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@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/n/tip-majzgz07cm90t2tejrjy4clf@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/tests/dso-data.c b/tools/perf/tests/dso-data.c
index 3e41c61bd8610406fcc4dd2afa45198a6d32be70..a218aeaf56a002396bf0d0db9ef0e457a7445c9f 100644 (file)
--- 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 915f60af6a0ebe6fba525e0f65b1e8205a1da025..ce80b274b097332d02b5502fb0c5b88fc6d6016a 100644 (file)
--- 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 ff0204ac4321e2e67ddd2c105253a62e1d044179..7c0c08386a1d9d6fb5e8cba6c838e5c3c1949bd7 100644 (file)
--- 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 c16ab5d849c39061e51d785683b63ea5beff2655..2fe98bb0e95b0d4b88fb58f2fc28daee875a13bb 100644 (file)
--- 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 ac5aaaeed7ffd515d882a14eb329d0dd383f88b7..21a77e7a171e8aa0664d5caf0737f141bc96e62f 100644 (file)
--- 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 0cf56d6f073ad2c527b3f95a91b66bdff6b5e591..132e357651019911a9d7eb83b491650fe4dddd94 100644 (file)
--- 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 365011c233a68864a909c6480d4c5a6b99258f85..1241ab989cf5d72d46b0f9493770c837d557f32e 100644 (file)
--- 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 c50da392e2562a377e3efa9464e257f27075bcea..2da65a7108932857bd585681eb0fac195f0c850b 100644 (file)
--- 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 a93ba85509b2875f6ad1c76799219f0a44c221d3..65f7e389ae0996cae131cbfbcd2196181f15f1e7 100644 (file)
--- 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 eaee5d32d39dc3dfa38d46eeabbfb7bca5e356c7..504f2d73b7eefe2699349ac75c5cc3b875961375 100644 (file)
--- 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 c646c74c34f8420e63a9a2d7d3c2b15e937d8434..4b89118f158db458ae29cca6d20b093d81392cf6 100644 (file)
--- 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;
 }