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Date: Wed, 7 Nov 2007 14:16:15 -0200
From: "Arnaldo Carvalho de Melo" <acme@...hat.com>
To: "David S. Miller" <davem@...emloft.net>
Cc: dada1@...mosbay.com, netdev@...r.kernel.org
Subject: [PATCH 1/2] [LIB]: Introduce struct pcounter
This just generalises what was introduced by Eric Dumazet for the struct proto
inuse field in 286ab3d46058840d68e5d7d52e316c1f7e98c59f:
[NET]: Define infrastructure to keep 'inuse' changes in an efficent SMP/NUMA way.
Please look at the comment in there to see the rationale.
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
include/linux/pcounter.h | 102 ++++++++++++++++++++++++++++++++++++++++++++++
lib/Makefile | 1 +
lib/pcounter.c | 26 ++++++++++++
3 files changed, 129 insertions(+), 0 deletions(-)
create mode 100644 include/linux/pcounter.h
create mode 100644 lib/pcounter.c
diff --git a/include/linux/pcounter.h b/include/linux/pcounter.h
new file mode 100644
index 0000000..3d3891b
--- /dev/null
+++ b/include/linux/pcounter.h
@@ -0,0 +1,102 @@
+#ifndef __LINUX_PCOUNTER_H
+#define __LINUX_PCOUNTER_H
+
+struct pcounter {
+#ifdef CONFIG_SMP
+ void (*add)(struct pcounter *self, int inc);
+ int (*getval)(const struct pcounter *self);
+ 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 PCOUNTER_MEMBER_INITIALIZER(NAME, MEMBER) \
+ MEMBER = { \
+ .add = NAME##_pcounter_add, \
+ .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);
+}
+
+#else /* CONFIG_SMP */
+
+static inline void pcounter_add(struct pcounter *self, int inc)
+{
+ self->value += inc;
+}
+
+static inline int pcounter_getval(const struct pcounter *self)
+{
+ return self->val;
+}
+
+#define DEFINE_PCOUNTER(NAME)
+#define PCOUNTER_MEMBER_INITIALIZER(NAME, MEMBER)
+#define pcounter_alloc(self) 0
+#define pcounter_free(self)
+
+#endif /* CONFIG_SMP */
+
+#endif /* __LINUX_PCOUNTER_H */
diff --git a/lib/Makefile b/lib/Makefile
index 3a0983b..0fe94ec 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -61,6 +61,7 @@ obj-$(CONFIG_TEXTSEARCH_KMP) += ts_kmp.o
obj-$(CONFIG_TEXTSEARCH_BM) += ts_bm.o
obj-$(CONFIG_TEXTSEARCH_FSM) += ts_fsm.o
obj-$(CONFIG_SMP) += percpu_counter.o
+obj-$(CONFIG_SMP) += pcounter.o
obj-$(CONFIG_AUDIT_GENERIC) += audit.o
obj-$(CONFIG_SWIOTLB) += swiotlb.o
diff --git a/lib/pcounter.c b/lib/pcounter.c
new file mode 100644
index 0000000..e89880e
--- /dev/null
+++ b/lib/pcounter.c
@@ -0,0 +1,26 @@
+/*
+ * Define default pcounter functions
+ * Note that often used pcounters use dedicated functions to get a speed increase.
+ * (see DEFINE_PCOUNTER/REF_PCOUNTER_MEMBER)
+ */
+
+#include <linux/module.h>
+#include <linux/pcounter.h>
+#include <linux/smp.h>
+
+void pcounter_def_add(struct pcounter *self, int inc)
+{
+ per_cpu_ptr(self->per_cpu_values, smp_processor_id())[0] += inc;
+}
+
+EXPORT_SYMBOL_GPL(pcounter_def_add);
+
+int pcounter_def_getval(const struct pcounter *self)
+{
+ int res = 0, cpu;
+ for_each_possible_cpu(cpu)
+ res += per_cpu_ptr(self->per_cpu_values, cpu)[0];
+ return res;
+}
+
+EXPORT_SYMBOL_GPL(pcounter_def_getval);
--
1.5.3.4
-
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