[PATCH 03/23] lib: percpu_counter variable batch

Peter Zijlstra
2007-08-03T13:02:48Z

[-- Attachment #1: percpu_counter_batch.patch --]
[-- Type: text/plain, Size: 2503 bytes --]

Because the current batch setup has an quadric error bound on the counter,
allow for an alternative setup.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
include/linux/percpu_counter.h | 10 +++++++++-
lib/percpu_counter.c | 6 +++---
2 files changed, 12 insertions(+), 4 deletions(-)

Index: linux-2.6/include/linux/percpu_counter.h
===================================================================
--- linux-2.6.orig/include/linux/percpu_counter.h 2007-05-23 20:34:12.000000000 +0200
+++ linux-2.6/include/linux/percpu_counter.h 2007-05-23 20:36:06.000000000 +0200
@@ -32,9 +32,14 @@ struct percpu_counter {

void percpu_counter_init(struct percpu_counter *fbc, s64 amount);
void percpu_counter_destroy(struct percpu_counter *fbc);
-void percpu_counter_add(struct percpu_counter *fbc, s32 amount);
+void __percpu_counter_add(struct percpu_counter *fbc, s32 amount, s32 batch);
s64 percpu_counter_sum(struct percpu_counter *fbc);

+static inline void percpu_counter_add(struct percpu_counter *fbc, s32 amount)
+{
+ __percpu_counter_add(fbc, amount, FBC_BATCH);
+}
+
static inline s64 percpu_counter_read(struct percpu_counter *fbc)
{
return fbc->count;
@@ -70,6 +75,9 @@ static inline void percpu_counter_destro
{
}

+#define __percpu_counter_add(fbc, amount, batch) \
+ percpu_counter_add(fbc, amount)
+
static inline void
percpu_counter_add(struct percpu_counter *fbc, s32 amount)
{
Index: linux-2.6/lib/percpu_counter.c
===================================================================
--- linux-2.6.orig/lib/percpu_counter.c 2007-05-23 20:34:12.000000000 +0200
+++ linux-2.6/lib/percpu_counter.c 2007-05-23 20:36:21.000000000 +0200
@@ -14,7 +14,7 @@ static LIST_HEAD(percpu_counters);
static DEFINE_MUTEX(percpu_counters_lock);
#endif

-void percpu_counter_add(struct percpu_counter *fbc, s32 amount)
+void __percpu_counter_add(struct percpu_counter *fbc, s32 amount, s32 batch)
{
long count;
s32 *pcount;
@@ -22,7 +22,7 @@ void percpu_counter_add(struct percpu_co

pcount = per_cpu_ptr(fbc->counters, cpu);
count = *pcount + amount;
- if (count >= FBC_BATCH || count <= -FBC_BATCH) {
+ if (count >= batch || count <= -batch) {
spin_lock(&fbc->lock);
fbc->count += count;
*pcount = 0;
@@ -32,7 +32,7 @@ void percpu_counter_add(struct percpu_co
}
put_cpu();
}
-EXPORT_SYMBOL(percpu_counter_add);
+EXPORT_SYMBOL(__percpu_counter_add);

/*
* Add up all the per-cpu counts, return the result. This is a more accurate

--