Re: [PATCH 3/4] module: use a structure to encapsulate layout.
From: Rusty Russell
Date: Mon Nov 09 2015 - 20:57:56 EST
Peter Zijlstra <peterz@xxxxxxxxxxxxx> writes:
> On Mon, Nov 09, 2015 at 02:53:56PM +1030, Rusty Russell wrote:
>> diff --git a/kernel/module.c b/kernel/module.c
>> index 14b224967e7b..a0a3d6d9d5e8 100644
>> --- a/kernel/module.c
>> +++ b/kernel/module.c
>> @@ -108,13 +108,6 @@ static LIST_HEAD(modules);
>> * Use a latched RB-tree for __module_address(); this allows us to use
>> * RCU-sched lookups of the address from any context.
>> - * Because modules have two address ranges: init and core, we need two
>> - * latch_tree_nodes entries. Therefore we need the back-pointer from
>> - * mod_tree_node.
> We still have the back-pointers, so removing all of that seems a little
Well, I thought about filling the hole with a "am_init" flag, and
putting the layouts in a  array, but seemed too cutesy.
>> - *
>> - * Because init ranges are short lived we mark them unlikely and have placed
>> - * them outside the critical cacheline in struct module.
> This information also isn't preserved.
Ah yeah, Intel still use 64-byte cachelines. Still, this comment covers
what we actually care about:
+/* Only touch one cacheline for common rbtree-for-core-layout case. */
+#define __module_layout_align ____cacheline_aligned
> Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
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