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Subject[PATCH 2/2] perf tools: Make 'struct map_shared' truly shared
Date
Andi reported that maps cloning is eating lot of memory and
it's probably unnecessary, because they keep the same data.

Changing 'struct map_shared' to be a pointer inside 'struct map',
so it can be shared on fork. Changing the map__clone function to
actually share 'struct map_shared' for cloned maps.

The 'struct map_shared' carries its own refcnt counter, which is
incremented when it's assigned to new 'struct map' and decremented
when 'struct map' gets deleted in map__delete (its refcnt is 0).

This 'maps sharing' seems to save lot of heap for reports with
many forks/cloned mmaps (over 60% in example below).

Profile kernel build:

$ perf record make -j 40

Get heap profile (tools/perf directory):

$ <install gperftools>
$ make TCMALLOC=1
$ HEAPPROFILE=/tmp/heapprof ./perf report -i perf.data --stdio > out
$ pprof ./perf /tmp/heapprof.000*

Before:

(pprof) top
Total: 2335.5 MB
1735.1 74.3% 74.3% 1735.1 74.3% memdup
402.0 17.2% 91.5% 402.0 17.2% zalloc
140.2 6.0% 97.5% 145.8 6.2% map__new
33.6 1.4% 98.9% 33.6 1.4% symbol__new
12.4 0.5% 99.5% 12.4 0.5% alloc_event
6.2 0.3% 99.7% 6.2 0.3% nsinfo__new
5.5 0.2% 100.0% 5.5 0.2% nsinfo__copy
0.3 0.0% 100.0% 0.3 0.0% dso__new
0.1 0.0% 100.0% 0.1 0.0% do_read_string
0.0 0.0% 100.0% 0.0 0.0% __GI__IO_file_doallocate

After:

(pprof) top
Total: 758.5 MB
385.7 50.8% 50.8% 385.7 50.8% memdup
248.4 32.7% 83.6% 248.4 32.7% zalloc
91.2 12.0% 95.6% 94.8 12.5% map__new
19.3 2.5% 98.2% 19.3 2.5% symbol__new
6.2 0.8% 99.0% 6.2 0.8% alloc_event
3.9 0.5% 99.5% 3.9 0.5% nsinfo__new
3.5 0.5% 100.0% 3.5 0.5% nsinfo__copy
0.2 0.0% 100.0% 0.2 0.0% dso__new
0.0 0.0% 100.0% 0.0 0.0% do_read_string
0.0 0.0% 100.0% 0.0 0.0% elf_fill

The perf report output is the same.

Reported-by: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/n/tip-9x8utaeeqwyktzhruhrpp9g9@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/perf/util/map.c | 62 ++++++++++++++++++++++++++++++++--------
tools/perf/util/map.h | 7 +++--
tools/perf/util/symbol.c | 2 +-
3 files changed, 55 insertions(+), 16 deletions(-)

diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index 98c56714f1ae..9df18ef76241 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -145,6 +145,7 @@ void map__init(struct map *map, u64 start, u64 end, u64 pgoff, struct dso *dso)
map->groups = NULL;
sh->erange_warned = false;
refcount_set(&map->refcnt, 1);
+ refcount_set(&sh->refcnt, 1);
}

struct map *map__new(struct machine *machine, u64 start, u64 len,
@@ -153,14 +154,16 @@ struct map *map__new(struct machine *machine, u64 start, u64 len,
struct thread *thread)
{
struct map *map = malloc(sizeof(*map));
+ struct map_shared *sh = malloc(sizeof(*sh));
struct nsinfo *nsi = NULL;
struct nsinfo *nnsi;

- if (map != NULL) {
+ if (map != NULL && sh != NULL) {
char newfilename[PATH_MAX];
struct dso *dso;
int anon, no_dso, vdso, android;
- struct map_shared *sh = map_sh(map);
+
+ map->shared = sh;

android = is_android_lib(filename);
anon = is_anon_memory(filename, flags);
@@ -220,11 +223,12 @@ struct map *map__new(struct machine *machine, u64 start, u64 len,
}
dso->nsinfo = nsi;
dso__put(dso);
+ return map;
}
- return map;
out_delete:
nsinfo__put(nsi);
free(map);
+ free(sh);
return NULL;
}

@@ -235,13 +239,19 @@ struct map *map__new(struct machine *machine, u64 start, u64 len,
*/
struct map *map__new2(u64 start, struct dso *dso)
{
+ struct map_shared *sh = zalloc(sizeof(*sh));
struct map *map = calloc(1, (sizeof(*map) +
(dso->kernel ? sizeof(struct kmap) : 0)));
- if (map != NULL) {
+
+ if (map != NULL && sh != NULL) {
+ map->shared = sh;
/*
* ->end will be filled after we load all the symbols
*/
map__init(map, start, 0, 0, dso);
+ } else {
+ zfree(&map);
+ free(sh);
}

return map;
@@ -289,15 +299,29 @@ bool map__has_symbols(const struct map *map)
return dso__has_symbols(map_sh(map)->dso);
}

