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    SubjectRe: [PATCH 1/3] jump label: add enabled/disabled state to jump label key entries
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    On Tue, 2010-11-23 at 18:43 -0500, Mathieu Desnoyers wrote:
    > * Jason Baron (jbaron@redhat.com) wrote:
    > [...]
    > > +static void update_jump_label_module(struct module *mod)
    > > +{
    > > + struct hlist_head *head;
    > > + struct hlist_node *node, *node_next, *module_node, *module_node_next;
    > > + struct jump_label_entry *e;
    > > + struct jump_label_module_entry *e_module;
    > > + struct jump_entry *iter;
    > > + int i, count;
    > > +
    > > + /* if the module doesn't have jump label entries, just return */
    > > + if (!mod->num_jump_entries)
    > > + return;
    > > +
    > > + for (i = 0; i < JUMP_LABEL_TABLE_SIZE; i++) {
    > > + head = &jump_label_table[i];
    > > + hlist_for_each_entry_safe(e, node, node_next, head, hlist) {
    > > + if (!e->enabled)
    > > + continue;
    > > + hlist_for_each_entry_safe(e_module, module_node,
    > > + module_node_next,
    > > + &(e->modules), hlist) {
    > > + if (e_module->mod != mod)
    > > + continue;
    >
    > Ouch.
    >
    > Could you iterate on the loaded/unloaded module jump labels and do hash
    > table lookups rather than doing this O(n^3) iteration ?

    This does not look O(n^3) to me.

    It's a hash table, thus the first two loops is just iterating O(n) items
    in the hash.

    And the third loop is all the modules that use a particular event.

    So it is O(n*m) where n is the number of events, and m is the number of
    modules attached to the events. And that's only if all events are used
    by those modules. The actual case is much smaller.

    -- Steve




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