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Commit 252e0ba6 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Linus Torvalds
Browse files

lib: percpu_counter variable batch 



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

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3cb4f9fa

include/linux/percpu_counter.h

+9 −1
Original line number Diff line number Diff line
@@ -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_destroy(struct percpu_counter *fbc) 
{

}



#define __percpu_counter_add(fbc, amount, batch) \

	percpu_counter_add(fbc, amount)



static inline void

percpu_counter_add(struct percpu_counter *fbc, s32 amount)

{

lib/percpu_counter.c

+3 −3
Original line number Diff line number Diff line
@@ -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_counter *fbc, s32 amount) 


	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_counter *fbc, s32 amount) 
	}

	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