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-rw-r--r--qemu/util/timed-average.c231
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diff --git a/qemu/util/timed-average.c b/qemu/util/timed-average.c
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-/*
- * QEMU timed average computation
- *
- * Copyright (C) Nodalink, EURL. 2014
- * Copyright (C) Igalia, S.L. 2015
- *
- * Authors:
- * Benoît Canet <benoit.canet@nodalink.com>
- * Alberto Garcia <berto@igalia.com>
- *
- * This program is free sofware: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Sofware Foundation, either version 2 of the License, or
- * (at your option) version 3 or 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, see <http://www.gnu.org/licenses/>.
- */
-
-#include "qemu/osdep.h"
-
-#include "qemu/timed-average.h"
-
-/* This module computes an average of a set of values within a time
- * window.
- *
- * Algorithm:
- *
- * - Create two windows with a certain expiration period, and
- * offsetted by period / 2.
- * - Each time you want to account a new value, do it in both windows.
- * - The minimum / maximum / average values are always returned from
- * the oldest window.
- *
- * Example:
- *
- * t=0 |t=0.5 |t=1 |t=1.5 |t=2
- * wnd0: [0,0.5)|wnd0: [0.5,1.5) | |wnd0: [1.5,2.5) |
- * wnd1: [0,1) | |wnd1: [1,2) | |
- *
- * Values are returned from:
- *
- * wnd0---------|wnd1------------|wnd0---------|wnd1-------------|
- */
-
-/* Update the expiration of a time window
- *
- * @w: the window used
- * @now: the current time in nanoseconds
- * @period: the expiration period in nanoseconds
- */
-static void update_expiration(TimedAverageWindow *w, int64_t now,
- int64_t period)
-{
- /* time elapsed since the last theoretical expiration */
- int64_t elapsed = (now - w->expiration) % period;
- /* time remaininging until the next expiration */
- int64_t remaining = period - elapsed;
- /* compute expiration */
- w->expiration = now + remaining;
-}
-
-/* Reset a window
- *
- * @w: the window to reset
- */
-static void window_reset(TimedAverageWindow *w)
-{
- w->min = UINT64_MAX;
- w->max = 0;
- w->sum = 0;
- w->count = 0;
-}
-
-/* Get the current window (that is, the one with the earliest
- * expiration time).
- *
- * @ta: the TimedAverage structure
- * @ret: a pointer to the current window
- */
-static TimedAverageWindow *current_window(TimedAverage *ta)
-{
- return &ta->windows[ta->current];
-}
-
-/* Initialize a TimedAverage structure
- *
- * @ta: the TimedAverage structure
- * @clock_type: the type of clock to use
- * @period: the time window period in nanoseconds
- */
-void timed_average_init(TimedAverage *ta, QEMUClockType clock_type,
- uint64_t period)
-{
- int64_t now = qemu_clock_get_ns(clock_type);
-
- /* Returned values are from the oldest window, so they belong to
- * the interval [ta->period/2,ta->period). By adjusting the
- * requested period by 4/3, we guarantee that they're in the
- * interval [2/3 period,4/3 period), closer to the requested
- * period on average */
- ta->period = (uint64_t) period * 4 / 3;
- ta->clock_type = clock_type;
- ta->current = 0;
-
- window_reset(&ta->windows[0]);
- window_reset(&ta->windows[1]);
-
- /* Both windows are offsetted by half a period */
- ta->windows[0].expiration = now + ta->period / 2;
- ta->windows[1].expiration = now + ta->period;
-}
-
-/* Check if the time windows have expired, updating their counters and
- * expiration time if that's the case.
- *
- * @ta: the TimedAverage structure
- * @elapsed: if non-NULL, the elapsed time (in ns) within the current
- * window will be stored here
- */
-static void check_expirations(TimedAverage *ta, uint64_t *elapsed)
-{
- int64_t now = qemu_clock_get_ns(ta->clock_type);
- int i;
-
- assert(ta->period != 0);
-
- /* Check if the windows have expired */
- for (i = 0; i < 2; i++) {
- TimedAverageWindow *w = &ta->windows[i];
- if (w->expiration <= now) {
- window_reset(w);
- update_expiration(w, now, ta->period);
- }
- }
-
- /* Make ta->current point to the oldest window */
- if (ta->windows[0].expiration < ta->windows[1].expiration) {
- ta->current = 0;
- } else {
- ta->current = 1;
- }
-
- /* Calculate the elapsed time within the current window */
- if (elapsed) {
- int64_t remaining = ta->windows[ta->current].expiration - now;
- *elapsed = ta->period - remaining;
- }
-}
-
-/* Account a value
- *
- * @ta: the TimedAverage structure
- * @value: the value to account
- */
-void timed_average_account(TimedAverage *ta, uint64_t value)
-{
- int i;
- check_expirations(ta, NULL);
-
- /* Do the accounting in both windows at the same time */
- for (i = 0; i < 2; i++) {
- TimedAverageWindow *w = &ta->windows[i];
-
- w->sum += value;
- w->count++;
-
- if (value < w->min) {
- w->min = value;
- }
-
- if (value > w->max) {
- w->max = value;
- }
- }
-}
-
-/* Get the minimum value
- *
- * @ta: the TimedAverage structure
- * @ret: the minimum value
- */
-uint64_t timed_average_min(TimedAverage *ta)
-{
- TimedAverageWindow *w;
- check_expirations(ta, NULL);
- w = current_window(ta);
- return w->min < UINT64_MAX ? w->min : 0;
-}
-
-/* Get the average value
- *
- * @ta: the TimedAverage structure
- * @ret: the average value
- */
-uint64_t timed_average_avg(TimedAverage *ta)
-{
- TimedAverageWindow *w;
- check_expirations(ta, NULL);
- w = current_window(ta);
- return w->count > 0 ? w->sum / w->count : 0;
-}
-
-/* Get the maximum value
- *
- * @ta: the TimedAverage structure
- * @ret: the maximum value
- */
-uint64_t timed_average_max(TimedAverage *ta)
-{
- check_expirations(ta, NULL);
- return current_window(ta)->max;
-}
-
-/* Get the sum of all accounted values
- * @ta: the TimedAverage structure
- * @elapsed: if non-NULL, the elapsed time (in ns) will be stored here
- * @ret: the sum of all accounted values
- */
-uint64_t timed_average_sum(TimedAverage *ta, uint64_t *elapsed)
-{
- TimedAverageWindow *w;
- check_expirations(ta, elapsed);
- w = current_window(ta);
- return w->sum;
-}