linux-kernel - Re: [PATCH 1/3] jump label: add enabled/disabled state to jump label key entries

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Date:	Tue, 23 Nov 2010 18:43:55 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Jason Baron <jbaron@...hat.com>
Cc:	rostedt@...dmis.org, mingo@...e.hu, peterz@...radead.org,
	hpa@...or.com, tglx@...utronix.de, andi@...stfloor.org,
	roland@...hat.com, rth@...hat.com, masami.hiramatsu.pt@...achi.com,
	fweisbec@...il.com, avi@...hat.com, davem@...emloft.net,
	sam@...nborg.org, ddaney@...iumnetworks.com,
	michael@...erman.id.au, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] jump label: add enabled/disabled state to jump
	label key entries

* Jason Baron (jbaron@...hat.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 ?

Thanks,

Mathieu

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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