callchain.c

Go to the documentation of this file.

/*
 * Copyright (C) 2009-2011, Frederic Weisbecker <[email protected]>
 *
 * 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 "util.h"
#include "callchain.h"

__thread struct callchain_cursor callchain_cursor;

bool ip_callchain__valid(struct ip_callchain *chain,
             const union perf_event *event)
{
    unsigned int chain_size = event->header.size;
    chain_size -= (unsigned long)&event->ip.__more_data - (unsigned long)event;
    return chain->nr * sizeof(u64) <= chain_size;
}

#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.
     */
    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) {
            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(sizeof(*node), 1);
        if (!node)
            return -ENOMEM;

        *cursor->last = node;
    }

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

    cursor->nr++;

    cursor->last = &node->next;

    return 0;
}