[tip:perf/core] perf tools: Reference count struct dso

From: tip-bot for Arnaldo Carvalho de Melo
Date: Tue Jun 09 2015 - 05:58:01 EST

Commit-ID: d3a7c489c7fd2463e3b2c3a2179c7be879dd9cb4
Gitweb: http://git.kernel.org/tip/d3a7c489c7fd2463e3b2c3a2179c7be879dd9cb4
Author: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
AuthorDate: Tue, 2 Jun 2015 11:53:26 -0300
Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Mon, 8 Jun 2015 10:31:40 -0300

perf tools: Reference count struct dso

This has a different model than the 'thread' and 'map' struct lifetimes:
there is not a definitive "don't use this DSO anymore" event, i.e. we may
get many 'struct map' holding references to the '/usr/lib64/libc-2.20.so'
DSO but then at some point some DSO may have no references but we still
don't want to straight away release its resources, because "soon" we may
get a new 'struct map' that needs it and we want to reuse its symtab or
other resources.

So we need some way to garbage collect it when crossing some memory
usage threshold, which is left for anoter patch, for now it is
sufficient to release it when calling dsos__exit(), i.e. when deleting
the whole list as part of deleting the 'struct machine' containing it,
which will leave only referenced objects being used.

Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Link: http://lkml.kernel.org/n/tip-majzgz07cm90t2tejrjy4clf@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/perf/tests/dso-data.c | 4 ++--
tools/perf/tests/hists_common.c | 6 +++++-
tools/perf/util/dso.c | 37 ++++++++++++++++++++++++++++++++++++-
tools/perf/util/dso.h | 14 +++++++++++++-
tools/perf/util/header.c | 1 +
tools/perf/util/machine.c | 15 +++++++++++----
tools/perf/util/map.c | 11 +++++++++--
tools/perf/util/probe-finder.c | 2 +-
tools/perf/util/symbol-elf.c | 2 +-
tools/perf/util/symbol.c | 2 +-
tools/perf/util/vdso.c | 1 +
11 files changed, 81 insertions(+), 14 deletions(-)

diff --git a/tools/perf/tests/dso-data.c b/tools/perf/tests/dso-data.c
index 3e41c61..a218aea 100644
--- a/tools/perf/tests/dso-data.c
+++ b/tools/perf/tests/dso-data.c
@@ -166,7 +166,7 @@ int test__dso_data(void)
free(buf);
}

- dso__delete(dso);
+ dso__put(dso);
unlink(file);
return 0;
}
@@ -226,7 +226,7 @@ static void dsos__delete(int cnt)
struct dso *dso = dsos[i];

unlink(dso->name);
- dso__delete(dso);
+ dso__put(dso);
}

free(dsos);
diff --git a/tools/perf/tests/hists_common.c b/tools/perf/tests/hists_common.c
index 915f60a..ce80b27 100644
--- a/tools/perf/tests/hists_common.c
+++ b/tools/perf/tests/hists_common.c
@@ -134,11 +134,15 @@ struct machine *setup_fake_machine(struct machines *machines)

sym = symbol__new(fsym->start, fsym->length,
STB_GLOBAL, fsym->name);
- if (sym == NULL)
+ if (sym == NULL) {
+ dso__put(dso);
goto out;
+ }

symbols__insert(&dso->symbols[MAP__FUNCTION], sym);
}
+
+ dso__put(dso);
}

return machine;
diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index ff0204a..7c0c083 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -1049,6 +1049,7 @@ struct dso *dso__new(const char *name)
INIT_LIST_HEAD(&dso->node);
INIT_LIST_HEAD(&dso->data.open_entry);
pthread_mutex_init(&dso->lock, NULL);
+ atomic_set(&dso->refcnt, 1);
}

return dso;
@@ -1083,6 +1084,19 @@ void dso__delete(struct dso *dso)
free(dso);
}

+struct dso *dso__get(struct dso *dso)
+{
+ if (dso)
+ atomic_inc(&dso->refcnt);
+ return dso;
+}
+
+void dso__put(struct dso *dso)
+{
+ if (dso && atomic_dec_and_test(&dso->refcnt))
+ dso__delete(dso);
+}
+
void dso__set_build_id(struct dso *dso, void *build_id)
{
memcpy(dso->build_id, build_id, sizeof(dso->build_id));
@@ -1153,6 +1167,27 @@ void __dsos__add(struct dsos *dsos, struct dso *dso)
{
list_add_tail(&dso->node, &dsos->head);
__dso__findlink_by_longname(&dsos->root, dso, NULL);
+ /*
+ * It is now in the linked list, grab a reference, then garbage collect
+ * this when needing memory, by looking at LRU dso instances in the
+ * list with atomic_read(&dso->refcnt) == 1, i.e. no references
+ * anywhere besides the one for the list, do, under a lock for the
+ * list: remove it from the list, then a dso__put(), that probably will
+ * be the last and will then call dso__delete(), end of life.
+ *
+ * That, or at the end of the 'struct machine' lifetime, when all
+ * 'struct dso' instances will be removed from the list, in
+ * dsos__exit(), if they have no other reference from some other data
+ * structure.
+ *
+ * E.g.: after processing a 'perf.data' file and storing references
+ * to objects instantiated while processing events, we will have
+ * references to the 'thread', 'map', 'dso' structs all from 'struct
+ * hist_entry' instances, but we may not need anything not referenced,
+ * so we might as well call machines__exit()/machines__delete() and
+ * garbage collect it.
+ */
+ dso__get(dso);
}

void dsos__add(struct dsos *dsos, struct dso *dso)
@@ -1206,7 +1241,7 @@ struct dso *dsos__findnew(struct dsos *dsos, const char *name)
{
struct dso *dso;
pthread_rwlock_wrlock(&dsos->lock);
- dso = __dsos__findnew(dsos, name);
+ dso = dso__get(__dsos__findnew(dsos, name));
pthread_rwlock_unlock(&dsos->lock);
return dso;
}
diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index c16ab5d..2fe98bb 100644
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -1,6 +1,7 @@
#ifndef __PERF_DSO
#define __PERF_DSO

