mars/kernel/lib_limiter.c

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/*
* MARS Long Distance Replication Software
*
* This file is part of MARS project: http://schoebel.github.io/mars/
*
* Copyright (C) 2010-2014 Thomas Schoebel-Theuer
* Copyright (C) 2011-2014 1&1 Internet AG
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
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#include "lib_limiter.h"
#include <linux/kernel.h>
#include <linux/module.h>
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#define LIMITER_TIME_RESOLUTION NSEC_PER_SEC
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int mars_limit(struct mars_limiter *lim, int amount)
{
int delay = 0;
long long now;
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if (unlikely(amount < 0))
amount = 0;
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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) {
long long window = now - lim->lim_stamp;
/* Sometimes, raw CPU clocks may do weired things...
* Smaller windows in the denominator than 1s could fake unrealistic rates.
*/
if (unlikely(lim->lim_min_window <= 0))
lim->lim_min_window = 1000;
if (unlikely(lim->lim_max_window <= lim->lim_min_window))
lim->lim_max_window = lim->lim_min_window + 8000;
if (unlikely(window < (long long)lim->lim_min_window * (LIMITER_TIME_RESOLUTION / 1000)))
window = (long long)lim->lim_min_window * (LIMITER_TIME_RESOLUTION / 1000);
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/* Update total statistics.
* They will intentionally wrap around.
* Userspace must take care of that.
*/
lim->lim_total_ops++;
lim->lim_total_sum += amount;
/* Only use incremental accumulation at repeated calls, but
* never after longer pauses.
*/
if (likely(lim->lim_stamp &&
window < (long long)lim->lim_max_window * (LIMITER_TIME_RESOLUTION / 1000))) {
long long rate_raw;
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;
lim->lim_cumul += amount;
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lim->lim_count++;
}
rate_raw = lim->lim_accu * LIMITER_TIME_RESOLUTION / window;
rate = rate_raw;
if (unlikely(rate_raw > INT_MAX)) {
rate = INT_MAX;
}
lim->lim_rate = rate;
// limit exceeded?
if (lim->lim_max_rate > 0 && rate > lim->lim_max_rate) {
int this_delay = (window * rate / lim->lim_max_rate - window) / (LIMITER_TIME_RESOLUTION / 1000);
// compute maximum
if (this_delay > delay && this_delay > 0)
delay = this_delay;
}
/* Try to keep the next window below min_window
*/
window -= lim->lim_min_window * (LIMITER_TIME_RESOLUTION / 1000);
if (window > 0) {
long long used_up = (long long)lim->lim_rate * window / LIMITER_TIME_RESOLUTION;
if (used_up > 0) {
lim->lim_stamp += window;
lim->lim_accu -= used_up;
if (unlikely(lim->lim_accu < 0))
lim->lim_accu = 0;
}
}
} else { // reset, start over with new measurement cycle
lim->lim_accu = amount;
lim->lim_stamp = now - lim->lim_min_window * (LIMITER_TIME_RESOLUTION / 1000);
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);
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void mars_limit_sleep(struct mars_limiter *lim, int amount)
{
int sleep = mars_limit(lim, amount);
if (sleep > 0) {
if (unlikely(lim->lim_max_delay <= 0))
lim->lim_max_delay = 1000;
if (sleep > lim->lim_max_delay)
sleep = lim->lim_max_delay;
brick_msleep(sleep);
}
}
EXPORT_SYMBOL_GPL(mars_limit_sleep);
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void mars_limit_reset(struct mars_limiter *lim)
{
if (!lim)
return;
lim->lim_stamp = 0;
mars_limit(lim, 0);
}