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Commit e2bab3d9 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds
Browse files

[PATCH] percpu_counter_sum() 



Implement percpu_counter_sum().  This is a more accurate but slower version of
percpu_counter_read_positive().

We need this for Alex's speedup-ext3_statfs patch and for the nr_file
accounting fix.  Otherwise these things would be too inaccurate on large CPU
counts.

Cc: Ravikiran G Thirumalai <kiran@scalex86.org>
Cc: Alex Tomas <alex@clusterfs.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent b884e257

include/linux/percpu_counter.h

+6 −0
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ static inline void percpu_counter_destroy(struct percpu_counter *fbc) 
}



void percpu_counter_mod(struct percpu_counter *fbc, long amount);

long percpu_counter_sum(struct percpu_counter *fbc);



static inline long percpu_counter_read(struct percpu_counter *fbc)

{
@@ -92,6 +93,11 @@ static inline long percpu_counter_read_positive(struct percpu_counter *fbc) 
	return fbc->count;

}



static inline long percpu_counter_sum(struct percpu_counter *fbc)

{

	return percpu_counter_read_positive(fbc);

}



#endif	/* CONFIG_SMP */



static inline void percpu_counter_inc(struct percpu_counter *fbc)

mm/swap.c

+23 −2
Original line number Diff line number Diff line
@@ -489,13 +489,34 @@ void percpu_counter_mod(struct percpu_counter *fbc, long amount) 
	if (count >= FBC_BATCH || count <= -FBC_BATCH) {

		spin_lock(&fbc->lock);

		fbc->count += count;

		*pcount = 0;

		spin_unlock(&fbc->lock);

		count = 0;

	}

	} else {

		*pcount = count;

	}

	put_cpu();

}

EXPORT_SYMBOL(percpu_counter_mod);



/*

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

 * but much slower version of percpu_counter_read_positive()

 */

long percpu_counter_sum(struct percpu_counter *fbc)

{

	long ret;

	int cpu;



	spin_lock(&fbc->lock);

	ret = fbc->count;

	for_each_cpu(cpu) {

		long *pcount = per_cpu_ptr(fbc->counters, cpu);

		ret += *pcount;

	}

	spin_unlock(&fbc->lock);

	return ret < 0 ? 0 : ret;

}

EXPORT_SYMBOL(percpu_counter_sum);

#endif



/*