linux-kernel - [PATCH] [RFC] remove (more or less) unnecessary cacheline_aligned from module

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Date:	Sun, 11 Jan 2009 22:18:41 -0500
From:	Kyle McMartin <kyle@...radead.org>
To:	linux-kernel@...r.kernel.org
Cc:	rusty@...tcorp.com.au
Subject: [PATCH] [RFC] remove (more or less) unnecessary cacheline_aligned
	from module_ref

On x86_64 systems with CONFIG_MAXSMP set, NR_CPUS is exploded to 4096
cpus. This cacheline_aligned attribute on the local_t in module_ref
results in struct module bloating to over 512KB in size on x86_64, which
tends to, er, add up. This results in insane disk usage on distro
kernel configs (1GB+ on Fedora.)

Killing cacheline_aligned reduces the size of struct module to somewhat
more sane levels.

Signed-off-by: Kyle McMartin <kyle@...hat.com>
---
I'll followup with a patch to make mod->ref dynamically allocated, but
that needs a bit more thinking because module_unload_init currently
doesn't have a failure path.

Of course, reducing NR_CPUS to something sane was an easy way to patch
over the problem.

diff --git a/include/linux/module.h b/include/linux/module.h
index 4f7ea12..32b0bda 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -222,7 +222,7 @@ void *__symbol_get_gpl(const char *symbol);
 struct module_ref
 {
 	local_t count;
-} ____cacheline_aligned;
+};

 enum module_state
 {
--
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