[LIB] pcounter : unline too big functions

Before pushing pcounter to Linus tree, I would like to make some adjustments.

Goal is to reduce kernel text size, by unlining too big functions.

When a pcounter is bound to a statically defined per_cpu variable,
we define two small helpers functions. (No more folding function
using the fat for_each_possible_cpu(cpu) ... )

static DEFINE_PER_CPU(int, NAME##_pcounter_values);
static void NAME##_pcounter_add(struct pcounter *self, int val)
{
       __get_cpu_var(NAME##_pcounter_values) += val;
}
static int NAME##_pcounter_getval(const struct pcounter *self, int cpu)
{
       return per_cpu(NAME##_pcounter_values, cpu);
}

Fast path is therefore unchanged, while folding/alloc/free is now unlined.

This saves 228 bytes on i386

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/pcounter.h b/include/linux/pcounter.h
index 9c4760a328f32e43866a0dd7e524746a34eadadc..a82d9f2628ca2158e8dedc986aed37cb397fb0a9 100644 (file)
--- a/include/linux/pcounter.h
+++ b/include/linux/pcounter.h
@@ -1,41 +1,39 @@
 #ifndef __LINUX_PCOUNTER_H
 #define __LINUX_PCOUNTER_H
-
+/*
+ * Using a dynamic percpu 'int' variable has a cost :
+ * 1) Extra dereference
+ * Current per_cpu_ptr() implementation uses an array per 'percpu variable'.
+ * 2) memory cost of NR_CPUS*(32+sizeof(void *)) instead of num_possible_cpus()*4
+ *
+ * This pcounter implementation is an abstraction to be able to use
+ * either a static or a dynamic per cpu variable.
+ * One dynamic per cpu variable gets a fast & cheap implementation, we can
+ * change pcounter implementation too.
+ */
 struct pcounter {
 #ifdef CONFIG_SMP
        void            (*add)(struct pcounter *self, int inc);
-       int             (*getval)(const struct pcounter *self);
+       int             (*getval)(const struct pcounter *self, int cpu);
        int             *per_cpu_values;
 #else
        int             val;
 #endif
 };
 
-/*
- * Special macros to let pcounters use a fast version of {getvalue|add}
- * using a static percpu variable per pcounter instead of an allocated one,
- * saving one dereference.
- * This might be changed if/when dynamic percpu vars become fast.
- */
 #ifdef CONFIG_SMP
-#include <linux/cpumask.h>
 #include <linux/percpu.h>
 
-#define DEFINE_PCOUNTER(NAME)                                  \
-static DEFINE_PER_CPU(int, NAME##_pcounter_values);            \
-static void NAME##_pcounter_add(struct pcounter *self, int inc)        \
-{                                                              \
-       __get_cpu_var(NAME##_pcounter_values) += inc;           \
-}                                                              \
-                                                               \
-static int NAME##_pcounter_getval(const struct pcounter *self) \
-{                                                              \
-       int res = 0, cpu;                                       \
-                                                               \
-       for_each_possible_cpu(cpu)                              \
-               res += per_cpu(NAME##_pcounter_values, cpu);    \
-       return res;                                             \
-}
+#define DEFINE_PCOUNTER(NAME)                                          \
+static DEFINE_PER_CPU(int, NAME##_pcounter_values);                    \
+static void NAME##_pcounter_add(struct pcounter *self, int val)                \
+{                                                                      \
+       __get_cpu_var(NAME##_pcounter_values) += val;                   \
+}                                                                      \
+static int NAME##_pcounter_getval(const struct pcounter *self, int cpu)        \
+{                                                                      \
+       return per_cpu(NAME##_pcounter_values, cpu);                    \
+}                                                                      \
 
 #define PCOUNTER_MEMBER_INITIALIZER(NAME, MEMBER)              \
        MEMBER = {                                              \
@@ -43,42 +41,16 @@ static int NAME##_pcounter_getval(const struct pcounter *self)      \
                .getval = NAME##_pcounter_getval,               \
        }
 
-extern void pcounter_def_add(struct pcounter *self, int inc);
-extern int pcounter_def_getval(const struct pcounter *self);
-
-static inline int pcounter_alloc(struct pcounter *self)
-{
-       int rc = 0;
-       if (self->add == NULL) {
-               self->per_cpu_values = alloc_percpu(int);
-               if (self->per_cpu_values != NULL) {
-                       self->add    = pcounter_def_add;
-                       self->getval = pcounter_def_getval;
-               } else
-                       rc = 1;
-       }
-       return rc;
-}
-
-static inline void pcounter_free(struct pcounter *self)
-{
-       if (self->per_cpu_values != NULL) {
-               free_percpu(self->per_cpu_values);
-               self->per_cpu_values = NULL;
-               self->getval = NULL;
-               self->add = NULL;
-       }
-}
 
 static inline void pcounter_add(struct pcounter *self, int inc)
 {
        self->add(self, inc);
 }
 
-static inline int pcounter_getval(const struct pcounter *self)
-{
-       return self->getval(self);
-}
+extern int pcounter_getval(const struct pcounter *self);
+extern int pcounter_alloc(struct pcounter *self);
+extern void pcounter_free(struct pcounter *self);
+
 
 #else /* CONFIG_SMP */
 

diff --git a/lib/pcounter.c b/lib/pcounter.c
index 93feea598251ba0c7cc052241c15cdb59a59f7fd..9b56807da93b483bc91f6e0bfdcedc9854485ec6 100644 (file)
--- a/lib/pcounter.c
+++ b/lib/pcounter.c
@@ -7,20 +7,52 @@
 #include <linux/module.h>
 #include <linux/pcounter.h>
 #include <linux/smp.h>
+#include <linux/cpumask.h>
 
-void pcounter_def_add(struct pcounter *self, int inc)
+static void pcounter_dyn_add(struct pcounter *self, int inc)
 {
        per_cpu_ptr(self->per_cpu_values, smp_processor_id())[0] += inc;
 }
 
-EXPORT_SYMBOL_GPL(pcounter_def_add);
+static int pcounter_dyn_getval(const struct pcounter *self, int cpu)
+{
+       return per_cpu_ptr(self->per_cpu_values, cpu)[0];
+}
 
-int pcounter_def_getval(const struct pcounter *self)
+int pcounter_getval(const struct pcounter *self)
 {
        int res = 0, cpu;
+
        for_each_possible_cpu(cpu)
-               res += per_cpu_ptr(self->per_cpu_values, cpu)[0];
+               res += self->getval(self, cpu);
+
        return res;
 }
+EXPORT_SYMBOL_GPL(pcounter_getval);
+
+int pcounter_alloc(struct pcounter *self)
+{
+       int rc = 0;
+       if (self->add == NULL) {
+               self->per_cpu_values = alloc_percpu(int);
+               if (self->per_cpu_values != NULL) {
+                       self->add    = pcounter_dyn_add;
+                       self->getval = pcounter_dyn_getval;
+               } else
+                       rc = 1;
+       }
+       return rc;
+}
+EXPORT_SYMBOL_GPL(pcounter_alloc);
+
+void pcounter_free(struct pcounter *self)
+{
+       if (self->per_cpu_values != NULL) {
+               free_percpu(self->per_cpu_values);
+               self->per_cpu_values = NULL;
+               self->getval = NULL;
+               self->add = NULL;
+       }
+}
+EXPORT_SYMBOL_GPL(pcounter_free);
 
-EXPORT_SYMBOL_GPL(pcounter_def_getval);