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"
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#include "lamport.h"
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#include <linux/kernel.h>
#include <linux/module.h>
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/* For precisions, _internal_ time is in multiples of the following basic time units */
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#define LIMITER_TIME_RESOLUTION NSEC_PER_SEC
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#define DEFAULT_MIN_WINDOW (LIMITER_TIME_RESOLUTION * 1)
#define DEFAULT_MAX_WINDOW (LIMITER_TIME_RESOLUTION * 4)
#define MAX_DIVIDER (DEFAULT_MIN_WINDOW / 10)
#define MS_TO_TR(x) ((__s64)(x) * (LIMITER_TIME_RESOLUTION / 1000))
#define TR_TO_MS(x) ((x) / (LIMITER_TIME_RESOLUTION / 1000))
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int mars_limit(struct mars_limiter *lim, int amount)
{
int delay = 0;
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struct lamport_time now;
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if (unlikely(amount < 0))
amount = 0;
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now = get_real_lamport();
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/* Compute the maximum delay along the path
* down to the root of the hierarchy tree.
*/
while (lim != NULL) {
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struct lamport_time diff = lamport_time_sub(now, lim->lim_stamp);
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__s64 window = lamport_time_to_ns(&diff);
__s64 rate_raw;
int rate;
int max_rate;
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/* Sometimes, raw CPU clocks may do weired things...
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* Small windows in the denominator could fake unrealistic rates.
* Do not divide by too small numbers.
*/
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if (window < MAX_DIVIDER)
window = MAX_DIVIDER;
if (unlikely(lim->lim_min_window_ms <= TR_TO_MS(MAX_DIVIDER)))
lim->lim_min_window_ms = TR_TO_MS(DEFAULT_MIN_WINDOW);
if (unlikely(lim->lim_max_window_ms <= lim->lim_min_window_ms))
lim->lim_max_window_ms = lim->lim_min_window_ms + TR_TO_MS(DEFAULT_MAX_WINDOW);
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/* Update total statistics.
* They will intentionally wrap around.
* Userspace must take care of that.
*/
if (likely(amount > 0)) {
lim->lim_total_amount += amount;
lim->lim_total_ops++;
}
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/* Only use incremental accumulation at repeated calls, but
* never after longer pauses.
*/
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if (!lim->lim_stamp.tv_sec ||
window > MS_TO_TR(lim->lim_max_window_ms)) {
/* reset, start over with new measurement cycle */
memset(&diff, 0, sizeof(diff));
lim->lim_stamp = now;
lim->lim_ops_accu = 0;
lim->lim_amount_accu = 0;
lim->lim_ops_rate = 0;
lim->lim_amount_rate = 0;
window = MAX_DIVIDER;
} else {
__s64 diff_window;
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/* Try to keep the window between min_window and 2 * min_window.
* We wait until min_window has been exceeded _twice_,
* and then reduce the window by only 1 * min_window.
*/
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diff_window = window - MS_TO_TR(lim->lim_min_window_ms);
if (diff_window > MS_TO_TR(lim->lim_min_window_ms)) {
__s64 used_up;
__s64 add_window = 0;
used_up = lim->lim_amount_accu * diff_window / window;
if (used_up > 0) {
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add_window = diff_window;
lim->lim_amount_accu -= used_up;
if (unlikely(lim->lim_amount_accu < 0))
lim->lim_amount_accu = 0;
}
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used_up = lim->lim_ops_accu * diff_window / window;
if (used_up > 0) {
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if (diff_window > add_window)
add_window = diff_window;
lim->lim_ops_accu -= used_up;
if (unlikely(lim->lim_ops_accu < 0))
lim->lim_ops_accu = 0;
}
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if (add_window > 0) {
lamport_time_add_ns(&lim->lim_stamp, add_window);
/* recompute the new window */
diff = lamport_time_sub(now, lim->lim_stamp);
window = lamport_time_to_ns(&diff);
}
}
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}
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/* Races are possible, but taken into account.
* There is no real harm from rarely lost updates.
*/
if (likely(amount > 0)) {
lim->lim_amount_accu += amount;
lim->lim_ops_accu++;
}
/* compute amount values */
rate_raw = lim->lim_amount_accu * LIMITER_TIME_RESOLUTION / window;
rate = rate_raw;
if (unlikely(rate_raw > INT_MAX)) {
rate = INT_MAX;
}
lim->lim_amount_rate = rate;
/* amount limit exceeded? */
max_rate = lim->lim_max_amount_rate;
if (max_rate > 0 && rate > max_rate) {
int this_delay = (window * rate / max_rate - window);
// compute maximum
if (this_delay > delay && this_delay > 0)
delay = this_delay;
}
/* compute ops values */
rate_raw = lim->lim_ops_accu * LIMITER_TIME_RESOLUTION / window;
rate = rate_raw;
if (unlikely(rate_raw > INT_MAX)) {
rate = INT_MAX;
}
lim->lim_ops_rate = rate;
/* ops limit exceeded? */
max_rate = lim->lim_max_ops_rate;
if (max_rate > 0 && rate > max_rate) {
int this_delay = (window * rate / max_rate - window);
// compute maximum
if (this_delay > delay && this_delay > 0)
delay = this_delay;
}
lim = lim->lim_father;
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}
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return TR_TO_MS(delay);
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}
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void mars_limit_sleep(struct mars_limiter *lim, int amount)
{
int sleep = mars_limit(lim, amount);
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if (sleep > 0) {
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if (unlikely(lim->lim_max_delay_ms <= 0))
lim->lim_max_delay_ms = 1000;
if (sleep > lim->lim_max_delay_ms)
sleep = lim->lim_max_delay_ms;
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brick_msleep(sleep);
}
}
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void mars_limit_reset(struct mars_limiter *lim)
{
if (!lim)
return;
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memset(&lim->lim_stamp, 0, sizeof(lim->lim_stamp));
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mars_limit(lim, 0);
}