Date: Thu, 26 Feb 2015 13:00:38 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Andi Kleen <ak@linux.intel.com>, Andi Kleen <andi@firstfloor.org>,
        x86@kernel.org, linux-kernel@vger.kernel.org,
        mathieu.desnoyers@efficios.com, oleg@redhat.com,
        paulmck@linux.vnet.ibm.com, rusty@rustcorp.com.au
Subject: Re: [RFC][PATCH] module: Optimize __module_address() using a latched
 RB-tree
Message-ID: <20150226120038.GA4779@gmail.com>
References: <1424482737-958-1-git-send-email-andi@firstfloor.org>
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 <20150223174340.GD27767@tassilo.jf.intel.com>
 <20150226114309.GR21418@twins.programming.kicks-ass.net>
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* Peter Zijlstra <peterz@infradead.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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