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lib: percpu_counter variable batch

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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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Peter Zijlstra 2007-10-16 23:25:43 -07:00 committed by Linus Torvalds
parent 3cb4f9fa0c
commit 252e0ba6b7
2 changed files with 12 additions and 4 deletions
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10
include/linux/percpu_counter.h
View file

@ -32,9 +32,14 @@ struct percpu_counter {
void percpu_counter_init(struct percpu_counter *fbc, s64 amount); void percpu_counter_init(struct percpu_counter *fbc, s64 amount);
void percpu_counter_destroy(struct percpu_counter *fbc); 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); 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) static inline s64 percpu_counter_read(struct percpu_counter *fbc)
{ {
return fbc->count; return fbc->count;
@ -70,6 +75,9 @@ static inline void percpu_counter_destroy(struct percpu_counter *fbc)
{ {
} }
#define __percpu_counter_add(fbc, amount, batch) \
percpu_counter_add(fbc, amount)
static inline void static inline void
percpu_counter_add(struct percpu_counter *fbc, s32 amount) percpu_counter_add(struct percpu_counter *fbc, s32 amount)
{ {

6
lib/percpu_counter.c
View file

@ -14,7 +14,7 @@ static LIST_HEAD(percpu_counters);
static DEFINE_MUTEX(percpu_counters_lock); static DEFINE_MUTEX(percpu_counters_lock);
#endif #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; long count;
s32 *pcount; s32 *pcount;
@ -22,7 +22,7 @@ void percpu_counter_add(struct percpu_counter *fbc, s32 amount)
pcount = per_cpu_ptr(fbc->counters, cpu); pcount = per_cpu_ptr(fbc->counters, cpu);
count = *pcount + amount; count = *pcount + amount;
if (count >= FBC_BATCH || count <= -FBC_BATCH) { if (count >= batch || count <= -batch) {
spin_lock(&fbc->lock); spin_lock(&fbc->lock);
fbc->count += count; fbc->count += count;
*pcount = 0; *pcount = 0;
@ -32,7 +32,7 @@ void percpu_counter_add(struct percpu_counter *fbc, s32 amount)
} }
put_cpu(); 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 * Add up all the per-cpu counts, return the result. This is a more accurate