Hello,
On Wed, Apr 13, 2011 at 03:22:36PM -0500, Christoph Lameter wrote:
> + do {
> + count = this_cpu_read(*fbc->counters);
> +
> + new = count + amount;
> + /* In case of overflow fold it into the global counter instead */
> + if (new >= batch || new <= -batch) {
> + spin_lock(&fbc->lock);
> + fbc->count += __this_cpu_read(*fbc->counters) + amount;
> + spin_unlock(&fbc->lock);
> + amount = 0;
> + new = 0;
> + }
> +
> + } while (this_cpu_cmpxchg(*fbc->counters, count, new) != count);
Is this correct? If the percpu count changes in the middle, doesn't
the count get added twice? Can you please use the cmpxchg() only in
the fast path? ie.
do {
count = this_cpu_read();
if (overflow) {
disable preemption and do the slow thing.
return;
}
} while (this_cpu_cmpxchg());
Thanks.
--
tejun
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxxx For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>