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

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Message-ID: <87mw3zlght.fsf@rustcorp.com.au>
Date:	Fri, 27 Feb 2015 22:21:26 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Peter Zijlstra <peterz@...radead.org>,
	Andi Kleen <ak@...ux.intel.com>
Cc:	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, mingo@...nel.org
Subject: Re: [RFC][PATCH] module: Optimize __module_address() using a latched RB-tree

Peter Zijlstra <peterz@...radead.org> writes:
> On Thu, Feb 26, 2015 at 12:43:09PM +0100, Peter Zijlstra wrote:
>
> Assuming struct module is cacheline aligned, Rusty? from what I can find
> its squirreled away in some data structure:
>
>   mod = (void *)info->sechdrs[info->index.mod].sh_addr
>
> And I can't seem to quickly find its alignment. If its not cacheline
> aligned, can we make it so?

If the ELF says to align it, it will be aligned.  Thus your patch
below should make it Just Work:

> @@ -278,7 +276,7 @@
>  	int (*init)(void);
>  
>  	/* If this is non-NULL, vfree after init() returns */
> -	void *module_init;
> +	void *module_init	____cacheline_aligned;
>  
>  	/* Here is the actual code + data, vfree'd on unload. */
>  	void *module_core;

Cheers,
Rusty.
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