mars/lib_limiter.c

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// (c) 2012 Thomas Schoebel-Theuer / 1&1 Internet AG
#include "lib_limiter.h"
#include <linux/kernel.h>
#include <linux/module.h>
int mars_limit(struct mars_limiter *lim, int amount)
{
int delay = 0;
long long now;
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now = cpu_clock(raw_smp_processor_id());
/* Compute the maximum delay along the path
* down to the root of the hierarchy tree.
*/
while (lim != NULL) {
if (likely(lim->lim_stamp)) {
long long elapsed = now - lim->lim_stamp;
int rate;
/* Races are possible, but taken into account.
* There is no real harm from rarely lost updates.
*/
if (likely(amount > 0))
lim->lim_accu += amount;
rate = (long long)lim->lim_accu * LIMITER_TIME_RESOLUTION / elapsed;
lim->lim_rate = rate;
// limit exceeded?
if (lim->lim_max_rate > 0 && rate > lim->lim_max_rate) {
int this_delay = 1000 - (long long)lim->lim_max_rate * 1000 / rate;
// compute maximum
if (this_delay > delay)
delay = this_delay;
}
elapsed -= LIMITER_TIME_RESOLUTION * 2;
if (elapsed > LIMITER_TIME_RESOLUTION) {
lim->lim_stamp += elapsed;
if (lim->lim_accu > 0) {
lim->lim_accu -= (long long)lim->lim_max_rate * elapsed / LIMITER_TIME_RESOLUTION;
}
}
} else {
if (unlikely(amount < 0))
amount = 0;
lim->lim_accu = amount;
lim->lim_stamp = now;
lim->lim_rate = 0;
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}
lim = lim->lim_father;
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}
return delay;
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}
EXPORT_SYMBOL_GPL(mars_limit);