+#include <linux/atomic.h>
#include <linux/types.h>
#include <linux/rbtree.h>
#include <stdbool.h>
@@ -179,7 +180,7 @@ struct dso {
void *priv;
u64 db_id;
};
-
+ atomic_t refcnt;
char name[0];
};

@@ -206,6 +207,17 @@ void dso__set_long_name(struct dso *dso, const char *name, bool name_allocated);

int dso__name_len(const struct dso *dso);

+struct dso *dso__get(struct dso *dso);
+void dso__put(struct dso *dso);
+
+static inline void __dso__zput(struct dso **dso)
+{
+ dso__put(*dso);
+ *dso = NULL;
+}
+
+#define dso__zput(dso) __dso__zput(&dso)
+
bool dso__loaded(const struct dso *dso, enum map_type type);

bool dso__sorted_by_name(const struct dso *dso, enum map_type type);
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index ac5aaae..21a77e7 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1277,6 +1277,7 @@ static int __event_process_build_id(struct build_id_event *bev,
sbuild_id);
pr_debug("build id event received for %s: %s\n",
dso->long_name, sbuild_id);
+ dso__put(dso);
}

err = 0;
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 0cf56d6..132e357 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -82,7 +82,7 @@ out_delete:
return NULL;
}

-static void dsos__exit(struct dsos *dsos)
+static void dsos__purge(struct dsos *dsos)
{
struct dso *pos, *n;

@@ -90,12 +90,16 @@ static void dsos__exit(struct dsos *dsos)

list_for_each_entry_safe(pos, n, &dsos->head, node) {
RB_CLEAR_NODE(&pos->rb_node);
- list_del(&pos->node);
- dso__delete(pos);
+ list_del_init(&pos->node);
+ dso__put(pos);
}

pthread_rwlock_unlock(&dsos->lock);
+}

+static void dsos__exit(struct dsos *dsos)
+{
+ dsos__purge(dsos);
pthread_rwlock_destroy(&dsos->lock);
}

@@ -524,6 +528,7 @@ static struct dso *machine__findnew_module_dso(struct machine *machine,
dso__set_long_name(dso, strdup(filename), true);
}

+ dso__get(dso);
out_unlock:
pthread_rwlock_unlock(&machine->dsos.lock);
return dso;
@@ -1205,8 +1210,10 @@ static int machine__process_kernel_mmap_event(struct machine *machine,
goto out_problem;

kernel->kernel = kernel_type;
- if (__machine__create_kernel_maps(machine, kernel) < 0)
+ if (__machine__create_kernel_maps(machine, kernel) < 0) {
+ dso__put(kernel);
goto out_problem;
+ }

if (strstr(kernel->long_name, "vmlinux"))
dso__set_short_name(kernel, "[kernel.vmlinux]", false);
diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index 365011c..1241ab9 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -132,7 +132,7 @@ void map__init(struct map *map, enum map_type type,
map->end = end;
map->pgoff = pgoff;
map->reloc = 0;
- map->dso = dso;
+ map->dso = dso__get(dso);
map->map_ip = map__map_ip;
map->unmap_ip = map__unmap_ip;
RB_CLEAR_NODE(&map->rb_node);
@@ -198,6 +198,7 @@ struct map *map__new(struct machine *machine, u64 start, u64 len,
if (type != MAP__FUNCTION)
dso__set_loaded(dso, map->type);
}
+ dso__put(dso);
}
return map;
out_delete:
@@ -224,9 +225,15 @@ struct map *map__new2(u64 start, struct dso *dso, enum map_type type)
return map;
}

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

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index c50da39..2da65a7 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -130,7 +130,7 @@ struct debuginfo *debuginfo__new(const char *path)
continue;
dinfo = __debuginfo__new(buf);
}
- dso__delete(dso);
+ dso__put(dso);

out:
/* if failed to open all distro debuginfo, open given binary */
diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index a93ba85..65f7e38 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -1016,7 +1016,7 @@ int dso__load_sym(struct dso *dso, struct map *map,
curr_map = map__new2(start, curr_dso,
map->type);
if (curr_map == NULL) {
- dso__delete(curr_dso);
+ dso__put(curr_dso);
goto out_elf_end;
}
if (adjust_kernel_syms) {
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index eaee5d3..504f2d7 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -786,7 +786,7 @@ static int dso__split_kallsyms(struct dso *dso, struct map *map, u64 delta,

curr_map = map__new2(pos->start, ndso, map->type);
if (curr_map == NULL) {
- dso__delete(ndso);
+ dso__put(ndso);
return -1;
}

diff --git a/tools/perf/util/vdso.c b/tools/perf/util/vdso.c
index c646c74..4b89118 100644
--- a/tools/perf/util/vdso.c
+++ b/tools/perf/util/vdso.c
@@ -314,6 +314,7 @@ struct dso *machine__findnew_vdso(struct machine *machine,
}

out_unlock:
+ dso__get(dso);
pthread_rwlock_unlock(&machine->dsos.lock);
return dso;
}
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