perf: Keep track of the max depth of a callchain

In order to implement callchains collapsing, we need to keep
track of the maximum depth in a histogram tree of callchains.
This way we'll avoid allocating an arbitrary temporary buffer
size on callchain merge time.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Christoph Hellwig <hch@infradead.org>

1 files changed, 14 insertions, 8 deletions

diff --git a/tools/perf/util/callchain.h b/tools/perf/util/callchain.h
index 624a96c636fd..9b93a38e88ec 100644
--- a/tools/perf/util/callchain.h
+++ b/tools/perf/util/callchain.h
@@ -26,9 +26,14 @@ struct callchain_node {
         u64                     children_hit;
 };
 
+struct callchain_root {
+        u64                     max_depth;
+        struct callchain_node   node;
+};
+
 struct callchain_param;
 
-typedef void (*sort_chain_func_t)(struct rb_root *, struct callchain_node *,
+typedef void (*sort_chain_func_t)(struct rb_root *, struct callchain_root *,
                                  u64, struct callchain_param *);
 
 struct callchain_param {
@@ -44,14 +49,15 @@ struct callchain_list {
         struct list_head        list;
 };
 
-static inline void callchain_init(struct callchain_node *node)
+static inline void callchain_init(struct callchain_root *root)
 {
-        INIT_LIST_HEAD(&node->brothers);
-        INIT_LIST_HEAD(&node->children);
-        INIT_LIST_HEAD(&node->val);
+        INIT_LIST_HEAD(&root->node.brothers);
+        INIT_LIST_HEAD(&root->node.children);
+        INIT_LIST_HEAD(&root->node.val);
 
-        node->parent = NULL;
-        node->hit = 0;
+        root->node.parent = NULL;
+        root->node.hit = 0;
+        root->max_depth = 0;
 }
 
 static inline u64 cumul_hits(struct callchain_node *node)
@@ -60,7 +66,7 @@ static inline u64 cumul_hits(struct callchain_node *node)
 }
 
 int register_callchain_param(struct callchain_param *param);
-int append_chain(struct callchain_node *root, struct ip_callchain *chain,
+int append_chain(struct callchain_root *root, struct ip_callchain *chain,
                  struct map_symbol *syms, u64 period);
 
 bool ip_callchain__valid(struct ip_callchain *chain, const event_t *event);