linux-kernel - Re: [RFC][PATCH] module: Optimize __module

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Message-ID: <20150226120038.GA4779@gmail.com>
Date:	Thu, 26 Feb 2015 13:00:38 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Andi Kleen <ak@...ux.intel.com>, Andi Kleen <andi@...stfloor.org>,
	x86@...nel.org, linux-kernel@...r.kernel.org,
	mathieu.desnoyers@...icios.com, oleg@...hat.com,
	paulmck@...ux.vnet.ibm.com, rusty@...tcorp.com.au
Subject: Re: [RFC][PATCH] module: Optimize __module_address() using a latched
 RB-tree


* Peter Zijlstra <peterz@...radead.org> wrote:

> +static struct module *mod_tree_find(unsigned long addr)
> +{
> +	struct module *m;
> +	unsigned int seq;
> +
> +	do {
> +		seq = raw_read_seqcount(&mod_tree.seq);
> +		m = __tree_find(&mod_tree.tree[seq & 1], addr);
> +	} while (read_seqcount_retry(&mod_tree.seq, seq));
> +
> +	return m;
> +}

Btw., if your approach works out fine I bet we could add 
one more optimization as well: a PER_CPU(last_module_found) 
front cache would help as well, as usually there's quite a 
bit of repetition between addresses being looked up and the 
resulting modules.

Thanks,

	Ingo
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