perf dsos: Switch backing storage to array from rbtree/list

DSOs were held on a list for fast iteration and in an rbtree for fast
finds.

Switch to using a lazily sorted array where iteration is just iterating
through the array and binary searches are the same complexity as
searching the rbtree.

The find may need to sort the array first which does increase the
complexity, but add operations have lower complexity and overall the
complexity should remain about the same.

The set name operations on the dso just records that the array is no
longer sorted, avoiding complexity in rebalancing the rbtree.

Tighter locking discipline is enforced to avoid the array being resorted
while long and short names or ids are changed.

The array is smaller in size, replacing 6 pointers with 2, and so even
with extra allocated space in the array, the array may be 50%
unoccupied, the memory saving should be at least 2x.

Committer testing:

On a previous version of this patchset we were getting a lot of warnings
about deleting a DSO still on a list, now it is ok:

  root@x1:~# perf probe -l
  root@x1:~# perf probe finish_task_switch
  Added new event:
    probe:finish_task_switch (on finish_task_switch)

  You can now use it in all perf tools, such as:

  	perf record -e probe:finish_task_switch -aR sleep 1

  root@x1:~# perf probe -l
    probe:finish_task_switch (on finish_task_switch@kernel/sched/core.c)
  root@x1:~# perf trace -e probe:finish_task_switch/max-stack=8/ --max-events=1
       0.000 migration/0/19 probe:finish_task_switch(__probe_ip: -1894408688)
                                         finish_task_switch.isra.0 ([kernel.kallsyms])
                                         __schedule ([kernel.kallsyms])
                                         schedule ([kernel.kallsyms])
                                         smpboot_thread_fn ([kernel.kallsyms])
                                         kthread ([kernel.kallsyms])
                                         ret_from_fork ([kernel.kallsyms])
                                         ret_from_fork_asm ([kernel.kallsyms])
  root@x1:~#
  root@x1:~# perf probe -d probe:*
  Removed event: probe:finish_task_switch
  root@x1:~# perf probe -l
  root@x1:~#

I also ran the full 'perf test' suite after applying this one, no
regressions.

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Ben Gainey <ben.gainey@arm.com>
Cc: Changbin Du <changbin.du@huawei.com>
Cc: Chengen Du <chengen.du@canonical.com>
Cc: Colin Ian King <colin.i.king@gmail.com>
Cc: Dima Kogan <dima@secretsauce.net>
Cc: Ilkka Koskinen <ilkka@os.amperecomputing.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@linux.dev>
Cc: Li Dong <lidong@vivo.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paran Lee <p4ranlee@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <song@kernel.org>
Cc: Sun Haiyong <sunhaiyong@loongson.cn>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>
Cc: Yanteng Si <siyanteng@loongson.cn>
Cc: zhaimingbing <zhaimingbing@cmss.chinamobile.com>
Link: https://lore.kernel.org/r/20240504213803.218974-2-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Author: captain5050

tools/perf/util/dso.c

@@ -1241,35 +1241,35 @@ struct dso *machine__findnew_kernel(struct machine *machine, const char *name,
 	return dso;
 }
 
-static void dso__set_long_name_id(struct dso *dso, const char *name, struct dso_id *id, bool name_allocated)
+static void dso__set_long_name_id(struct dso *dso, const char *name, bool name_allocated)
 {
-	struct rb_root *root = dso->root;
+	struct dsos *dsos = dso->dsos;
 
 	if (name == NULL)
 		return;
 
-	if (dso->long_name_allocated)
-		free((char *)dso->long_name);
-
-	if (root) {
-		rb_erase(&dso->rb_node, root);
+	if (dsos) {
 		/*
-		 * __dsos__findnew_link_by_longname_id() isn't guaranteed to
-		 * add it back, so a clean removal is required here.
+		 * Need to avoid re-sorting the dsos breaking by non-atomically
+		 * renaming the dso.
 		 */
-		RB_CLEAR_NODE(&dso->rb_node);
-		dso->root = NULL;
+		down_write(&dsos->lock);
 	}
 
+	if (dso->long_name_allocated)
+		free((char *)dso->long_name);
+
 	dso->long_name		 = name;
 	dso->long_name_len	 = strlen(name);
 	dso->long_name_allocated = name_allocated;
 
-	if (root)
-		__dsos__findnew_link_by_longname_id(root, dso, NULL, id);
+	if (dsos) {
+		dsos->sorted = false;
+		up_write(&dsos->lock);
+	}
 }
 
-static int __dso_id__cmp(struct dso_id *a, struct dso_id *b)
+static int __dso_id__cmp(const struct dso_id *a, const struct dso_id *b)
 {
 	if (a->maj > b->maj) return -1;
 	if (a->maj < b->maj) return 1;
@@ -1297,23 +1297,30 @@ static int __dso_id__cmp(struct dso_id *a, struct dso_id *b)
 	return 0;
 }
 
