callchain.c

/*
 * Copyright (C) 2009-2011, Frederic Weisbecker <fweisbec@gmail.com>
 *
 * 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>
#include <stdio.h>
#include <stdbool.h>
#include <errno.h>
#include <math.h>

#include "hist.h"
#include "util.h"
#include "callchain.h"

__thread struct callchain_cursor callchain_cursor;

#define chain_for_each_child(child, parent)	\
	list_for_each_entry(child, &parent->children, siblings)

#define chain_for_each_child_safe(child, next, parent)	\
	list_for_each_entry_safe(child, next, &parent->children, siblings)

static void
rb_insert_callchain(struct rb_root *root, struct callchain_node *chain,
		    enum chain_mode mode)
{
	struct rb_node **p = &root->rb_node;
	struct rb_node *parent = NULL;
	struct callchain_node *rnode;
	u64 chain_cumul = callchain_cumul_hits(chain);

	while (*p) {
		u64 rnode_cumul;

		parent = *p;
		rnode = rb_entry(parent, struct callchain_node, rb_node);
		rnode_cumul = callchain_cumul_hits(rnode);

		switch (mode) {
		case CHAIN_FLAT:
			if (rnode->hit < chain->hit)
				p = &(*p)->rb_left;
			else
				p = &(*p)->rb_right;
			break;
		case CHAIN_GRAPH_ABS: /* Falldown */
		case CHAIN_GRAPH_REL:
			if (rnode_cumul < chain_cumul)
				p = &(*p)->rb_left;
			else
				p = &(*p)->rb_right;
			break;
		case CHAIN_NONE:
		default:
			break;
		}
	}

	rb_link_node(&chain->rb_node, parent, p);
	rb_insert_color(&chain->rb_node, root);
}

static void
__sort_chain_flat(struct rb_root *rb_root, struct callchain_node *node,
		  u64 min_hit)
{
	struct callchain_node *child;

	chain_for_each_child(child, node)
		__sort_chain_flat(rb_root, child, min_hit);

	if (node->hit && node->hit >= min_hit)
		rb_insert_callchain(rb_root, node, CHAIN_FLAT);
}

/*
 * Once we get every callchains from the stream, we can now
 * sort them by hit
 */
static void
sort_chain_flat(struct rb_root *rb_root, struct callchain_root *root,
		u64 min_hit, struct callchain_param *param __maybe_unused)
{
	__sort_chain_flat(rb_root, &root->node, min_hit);
}

static void __sort_chain_graph_abs(struct callchain_node *node,
				   u64 min_hit)
{
	struct callchain_node *child;

	node->rb_root = RB_ROOT;

	chain_for_each_child(child, node) {
		__sort_chain_graph_abs(child, min_hit);
		if (callchain_cumul_hits(child) >= min_hit)
			rb_insert_callchain(&node->rb_root, child,
					    CHAIN_GRAPH_ABS);
	}
}

static void
sort_chain_graph_abs(struct rb_root *rb_root, struct callchain_root *chain_root,
		     u64 min_hit, struct callchain_param *param __maybe_unused)
{
	__sort_chain_graph_abs(&chain_root->node, min_hit);
	rb_root->rb_node = chain_root->node.rb_root.rb_node;
}

static void __sort_chain_graph_rel(struct callchain_node *node,
				   double min_percent)
{
	struct callchain_node *child;
	u64 min_hit;

	node->rb_root = RB_ROOT;
	min_hit = ceil(node->children_hit * min_percent);

	chain_for_each_child(child, node) {
		__sort_chain_graph_rel(child, min_percent);
		if (callchain_cumul_hits(child) >= min_hit)
			rb_insert_callchain(&node->rb_root, child,
					    CHAIN_GRAPH_REL);
	}
}

static void
sort_chain_graph_rel(struct rb_root *rb_root, struct callchain_root *chain_root,
		     u64 min_hit __maybe_unused, struct callchain_param *param)
{
	__sort_chain_graph_rel(&chain_root->node, param->min_percent / 100.0);
	rb_root->rb_node = chain_root->node.rb_root.rb_node;
}

int callchain_register_param(struct callchain_param *param)
{
	switch (param->mode) {
	case CHAIN_GRAPH_ABS:
		param->sort = sort_chain_graph_abs;
		break;
	case CHAIN_GRAPH_REL:
		param->sort = sort_chain_graph_rel;
		break;
	case CHAIN_FLAT:
		param->sort = sort_chain_flat;
		break;
	case CHAIN_NONE:
	default:
		return -1;
	}
	return 0;
}

