[PATCH 3/3] perfcounter: Various fixes for callchains

Frederic Weisbecker
2009-07-01T03:36:07Z

The symbol resolving has of course revealed some bugs
in the callchain tree handling.
This patch fixes some of them, including:

- inherit the children from the parents while splitting a node
- fix list range moving
- fix indexes setting in callchains
- create a child on the current node if the path doesn't match in
the existent children (was only done on the root)
- compare using symbols when possible so that we can match a function
using any ip inside by referring to its start address.

The practical effects are

- remove double callchains
- fix upside down or any random order of callchains
- fix wrong paths
- fix bad hits and percentage accounts

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
tools/perf/util/callchain.c | 122 +++++++++++++++++++++++++++++++-----------
1 files changed, 90 insertions(+), 32 deletions(-)

diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
index 6568cb1..440db12 100644
--- a/tools/perf/util/callchain.c
+++ b/tools/perf/util/callchain.c
@@ -4,6 +4,9 @@
* Handle the callchains from the stream in an ad-hoc radix tree and then
* sort them in an rbtree.
*
+ * Using a radix for code path provides a fast retrieval and factorizes
+ * memory use. Also that lets us use the paths in a hierarchical graph view.
+ *
*/

#include <stdlib.h>
@@ -14,7 +17,8 @@
#include "callchain.h"

-static void rb_insert_callchain(struct rb_root *root, struct callchain_node *chain)
+static void
+rb_insert_callchain(struct rb_root *root, struct callchain_node *chain)
{
struct rb_node **p = &root->rb_node;
struct rb_node *parent = NULL;
@@ -49,7 +53,12 @@ void sort_chain_to_rbtree(struct rb_root *rb_root, struct callchain_node *node)
rb_insert_callchain(rb_root, node);
}

-static struct callchain_node *create_child(struct callchain_node *parent)
+/*
+ * Create a child for a parent. If inherit_children, then the new child
+ * will become the new parent of it's parent children
+ */
+static struct callchain_node *
+create_child(struct callchain_node *parent, bool inherit_children)
{
struct callchain_node *new;

@@ -61,14 +70,27 @@ static struct callchain_node *create_child(struct callchain_node *parent)
new->parent = parent;
INIT_LIST_HEAD(&new->children);
INIT_LIST_HEAD(&new->val);
+
+ if (inherit_children) {
+ struct callchain_node *next;
+
+ list_splice(&parent->children, &new->children);
+ INIT_LIST_HEAD(&parent->children);
+
+ list_for_each_entry(next, &new->children, brothers)
+ next->parent = new;
+ }
list_add_tail(&new->brothers, &parent->children);

return new;
}

+/*
+ * Fill the node with callchain values
+ */
static void
-fill_node(struct callchain_node *node, struct ip_callchain *chain, int start,
- struct symbol **syms)
+fill_node(struct callchain_node *node, struct ip_callchain *chain,
+ int start, struct symbol **syms)
{
int i;

@@ -84,54 +106,80 @@ fill_node(struct callchain_node *node, struct ip_callchain *chain, int start,
call->sym = syms[i];
list_add_tail(&call->list, &node->val);
}
- node->val_nr = i - start;
+ node->val_nr = chain->nr - start;
+ if (!node->val_nr)
+ printf("Warning: empty node in callchain tree\n");
}

-static void add_child(struct callchain_node *parent, struct ip_callchain *chain,
- struct symbol **syms)
+static void
+add_child(struct callchain_node *parent, struct ip_callchain *chain,
+ int start, struct symbol **syms)
{
struct callchain_node *new;