-bool dso_id__empty(struct dso_id *id)
+bool dso_id__empty(const struct dso_id *id)
 {
 	if (!id)
 		return true;
 
 	return !id->maj && !id->min && !id->ino && !id->ino_generation;
 }
 
-void dso__inject_id(struct dso *dso, struct dso_id *id)
+void __dso__inject_id(struct dso *dso, struct dso_id *id)
 {
+	struct dsos *dsos = dso->dsos;
+
+	/* dsos write lock held by caller. */
+
 	dso->id.maj = id->maj;
 	dso->id.min = id->min;
 	dso->id.ino = id->ino;
 	dso->id.ino_generation = id->ino_generation;
+
+	if (dsos)
+		dsos->sorted = false;
 }
 
-int dso_id__cmp(struct dso_id *a, struct dso_id *b)
+int dso_id__cmp(const struct dso_id *a, const struct dso_id *b)
 {
 	/*
 	 * The second is always dso->id, so zeroes if not set, assume passing
@@ -1332,20 +1339,34 @@ int dso__cmp_id(struct dso *a, struct dso *b)
 
 void dso__set_long_name(struct dso *dso, const char *name, bool name_allocated)
 {
-	dso__set_long_name_id(dso, name, NULL, name_allocated);
+	dso__set_long_name_id(dso, name, name_allocated);
 }
 
 void dso__set_short_name(struct dso *dso, const char *name, bool name_allocated)
 {
+	struct dsos *dsos = dso->dsos;
+
 	if (name == NULL)
 		return;
 
+	if (dsos) {
+		/*
+		 * Need to avoid re-sorting the dsos breaking by non-atomically
+		 * renaming the dso.
+		 */
+		down_write(&dsos->lock);
+	}
 	if (dso->short_name_allocated)
 		free((char *)dso->short_name);
 
 	dso->short_name		  = name;
 	dso->short_name_len	  = strlen(name);
 	dso->short_name_allocated = name_allocated;
+
+	if (dsos) {
+		dsos->sorted = false;
+		up_write(&dsos->lock);
+	}
 }
 
 int dso__name_len(const struct dso *dso)
@@ -1381,7 +1402,7 @@ struct dso *dso__new_id(const char *name, struct dso_id *id)
 		strcpy(dso->name, name);
 		if (id)
 			dso->id = *id;
-		dso__set_long_name_id(dso, dso->name, id, false);
+		dso__set_long_name_id(dso, dso->name, false);
 		dso__set_short_name(dso, dso->name, false);
 		dso->symbols = RB_ROOT_CACHED;
 		dso->symbol_names = NULL;
@@ -1406,9 +1427,6 @@ struct dso *dso__new_id(const char *name, struct dso_id *id)
 		dso->is_kmod = 0;
 		dso->needs_swap = DSO_SWAP__UNSET;
 		dso->comp = COMP_ID__NONE;
-		RB_CLEAR_NODE(&dso->rb_node);
-		dso->root = NULL;
-		INIT_LIST_HEAD(&dso->node);
 		INIT_LIST_HEAD(&dso->data.open_entry);
 		mutex_init(&dso->lock);
 		refcount_set(&dso->refcnt, 1);
@@ -1424,9 +1442,8 @@ struct dso *dso__new(const char *name)
 
 void dso__delete(struct dso *dso)
 {
-	if (!RB_EMPTY_NODE(&dso->rb_node))
-		pr_err("DSO %s is still in rbtree when being deleted!\n",
-		       dso->long_name);
+	if (dso->dsos)
+		pr_err("DSO %s is still in rbtree when being deleted!\n", dso->long_name);
 
 	/* free inlines first, as they reference symbols */
 	inlines__tree_delete(&dso->inlined_nodes);

tools/perf/util/dso.h

@@ -146,9 +146,7 @@ struct auxtrace_cache;
 
 struct dso {
 	struct mutex	 lock;
-	struct list_head node;
-	struct rb_node	 rb_node;	/* rbtree node sorted by long name */
-	struct rb_root	 *root;		/* root of rbtree that rb_node is in */
+	struct dsos	 *dsos;
 	struct rb_root_cached symbols;
 	struct symbol	 **symbol_names;
 	size_t		 symbol_names_len;
@@ -238,8 +236,8 @@ static inline void dso__set_loaded(struct dso *dso)
 	dso->loaded = true;
 }
 
-int dso_id__cmp(struct dso_id *a, struct dso_id *b);
-bool dso_id__empty(struct dso_id *id);
+int dso_id__cmp(const struct dso_id *a, const struct dso_id *b);
+bool dso_id__empty(const struct dso_id *id);
 
 struct dso *dso__new_id(const char *name, struct dso_id *id);
 struct dso *dso__new(const char *name);
@@ -248,7 +246,7 @@ void dso__delete(struct dso *dso);
 int dso__cmp_id(struct dso *a, struct dso *b);
 void dso__set_short_name(struct dso *dso, const char *name, bool name_allocated);
 void dso__set_long_name(struct dso *dso, const char *name, bool name_allocated);
-void dso__inject_id(struct dso *dso, struct dso_id *id);
+void __dso__inject_id(struct dso *dso, struct dso_id *id);
 
 int dso__name_len(const struct dso *dso);