Date: Thu, 26 Feb 2015 18:16:26 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andi Kleen <ak@linux.intel.com>, Andi Kleen <andi@firstfloor.org>,
        x86@kernel.org, linux-kernel@vger.kernel.org, oleg@redhat.com,
        paulmck@linux.vnet.ibm.com, rusty@rustcorp.com.au, mingo@kernel.org
Subject: Re: [RFC][PATCH] module: Optimize __module_address() using a latched
 RB-tree
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On Thu, Feb 26, 2015 at 04:55:35PM +0000, Mathieu Desnoyers wrote:
> > Dunno, it seemed like a good a place as any.
> 
> My personal coding-style is to put all definitions
> at the top of C files, but I don't know if it's within
> the kernel coding style guide lines or just something
> I'm personally used to. I have no strong opinion here.

So I had all the data structure definition in the C file as well to keep
them private, and then you get into the situation where you can't put it
at the top anyhow.

I further wanted to keep the entire mod_tree stuff together so it can be
easily read. I suppose I can move it to the top of that section, but the
reason I had it there is that it didn't need to exist before that.

> > @@ -269,8 +275,15 @@ struct module {
> >  	/* Startup function. */
> >  	int (*init)(void);
> >  
> > +	/*
> > +	 * If this is non-NULL, vfree after init() returns
> > +	 *
> > +	 * cacheline align here, such that:
> > +	 *   module_init, module_core, init_size, core_size and
> > +	 *   tree_node[0]
> > +	 * are on the same cacheline.
> 
> Fat-fingered newline ? ;)

I made it:

        /*
         * If this is non-NULL, vfree after init() returns.
         *
         * Cacheline align here, such that:
         *   module_init, module_core, init_size, core_size,
         *   init_text_size, core_text_size and tree_node[0]
         * are on the same cacheline.
         */

To be consistent with the other comment.

> > +	 */
> > +	void *module_init	____cacheline_aligned;
> >  
> >  	/* Here is the actual code + data, vfree'd on unload. */
> >  	void *module_core;
> > @@ -281,6 +294,8 @@ struct module {
> >  	/* The size of the executable code in each section.  */
> >  	unsigned int init_text_size, core_text_size;
> >  
> > +	struct module_node tree_node[4];
> 
> 4 -> nr_module_addr_latch

Yeah, I dunno, that means moving that enum to the header file, I kinda
liked having it all together in the C file.

What Rusty want though.
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