- new = create_child(parent);
- fill_node(new, chain, parent->val_nr, syms);
+ new = create_child(parent, false);
+ fill_node(new, chain, start, syms);

new->hit = 1;
}

+/*
+ * Split the parent in two parts (a new child is created) and
+ * give a part of its callchain to the created child.
+ * Then create another child to host the given callchain of new branch
+ */
static void
split_add_child(struct callchain_node *parent, struct ip_callchain *chain,
- struct callchain_list *to_split, int idx, struct symbol **syms)
+ struct callchain_list *to_split, int idx_parents, int idx_local,
+ struct symbol **syms)
{
struct callchain_node *new;
+ struct list_head *old_tail;
+ int idx_total = idx_parents + idx_local;

/* split */
- new = create_child(parent);
- list_move_tail(&to_split->list, &new->val);
- new->hit = parent->hit;
- parent->hit = 0;
- parent->val_nr = idx;
+ new = create_child(parent, true);
+
+ /* split the callchain and move a part to the new child */
+ old_tail = parent->val.prev;
+ list_del_range(&to_split->list, old_tail);
+ new->val.next = &to_split->list;
+ new->val.prev = old_tail;
+ to_split->list.prev = &new->val;
+ old_tail->next = &new->val;

- /* create the new one */
- add_child(parent, chain, syms);
+ /* split the hits */
+ new->hit = parent->hit;
+ new->val_nr = parent->val_nr - idx_local;
+ parent->val_nr = idx_local;
+
+ /* create a new child for the new branch if any */
+ if (idx_total < chain->nr) {
+ parent->hit = 0;
+ add_child(parent, chain, idx_total, syms);
+ } else {
+ parent->hit = 1;
+ }
}

static int
__append_chain(struct callchain_node *root, struct ip_callchain *chain,
int start, struct symbol **syms);

-static int
+static void
__append_chain_children(struct callchain_node *root, struct ip_callchain *chain,
- struct symbol **syms)
+ struct symbol **syms, int start)
{
struct callchain_node *rnode;

/* lookup in childrens */
list_for_each_entry(rnode, &root->children, brothers) {
- int ret = __append_chain(rnode, chain, root->val_nr, syms);
+ int ret = __append_chain(rnode, chain, start, syms);
if (!ret)
- return 0;
+ return;
}
- return -1;
+ /* nothing in children, add to the current node */
+ add_child(root, chain, start, syms);
}

static int
@@ -142,14 +190,22 @@ __append_chain(struct callchain_node *root, struct ip_callchain *chain,
int i = start;
bool found = false;

- /* lookup in the current node */
+ /*
+ * Lookup in the current node
+ * If we have a symbol, then compare the start to match
+ * anywhere inside a function.
+ */
list_for_each_entry(cnode, &root->val, list) {
- if (cnode->ip != chain->ips[i++])
+ if (i == chain->nr)
+ break;
+ if (cnode->sym && syms[i]) {
+ if (cnode->sym->start != syms[i]->start)
+ break;
+ } else if (cnode->ip != chain->ips[i])
break;
if (!found)
found = true;
- if (i == chain->nr)
- break;
+ i++;
}

/* matches not, relay on the parent */
@@ -157,23 +213,25 @@ __append_chain(struct callchain_node *root, struct ip_callchain *chain,
return -1;

/* we match only a part of the node. Split it and add the new chain */
- if (i < root->val_nr) {
- split_add_child(root, chain, cnode, i, syms);
+ if (i - start < root->val_nr) {
+ split_add_child(root, chain, cnode, start, i - start, syms);
return 0;
}

/* we match 100% of the path, increment the hit */
- if (i == root->val_nr) {
+ if (i - start == root->val_nr && i == chain->nr) {
root->hit++;
return 0;
}

- return __append_chain_children(root, chain, syms);
+ /* We match the node and still have a part remaining */
+ __append_chain_children(root, chain, syms, i);
+
+ return 0;
}

void append_chain(struct callchain_node *root, struct ip_callchain *chain,
struct symbol **syms)
{
- if (__append_chain_children(root, chain, syms) == -1)
- add_child(root, chain, syms);
+ __append_chain_children(root, chain, syms, 0);
}
--
1.6.2.3