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authorEric Dumazet <dada1@cosmosbay.com>2008-01-03 20:41:28 -0800
committerDavid S. Miller <davem@davemloft.net>2008-01-28 15:00:35 -0800
commit571e7682026fd0e25833d103a3eeb74be29bf199 (patch)
tree3707c7fb4ea4384a163cddc9fac76e9d8860a109 /include/linux/pcounter.h
parent789675e216617b1331875c42a81f58227a06df91 (diff)
[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>
Diffstat (limited to 'include/linux/pcounter.h')
-rw-r--r--include/linux/pcounter.h80
1 files changed, 26 insertions, 54 deletions
diff --git a/include/linux/pcounter.h b/include/linux/pcounter.h
index 9c4760a328f..a82d9f2628c 100644
--- 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 */