/*
 * 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;

	new = zalloc(sizeof(*new));
	if (!new) {
		perror("not enough memory to create child for code path tree");
		return NULL;
	}
	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);

		chain_for_each_child(next, new)
			next->parent = new;
	}
	list_add_tail(&new->siblings, &parent->children);

	return new;
}


/*
 * Fill the node with callchain values
 */
static void
fill_node(struct callchain_node *node, struct callchain_cursor *cursor)
{
	struct callchain_cursor_node *cursor_node;

	node->val_nr = cursor->nr - cursor->pos;
	if (!node->val_nr)
		pr_warning("Warning: empty node in callchain tree\n");

	cursor_node = callchain_cursor_current(cursor);

	while (cursor_node) {
		struct callchain_list *call;

		call = zalloc(sizeof(*call));
		if (!call) {
			perror("not enough memory for the code path tree");
			return;
		}
		call->ip = cursor_node->ip;
		call->ms.sym = cursor_node->sym;
		call->ms.map = cursor_node->map;
		list_add_tail(&call->list, &node->val);

		callchain_cursor_advance(cursor);
		cursor_node = callchain_cursor_current(cursor);
	}
}

static void
add_child(struct callchain_node *parent,
	  struct callchain_cursor *cursor,
	  u64 period)
{
	struct callchain_node *new;

	new = create_child(parent, false);
	fill_node(new, cursor);

	new->children_hit = 0;
	new->hit = period;
}

/*
 * 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 callchain_cursor *cursor,
		struct callchain_list *to_split,
		u64 idx_parents, u64 idx_local, u64 period)
{
	struct callchain_node *new;
	struct list_head *old_tail;
	unsigned int idx_total = idx_parents + idx_local;

	/* split */
	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;

	/* split the hits */
	new->hit = parent->hit;
	new->children_hit = parent->children_hit;
	parent->children_hit = callchain_cumul_hits(new);
	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 < cursor->nr) {
		parent->hit = 0;
		add_child(parent, cursor, period);
		parent->children_hit += period;
	} else {
		parent->hit = period;
	}
}

static int
append_chain(struct callchain_node *root,
	     struct callchain_cursor *cursor,
	     u64 period);

static void
append_chain_children(struct callchain_node *root,
		      struct callchain_cursor *cursor,
		      u64 period)
{
	struct callchain_node *rnode;

	/* lookup in childrens */
	chain_for_each_child(rnode, root) {
		unsigned int ret = append_chain(rnode, cursor, period);

		if (!ret)
			goto inc_children_hit;
	}
	/* nothing in children, add to the current node */
	add_child(root, cursor, period);

inc_children_hit:
	root->children_hit += period;
}

static int
append_chain(struct callchain_node *root,
	     struct callchain_cursor *cursor,
	     u64 period)
{
	struct callchain_cursor_node *curr_snap = cursor->curr;
	struct callchain_list *cnode;
	u64 start = cursor->pos;
	bool found = false;
	u64 matches;

	/*
	 * Lookup in the current node
	 * If we have a symbol, then compare the start to match
	 * anywhere inside a function, unless function
	 * mode is disabled.
	 */
	list_for_each_entry(cnode, &root->val, list) {
		struct callchain_cursor_node *node;
		struct symbol *sym;

		node = callchain_cursor_current(cursor);
		if (!node)
			break;

		sym = node->sym;

		if (cnode->ms.sym && sym &&
		    callchain_param.key == CCKEY_FUNCTION) {
			if (cnode->ms.sym->start != sym->start)
				break;
		} else if (cnode->ip != node->ip)
			break;

		if (!found)
			found = true;

		callchain_cursor_advance(cursor);
	}

	/* matches not, relay on the parent */
	if (!found) {
		cursor->curr = curr_snap;
		cursor->pos = start;
		return -1;
	}

	matches = cursor->pos - start;

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

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

	/* We match the node and still have a part remaining */
	append_chain_children(root, cursor, period);

	return 0;
}

int callchain_append(struct callchain_root *root,
		     struct callchain_cursor *cursor,
		     u64 period)
{
	if (!cursor->nr)
		return 0;

	callchain_cursor_commit(cursor);

	append_chain_children(&root->node, cursor, period);

	if (cursor->nr > root->max_depth)
		root->max_depth = cursor->nr;

	return 0;
}

static int
merge_chain_branch(struct callchain_cursor *cursor,
		   struct callchain_node *dst, struct callchain_node *src)
{
	struct callchain_cursor_node **old_last = cursor->last;
	struct callchain_node *child, *next_child;
	struct callchain_list *list, *next_list;
	int old_pos = cursor->nr;
	int err = 0;

	list_for_each_entry_safe(list, next_list, &src->val, list) {
		callchain_cursor_append(cursor, list->ip,
					list->ms.map, list->ms.sym);
		list_del(&list->list);
		free(list);
	}

	if (src->hit) {
		callchain_cursor_commit(cursor);
		append_chain_children(dst, cursor, src->hit);
	}

	chain_for_each_child_safe(child, next_child, src) {
		err = merge_chain_branch(cursor, dst, child);
		if (err)
			break;

		list_del(&child->siblings);
		free(child);
	}

	cursor->nr = old_pos;
	cursor->last = old_last;

	return err;
}

int callchain_merge(struct callchain_cursor *cursor,
		    struct callchain_root *dst, struct callchain_root *src)
{
	return merge_chain_branch(cursor, &dst->node, &src->node);
}

int callchain_cursor_append(struct callchain_cursor *cursor,
			    u64 ip, struct map *map, struct symbol *sym)
{
	struct callchain_cursor_node *node = *cursor->last;

	if (!node) {
		node = calloc(1, sizeof(*node));
		if (!node)
			return -ENOMEM;

		*cursor->last = node;
	}

	node->ip = ip;
	node->map = map;
	node->sym = sym;

	cursor->nr++;

	cursor->last = &node->next;

	return 0;
}