perf maps: Do not use an rbtree to sort by map name

This is only used for the kernel maps, shave 24 bytes out 'struct map'
and just traverse the existing per ip rbtree to look for maps by name,
use a front end cache to reuse the last search if its the same name.

After this 'struct map' is down to just two cachelines:

  $ pahole -C map ~/bin/perf
  struct map {
  	union {
  		struct rb_node rb_node __attribute__((__aligned__(8))); /*     0    24 */
  		struct list_head node;                   /*     0    16 */
  	} __attribute__((__aligned__(8)));                                               /*     0    24 */
  	u64                        start;                /*    24     8 */
  	u64                        end;                  /*    32     8 */
  	_Bool                      erange_warned;        /*    40     1 */

  	/* XXX 3 bytes hole, try to pack */

  	u32                        priv;                 /*    44     4 */
  	u32                        prot;                 /*    48     4 */
  	u32                        flags;                /*    52     4 */
  	u64                        pgoff;                /*    56     8 */
  	/* --- cacheline 1 boundary (64 bytes) --- */
  	u64                        reloc;                /*    64     8 */
  	u32                        maj;                  /*    72     4 */
  	u32                        min;                  /*    76     4 */
  	u64                        ino;                  /*    80     8 */
  	u64                        ino_generation;       /*    88     8 */
  	u64                        (*map_ip)(struct map *, u64); /*    96     8 */
  	u64                        (*unmap_ip)(struct map *, u64); /*   104     8 */
  	struct dso *               dso;                  /*   112     8 */
  	refcount_t                 refcnt;               /*   120     4 */

  	/* size: 128, cachelines: 2, members: 17 */
  	/* sum members: 121, holes: 1, sum holes: 3 */
  	/* padding: 4 */
  	/* forced alignments: 1 */
  } __attribute__((__aligned__(8)));
  $

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-bvr8fqfgzxtgnhnwt5sssx5g@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/map_groups.c

@@ -25,7 +25,7 @@ static int check_maps(struct map_def *merged, unsigned int size, struct map_grou
 		TEST_ASSERT_VAL("wrong map start",  map->start == merged[i].start);
 		TEST_ASSERT_VAL("wrong map end",    map->end == merged[i].end);
 		TEST_ASSERT_VAL("wrong map name",  !strcmp(map->dso->name, merged[i].name));
-		TEST_ASSERT_VAL("wrong map refcnt", refcount_read(&map->refcnt) == 2);
+		TEST_ASSERT_VAL("wrong map refcnt", refcount_read(&map->refcnt) == 1);
 
 		i++;
 	}

tools/perf/util/map.c

@@ -26,7 +26,6 @@
 #include "ui/ui.h"
 
 static void __maps__insert(struct maps *maps, struct map *map);
-static void __maps__insert_name(struct maps *maps, struct map *map);
 
 static inline int is_anon_memory(const char *filename, u32 flags)
 {
@@ -566,7 +565,6 @@ u64 map__objdump_2mem(struct map *map, u64 ip)
 static void maps__init(struct maps *maps)
 {
 	maps->entries = RB_ROOT;
-	maps->names = RB_ROOT;
 	init_rwsem(&maps->lock);
 }
 
@@ -589,8 +587,6 @@ static void __maps__purge(struct maps *maps)
 	maps__for_each_entry_safe(maps, pos, next) {
 		rb_erase_init(&pos->rb_node,  &maps->entries);
 		map__put(pos);
-		rb_erase_init(&pos->rb_node_name, &maps->names);
-		map__put(pos);
 	}
 }
 
@@ -736,7 +732,6 @@ size_t map_groups__fprintf(struct map_groups *mg, FILE *fp)
 static void __map_groups__insert(struct map_groups *mg, struct map *map)
 {
 	__maps__insert(&mg->maps, map);
-	__maps__insert_name(&mg->maps, map);
 }
 
 int map_groups__fixup_overlappings(struct map_groups *mg, struct map *map, FILE *fp)
@@ -893,32 +888,10 @@ static void __maps__insert(struct maps *maps, struct map *map)
 	map__get(map);
 }
 
-static void __maps__insert_name(struct maps *maps, struct map *map)
-{
-	struct rb_node **p = &maps->names.rb_node;
-	struct rb_node *parent = NULL;
-	struct map *m;
-	int rc;
-
-	while (*p != NULL) {
-		parent = *p;
-		m = rb_entry(parent, struct map, rb_node_name);
-		rc = strcmp(m->dso->short_name, map->dso->short_name);
-		if (rc < 0)
-			p = &(*p)->rb_left;
-		else
-			p = &(*p)->rb_right;
-	}
-	rb_link_node(&map->rb_node_name, parent, p);
-	rb_insert_color(&map->rb_node_name, &maps->names);
-	map__get(map);
-}
-
 void maps__insert(struct maps *maps, struct map *map)
 {
 	down_write(&maps->lock);
 	__maps__insert(maps, map);
-	__maps__insert_name(maps, map);
 	up_write(&maps->lock);
 }
 
@@ -926,9 +899,6 @@ static void __maps__remove(struct maps *maps, struct map *map)
 {
 	rb_erase_init(&map->rb_node, &maps->entries);
 	map__put(map);
-
-	rb_erase_init(&map->rb_node_name, &maps->names);
-	map__put(map);
 }
 
 void maps__remove(struct maps *maps, struct map *map)

tools/perf/util/map.h

@@ -23,7 +23,6 @@ struct map {
 		struct rb_node	rb_node;
 		struct list_head node;
 	};
-	struct rb_node          rb_node_name;
 	u64			start;
 	u64			end;
 	bool			erange_warned;

tools/perf/util/map_groups.h

@@ -16,7 +16,6 @@ struct thread;
 
 struct maps {
 	struct rb_root      entries;
-	struct rb_root	    names;
 	struct rw_semaphore lock;
 };
 

tools/perf/util/symbol.c

@@ -1764,24 +1764,12 @@ struct map *map_groups__find_by_name(struct map_groups *mg, const char *name)
 {
 	struct maps *maps = &mg->maps;
 	struct map *map;
-	struct rb_node *node;
 
 	down_read(&maps->lock);
 
-	for (node = maps->names.rb_node; node; ) {
-		int rc;
-
-		map = rb_entry(node, struct map, rb_node_name);
-
-		rc = strcmp(map->dso->short_name, name);
-		if (rc < 0)
-			node = node->rb_left;
-		else if (rc > 0)
-			node = node->rb_right;
-		else
-
+	maps__for_each_entry(maps, map)
+		if (strcmp(map->dso->short_name, name) == 0)
 			goto out_unlock;
-	}
 
 	map = NULL;