The module takes care of computing minimal and maximal values over the time slice duration.
Suggested-by: Paolo Bonzini <pbonz...@redhat.com> Signed-off-by: Benoît Canet <benoit.ca...@nodalink.com> --- include/qemu/timed-average.h | 60 +++++++++++++ tests/Makefile | 2 + tests/test-timed-average.c | 89 ++++++++++++++++++ util/Makefile.objs | 1 + util/timed-average.c | 208 +++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 360 insertions(+) create mode 100644 include/qemu/timed-average.h create mode 100644 tests/test-timed-average.c create mode 100644 util/timed-average.c diff --git a/include/qemu/timed-average.h b/include/qemu/timed-average.h new file mode 100644 index 0000000..8150ead --- /dev/null +++ b/include/qemu/timed-average.h @@ -0,0 +1,60 @@ +/* + * QEMU timed average computation + * + * Copyright (C) Nodalink, EURL. 2014 + * + * Author: + * Benoît Canet <benoit.ca...@nodalink.com> + * + * 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) 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/>. + */ + +#ifndef TIMED_AVERAGE_H +#define TIMED_AVERAGE_H + +#include <stdint.h> + +#include "qemu/timer.h" + +typedef struct Window { + uint64_t min; /* minimal value accounted in the window */ + uint64_t max; /* maximal value accounted in the window */ + uint64_t sum; /* sum of the discrete values */ + uint64_t count; /* number of values */ + int64_t expiration; /* the end of the current window in ns */ +} Window; + +typedef struct TimedAverage { + Window windows[2]; /* two overlapping windows of period + * nanoseconds with an offset of period / 2 + * between them + */ + + uint64_t period; /* period in nanoseconds */ + uint64_t current; /* the current window index: it's also the + * oldest window index + */ + QEMUClockType clock_type; /* the clock used */ +} TimedAverage; + +void timed_average_init(TimedAverage *ta, QEMUClockType clock_type, + uint64_t period); + +void timed_average_account(TimedAverage *ta, uint64_t value); + +uint64_t timed_average_min(TimedAverage *ta); +uint64_t timed_average_avg(TimedAverage *ta); +uint64_t timed_average_max(TimedAverage *ta); + +#endif diff --git a/tests/Makefile b/tests/Makefile index 469c0a5..d3669f4 100644 --- a/tests/Makefile +++ b/tests/Makefile @@ -64,6 +64,7 @@ gcov-files-check-qom-interface-y = qom/object.c check-unit-$(CONFIG_POSIX) += tests/test-vmstate$(EXESUF) check-unit-y += tests/test-qemu-opts$(EXESUF) gcov-files-test-qemu-opts-y = qom/test-qemu-opts.c +check-unit-y += tests/test-timed-average$(EXESUF) check-block-$(CONFIG_POSIX) += tests/qemu-iotests-quick.sh @@ -259,6 +260,7 @@ tests/test-qdev-global-props$(EXESUF): tests/test-qdev-global-props.o \ tests/test-vmstate$(EXESUF): tests/test-vmstate.o \ vmstate.o qemu-file.o \ libqemuutil.a +tests/test-timed-average$(EXESUF): tests/test-timed-average.o qemu-timer.o libqemuutil.a stubs/clock-warp.o stubs/cpu-get-icount.o stubs/notify-event.o tests/test-qapi-types.c tests/test-qapi-types.h :\ $(SRC_PATH)/tests/qapi-schema/qapi-schema-test.json $(SRC_PATH)/scripts/qapi-types.py diff --git a/tests/test-timed-average.c b/tests/test-timed-average.c new file mode 100644 index 0000000..5091589 --- /dev/null +++ b/tests/test-timed-average.c @@ -0,0 +1,89 @@ +/* + * Timed average computation tests + * + * Copyright Nodalink, EURL. 2014 + * + * Authors: + * Benoît Canet <benoit.ca...@nodalink.com> + * + * This work is licensed under the terms of the GNU LGPL, version 2 or later. + * See the COPYING.LIB file in the top-level directory. + */ + +#include <glib.h> +#include <unistd.h> + +#include "qemu/timed-average.h" + +static int64_t my_clock_value; + +int64_t cpu_get_clock(void) +{ + return my_clock_value; +} + +static void account(TimedAverage *ta) +{ + timed_average_account(ta, 1); + timed_average_account(ta, 5); + timed_average_account(ta, 2); + timed_average_account(ta, 4); + timed_average_account(ta, 3); +} + +static void test_average(void) +{ + TimedAverage ta; + uint64_t result; + int i; + + /* we will compute some average on a period of 1 second */ + timed_average_init(&ta, QEMU_CLOCK_VIRTUAL, 1); + + result = timed_average_min(&ta); + g_assert(result == 0); + result = timed_average_avg(&ta); + g_assert(result == 0); + result = timed_average_max(&ta); + g_assert(result == 0); + + for (i = 0; i < 100; i++) { + account(&ta); + result = timed_average_min(&ta); + g_assert(result == 1); + result = timed_average_avg(&ta); + g_assert(result == 3); + result = timed_average_max(&ta); + g_assert(result == 5); + my_clock_value += NANOSECONDS_PER_SECOND / 10; + } + + my_clock_value += (int64_t) NANOSECONDS_PER_SECOND * 100; + + result = timed_average_min(&ta); + g_assert(result == 0); + result = timed_average_avg(&ta); + g_assert(result == 0); + result = timed_average_max(&ta); + g_assert(result == 0); + + for (i = 0; i < 100; i++) { + account(&ta); + result = timed_average_min(&ta); + g_assert(result == 1); + result = timed_average_avg(&ta); + g_assert(result == 3); + result = timed_average_max(&ta); + g_assert(result == 5); + my_clock_value += NANOSECONDS_PER_SECOND / 10; + } +} + +int main(int argc, char **argv) +{ + /* tests in the same order as the header function declarations */ + g_test_init(&argc, &argv, NULL); + g_test_add_func("/timed-average/average", test_average); + return g_test_run(); +} + diff --git a/util/Makefile.objs b/util/Makefile.objs index 6b3c83b..97d82ce 100644 --- a/util/Makefile.objs +++ b/util/Makefile.objs @@ -15,3 +15,4 @@ util-obj-y += throttle.o util-obj-y += getauxval.o util-obj-y += readline.o util-obj-y += rfifolock.o +util-obj-y += timed-average.o diff --git a/util/timed-average.c b/util/timed-average.c new file mode 100644 index 0000000..e594d37 --- /dev/null +++ b/util/timed-average.c @@ -0,0 +1,208 @@ +/* + * QEMU timed average computation + * + * Copyright (C) Nodalink, EURL. 2014 + * + * Author: + * Benoît Canet <benoit.ca...@nodalink.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 <string.h> + +#include "qemu/timed-average.h" + +/* This module compute an average on a time slice of ta->period nanoseconds + * + * Algorithm: + * + * - create two windows, with the suggested expiration period, and offsetted by + * period / 2 then return min/avg/max 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 ta->period nanoseconds time window + * + * @w: the window used + * @now: the current time in nanoseconds + * @period: the expiration period in nanoseconds + */ +static void update_expiration(Window *w, int64_t now, int64_t period) +{ + /* time delta elapsed since last theorical expiration */ + int64_t delta = (now - w->expiration) % period; + /* time remaininging until next theorical expiration */ + int64_t remaining = period - delta; + /* compute expiration */ + w->expiration = now + remaining; +} + +/* Reset a window + * + * @w: the window to reset + */ +static void window_reset(Window *w) +{ + w->min = UINT64_MAX; + w->max = 0; + w->sum = 0; + w->count = 0; +} + +/* Get the current window + * + * @ta: the TimedAverage we are working with + * @ret: a pointer to the current window + */ +static Window *current_window(TimedAverage *ta) +{ + return &ta->windows[ta->current % 2]; +} + +/* Check if one or the two ta->period nanoseconds time window have expired + * + * If a window has expired its counters will be reset and its expiration time + * updated + * + * @ta: the timed average structure used + */ +static void check_expirations(TimedAverage *ta) +{ + int64_t now = qemu_clock_get_ns(ta->clock_type); + int i; + + /* check that both window are not expired + * if a window is expired reset it and update it's expiration time + */ + for (i = 0; i < 2; i++) { + Window *w = current_window(ta); + if (now < w->expiration) { + continue; + } + window_reset(w); + update_expiration(w, now, ta->period); + ta->current++; + } +} + +/* initialize a TimedAverage structure + * + * @ta: the timed average structure used + * @clock_type: the type of clock to use + * @period: the time window period in seconds + */ +void timed_average_init(TimedAverage *ta, QEMUClockType clock_type, + uint64_t period) +{ + int64_t now = qemu_clock_get_ns(clock_type); + + /* reset the struct content */ + memset(ta, 0, sizeof(TimedAverage)); + + ta->period = period * NANOSECONDS_PER_SECOND; + ta->clock_type = clock_type; + + window_reset(&ta->windows[0]); + window_reset(&ta->windows[1]); + + /* first window expiration offsetted by an half period */ + ta->windows[0].expiration = now + ta->period / 2; + ta->windows[1].expiration = now + ta->period; +} + +/* Account a value + * + * @ta: the timed average structure used + * @value: the value to account in the average + */ +void timed_average_account(TimedAverage *ta, uint64_t value) +{ + int i; + check_expirations(ta); + + /* do the accouting in the two windows at the same time */ + for (i = 0; i < 2; i++) { + Window *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 minimal value + * + * @ta: the timed average structure used + * @ret: the minimal value + */ +uint64_t timed_average_min(TimedAverage *ta) +{ + Window *w; + check_expirations(ta); + + w = current_window(ta); + + if (w->min == UINT64_MAX) { + return 0; + } + + return w->min; +} + +/* Get the average value + * + * @ta: the timed average structure used + * @ret: the average value + */ +uint64_t timed_average_avg(TimedAverage *ta) +{ + Window *w; + check_expirations(ta); + + w = current_window(ta); + + if (w->count) { + return w->sum / w->count; + } + + return 0; +} + +/* Get the maximum value + * + * @ta: the timed average structure used + * @ret: the maximal value + */ +uint64_t timed_average_max(TimedAverage *ta) +{ + check_expirations(ta); + return current_window(ta)->max; +} -- 2.1.1
