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Subject[PATCH] module: reorder struct module to save space on 64 bit builds
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reorder struct module to save space on 64 bit builds.
saves 1 cacheline_size (128 on default x86_64 & 64 on AMD
Opteron/athlon) when CONFIG_MODULE_UNLOAD=y.

Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
---

Patch against 2.6.26-rc6. tested & running successfully on AMD64 desktop
machine. This patch reduces the data segment of each module by 1
cacheline size.

I also compiled with this patch for 32 bit & there was no change in
size.

Richard




diff --git a/include/linux/module.h b/include/linux/module.h
index 3e03b1a..63f0eb6 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -249,27 +249,28 @@ struct module

/* Exported symbols */
const struct kernel_symbol *syms;
- unsigned int num_syms;
const unsigned long *crcs;
+ unsigned int num_syms;

/* GPL-only exported symbols. */
- const struct kernel_symbol *gpl_syms;
unsigned int num_gpl_syms;
+ const struct kernel_symbol *gpl_syms;
const unsigned long *gpl_crcs;

/* unused exported symbols. */
const struct kernel_symbol *unused_syms;
- unsigned int num_unused_syms;
const unsigned long *unused_crcs;
+ unsigned int num_unused_syms;
+
/* GPL-only, unused exported symbols. */
- const struct kernel_symbol *unused_gpl_syms;
unsigned int num_unused_gpl_syms;
+ const struct kernel_symbol *unused_gpl_syms;
const unsigned long *unused_gpl_crcs;

/* symbols that will be GPL-only in the near future. */
const struct kernel_symbol *gpl_future_syms;
- unsigned int num_gpl_future_syms;
const unsigned long *gpl_future_crcs;
+ unsigned int num_gpl_future_syms;

/* Exception table */
unsigned int num_exentries;
@@ -300,23 +301,9 @@ struct module

#ifdef CONFIG_GENERIC_BUG
/* Support for BUG */
+ unsigned num_bugs;
struct list_head bug_list;
struct bug_entry *bug_table;
- unsigned num_bugs;
-#endif
-
-#ifdef CONFIG_MODULE_UNLOAD
- /* Reference counts */
- struct module_ref ref[NR_CPUS];
-
- /* What modules depend on me? */
- struct list_head modules_which_use_me;
-
- /* Who is waiting for us to be unloaded */
- struct task_struct *waiter;
-
- /* Destruction function. */
- void (*exit)(void);
#endif

#ifdef CONFIG_KALLSYMS
@@ -342,6 +329,21 @@ struct module
struct marker *markers;
unsigned int num_markers;
#endif
+
+#ifdef CONFIG_MODULE_UNLOAD
+ /* What modules depend on me? */
+ struct list_head modules_which_use_me;
+
+ /* Who is waiting for us to be unloaded */
+ struct task_struct *waiter;
+
+ /* Destruction function. */
+ void (*exit)(void);
+
+ /* Reference counts */
+ struct module_ref ref[NR_CPUS];
+#endif
+
};
#ifndef MODULE_ARCH_INIT
#define MODULE_ARCH_INIT {}



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