module: Optimize __module_address() using a latched RB-tree
Currently __module_address() is using a linear search through all
modules in order to find the module corresponding to the provided
address. With a lot of modules this can take a lot of time.
One of the users of this is kernel_text_address() which is employed
in many stack unwinders; which in turn are used by perf-callchain and
ftrace (possibly from NMI context).
So by optimizing __module_address() we optimize many stack unwinders
which are used by both perf and tracing in performance sensitive code.
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/include/linux/module.h b/include/linux/module.h
index fb56dd8..ddf35a3 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -17,6 +17,7 @@
#include <linux/moduleparam.h>
#include <linux/jump_label.h>
#include <linux/export.h>
+#include <linux/rbtree_latch.h>
#include <linux/percpu.h>
#include <asm/module.h>
@@ -210,6 +211,13 @@
MODULE_STATE_UNFORMED, /* Still setting it up. */
};
+struct module;
+
+struct mod_tree_node {
+ struct module *mod;
+ struct latch_tree_node node;
+};
+
struct module {
enum module_state state;
@@ -269,8 +277,15 @@
/* Startup function. */
int (*init)(void);
- /* If this is non-NULL, vfree after init() returns */
- void *module_init;
+ /*
+ * 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 ltn_core.node[0]
+ * are on the same cacheline.
+ */
+ void *module_init ____cacheline_aligned;
/* Here is the actual code + data, vfree'd on unload. */
void *module_core;
@@ -281,6 +296,14 @@
/* The size of the executable code in each section. */
unsigned int init_text_size, core_text_size;
+ /*
+ * We want mtn_core::{mod,node[0]} to be in the same cacheline as the
+ * above entries such that a regular lookup will only touch one
+ * cacheline.
+ */
+ struct mod_tree_node mtn_core;
+ struct mod_tree_node mtn_init;
+
/* Size of RO sections of the module (text+rodata) */
unsigned int init_ro_size, core_ro_size;
@@ -367,7 +390,7 @@
ctor_fn_t *ctors;
unsigned int num_ctors;
#endif
-};
+} ____cacheline_aligned;
#ifndef MODULE_ARCH_INIT
#define MODULE_ARCH_INIT {}
#endif