-static void map__exit(struct map *map)
+static void map_shared__delete(struct map_shared *sh)
{
- BUG_ON(!RB_EMPTY_NODE(&map->rb_node));
- dso__zput(map_sh(map)->dso);
+ dso__put(sh->dso);
+ free(sh);
+}
+
+static struct map_shared *map_shared__get(struct map_shared *sh)
+{
+ if (sh)
+ refcount_inc(&sh->refcnt);
+ return sh;
+}
+
+static void map_shared__put(struct map_shared *sh)
+{
+ if (sh && refcount_dec_and_test(&sh->refcnt))
+ map_shared__delete(sh);
}

void map__delete(struct map *map)
{
- map__exit(map);
+ BUG_ON(!RB_EMPTY_NODE(&map->rb_node));
+ map_shared__put(map->shared);
free(map);
}

@@ -390,12 +414,26 @@ struct symbol *map__find_symbol_by_name(struct map *map, const char *name)
return dso__find_symbol_by_name(map_sh(map)->dso, name);
}

-struct map *map__clone(struct map *from)
+struct map *map__clone(struct map *from, bool share)
{
struct map *map = memdup(from, sizeof(*map));
+ struct map_shared *sh;

if (map != NULL) {
refcount_set(&map->refcnt, 1);
+
+ if (share) {
+ sh = map_shared__get(map->shared);
+ } else {
+ sh = memdup(map->shared, sizeof(*sh));
+ if (!sh) {
+ free(map);
+ return NULL;
+ }
+ map->shared = sh;
+ refcount_set(&sh->refcnt, 1);
+ }
+
RB_CLEAR_NODE(&map->rb_node);
dso__get(map_sh(map)->dso);
map->groups = NULL;
@@ -840,7 +878,7 @@ static int maps__fixup_overlappings(struct maps *maps, struct map *map, FILE *fp
* overlapped by the new map:
*/
if (map_sh(map)->start > map_sh(pos)->start) {
- struct map *before = map__clone(pos);
+ struct map *before = map__clone(pos, false);

if (before == NULL) {
err = -ENOMEM;
@@ -855,7 +893,7 @@ static int maps__fixup_overlappings(struct maps *maps, struct map *map, FILE *fp
}

if (map_sh(map)->end < map_sh(pos)->end) {
- struct map *after = map__clone(pos);
+ struct map *after = map__clone(pos, false);

if (after == NULL) {
err = -ENOMEM;
@@ -902,7 +940,7 @@ int map_groups__clone(struct thread *thread, struct map_groups *parent)
down_read(&maps->lock);

for (map = maps__first(maps); map; map = map__next(map)) {
- struct map *new = map__clone(map);
+ struct map *new = map__clone(map, true);
if (new == NULL)
goto out_unlock;

diff --git a/tools/perf/util/map.h b/tools/perf/util/map.h
index 297e8f9d1c4c..2788894bdd1c 100644
--- a/tools/perf/util/map.h
+++ b/tools/perf/util/map.h
@@ -38,6 +38,7 @@ struct map_shared {
u64 (*unmap_ip)(struct map *, u64);

struct dso *dso;
+ refcount_t refcnt;
};

struct map {
@@ -46,12 +47,12 @@ struct map {
struct list_head node;
};
struct rb_node rb_node_name;
- struct map_shared shared;
+ struct map_shared *shared;
struct map_groups *groups;
refcount_t refcnt;
};

-#define map_sh(__m) (&((__m)->shared))
+#define map_sh(__m) ((__m)->shared)

struct kmap;

@@ -123,7 +124,7 @@ struct map *map__new(struct machine *machine, u64 start, u64 len,
char *filename, struct thread *thread);
struct map *map__new2(u64 start, struct dso *dso);
void map__delete(struct map *map);
-struct map *map__clone(struct map *map);
+struct map *map__clone(struct map *map, bool share);

static inline struct map *map__get(struct map *map)
{
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 80c4429304f0..bca6cbdd7eea 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1213,7 +1213,7 @@ int map_groups__merge_in(struct map_groups *kmaps, struct map *new_map)
* |new.............| -> |new..| |new..|
* |old....| -> |old....|
*/
- struct map *m = map__clone(new_map);
+ struct map *m = map__clone(new_map, false);

if (!m)
return -ENOMEM;
--
2.21.0
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