLSYMS	"[kernel.kallsyms]"
 #define DSO__NAME_KCORE		"[kernel.kcore]"
@@ -791,6 +792,7 @@ static inline refcount_t *dso__refcnt(struct dso *dso)
 
 bool dso__can_shrink_symbols(const struct dso *dso);
 size_t dso__shrink(struct dso *dso);
+struct perf_session *dso__session(const struct dso *dso);
 
 char *dso__filename_with_chroot(const struct dso *dso, const char *filename);
 
diff --git a/tools/perf/util/dsos.c b/tools/perf/util/dsos.c
index f6868ffcc3e1..d53a8ab217e6 100644
--- a/tools/perf/util/dsos.c
+++ b/tools/perf/util/dsos.c
@@ -18,6 +18,7 @@ void dsos__init(struct dsos *dsos)
 {
 	init_rwsem(&dsos->lock);
 
+	dsos->machine = NULL;
 	dsos->cnt = 0;
 	dsos->allocated = 0;
 	dsos->dsos = NULL;
diff --git a/tools/perf/util/dsos.h b/tools/perf/util/dsos.h
index 151efdba2aa4..d636e4c5cbaf 100644
--- a/tools/perf/util/dsos.h
+++ b/tools/perf/util/dsos.h
@@ -19,6 +19,7 @@ struct machine;
  */
 struct dsos {
 	struct rw_semaphore lock;
+	struct machine *machine;
 	struct dso **dsos;
 	unsigned int cnt;
 	unsigned int allocated;
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index dad06eb865e6..c89f47ba16f2 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -81,6 +81,7 @@ int machine__init(struct machine *machine, const char *root_dir, pid_t pid)
 	memset(machine, 0, sizeof(*machine));
 	RB_CLEAR_NODE(&machine->rb_node);
 	dsos__init(&machine->dsos);
+	machine->dsos.machine = machine;
 	threads__init(&machine->threads);
 
 	machine->kmaps = maps__new(machine);
diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
index 0f4c0ae5b56d..6192bd3e33bb 100644
--- a/tools/perf/util/machine.h
+++ b/tools/perf/util/machine.h
@@ -164,6 +164,11 @@ static inline struct perf_session *machines__session(struct machines *machines)
 	return machines->session;
 }
 
+static inline struct perf_session *machine__session(const struct machine *machine)
+{
+	return machine && machine->machines ? machine->machines->session : NULL;
+}
+
 void machines__process_guests(struct machines *machines,
 			      machine__process_t process, void *data);
 
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 3f35c7affc29..3d4bc9c0063a 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -4274,3 +4274,73 @@ size_t perf_session__shrink(struct perf_session *session)
 
 	return machines__shrink(&session->machines);
 }
+
+static __thread bool perf_session__in_shrink;
+
+static bool perf_session__try_shrink(struct perf_session *session)
+{
+	size_t freed;
+
+	if (!session || perf_session__in_shrink)
+		return false;
+
+	perf_session__in_shrink = true;
+	freed = perf_session__shrink(session);
+	perf_session__in_shrink = false;
+
+	return freed > 0;
+}
+
+void *perf_session__malloc(struct perf_session *session, size_t size)
+{
+	void *ptr = malloc(size);
+
+	if (unlikely(!ptr && size != 0) && perf_session__try_shrink(session))
+		ptr = malloc(size);
+
+	return ptr;
+}
+
+void *perf_session__zalloc(struct perf_session *session, size_t size)
+{
+	void *ptr = zalloc(size);
+
+	if (unlikely(!ptr && size != 0) && perf_session__try_shrink(session))
+		ptr = zalloc(size);
+
+	return ptr;
+}
+
+void *perf_session__calloc(struct perf_session *session, size_t nmemb, size_t size)
+{
+	void *ptr = calloc(nmemb, size);
+
+	if (unlikely(!ptr && nmemb != 0 && size != 0) && perf_session__try_shrink(session))
+		ptr = calloc(nmemb, size);
+
+	return ptr;
+}
+
+void *perf_session__realloc(struct perf_session *session, void *ptr, size_t size)
+{
+	void *new_ptr = realloc(ptr, size);
+
+	if (unlikely(!new_ptr && size != 0) && perf_session__try_shrink(session))
+		new_ptr = realloc(ptr, size);
+
+	return new_ptr;
+}
+
+char *perf_session__strdup(struct perf_session *session, const char *s)
+{
+	char *dup;
+
+	if (!s)
+		return NULL;
+
+	dup = strdup(s);
+	if (unlikely(!dup) && perf_session__try_shrink(session))
+		dup = strdup(s);
+
+	return dup;
+}
diff --git a/tools/perf/util/session.h b/tools/perf/util/session.h
index cbea6792a008..c6157eddcc43 100644
--- a/tools/perf/util/session.h
+++ b/tools/perf/util/session.h
@@ -213,4 +213,10 @@ uint16_t perf_session__e_machine(struct perf_session *session, uint32_t *e_flags
 
 size_t perf_session__shrink(struct perf_session *session);
 
+void *perf_session__malloc(struct perf_session *session, size_t size);
+void *perf_session__zalloc(struct perf_session *session, size_t size);
+void *perf_session__calloc(struct perf_session *session, size_t nmemb, size_t size);
+void *perf_session__realloc(struct perf_session *session, void *ptr, size_t size);
+char *perf_session__strdup(struct perf_session *session, const char *s);
+
 #endif /* __PERF_SESSION_H */
-- 
2.56.0.542.g3ef89b7020-goog