The algorithm used was defined on the list while discussing the new IO accounting overhaul. See http://lists.nongnu.org/archive/html/qemu-devel/2014-08/msg04954.html
Signed-off-by: Benoît Canet <benoit.ca...@nodalink.com> --- include/qemu/timed-average.h | 45 +++++++++++++++++++ tests/Makefile | 2 + tests/test-timed-average.c | 53 ++++++++++++++++++++++ util/Makefile.objs | 1 + util/timed-average.c | 102 +++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 203 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..abe583a --- /dev/null +++ b/include/qemu/timed-average.h @@ -0,0 +1,45 @@ +/* + * 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 or + * (at your option) version 3 of the License. + * + * 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 TimedAverage { + uint64_t sum; /* sum of the discrete values */ + uint64_t count; /* number of values */ + uint64_t period; /* period in seconds */ + int64_t expiration; /* the end of the current period slice in ns */ + 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_get(TimedAverage *ta); + +#endif diff --git a/tests/Makefile b/tests/Makefile index 469c0a5..9b51b32 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 libqemustub.a 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..170b394 --- /dev/null +++ b/tests/test-timed-average.c @@ -0,0 +1,53 @@ +/* + * 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 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; + + /* we will compute some average on a period of 1 second */ + timed_average_init(&ta, QEMU_CLOCK_HOST, 1); + account(&ta); + result = timed_average_get(&ta); + g_assert(result == 3); + + /* sleep a while so the current slice expires */ + sleep(1); + + /* recompute the same average */ + account(&ta); + result = timed_average_get(&ta); + g_assert(result == 3); +} +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..2e687a5 --- /dev/null +++ b/util/timed-average.c @@ -0,0 +1,102 @@ +/* + * 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 or + * (at your option) version 3 of the License. + * + * 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 seconds + */ + +/* Set the expiration of the ta->periods seconds time slice + * + * @ta: the timed average structure used + */ +static void timed_average_set_expiration(TimedAverage *ta) +{ + int64_t period = ta->period * NANOSECONDS_PER_SECOND; + int64_t now = qemu_clock_get_ns(ta->clock_type); + ta->expiration = ROUND_UP(now + 1, period); +} + +/* Check if the ta->periods seconds time slice has expired + * + * If the slice has expired the counters will be reseted + * + * @ta: the timed average structure used + */ +static void timed_average_check_expiration(TimedAverage *ta) +{ + int64_t now = qemu_clock_get_ns(ta->clock_type); + + /* if we are still in the period slice do nothing */ + if (now < ta->expiration) { + return; + } + + /* the slice has expired -> create a new slice */ + ta->sum = 0; + ta->count = 0; + timed_average_set_expiration(ta); +} + +/* Initialize a TimedAverage structure + * + * @ta: the timed average structure used + * @clock_type: the type of clock to use + * @period: the time slice period in seconds + */ +void timed_average_init(TimedAverage *ta, QEMUClockType clock_type, + uint64_t period) +{ + memset(ta, 0, sizeof(TimedAverage)); + ta->clock_type = clock_type; + ta->period = period; + timed_average_set_expiration(ta); +} + +/* Account a value in the average + * + * @ta: the timed average structure used + * @value: the value to account in the average + */ +void timed_average_account(TimedAverage *ta, uint64_t value) +{ + timed_average_check_expiration(ta); + ta->sum += value; + ta->count++; +} + +/* Get the resulting average value + * + * @ta: the timed average structure used + */ +uint64_t timed_average_get(TimedAverage *ta) +{ + timed_average_check_expiration(ta); + + if (ta->count) { + return ta->sum / ta->count; + } + + return 0; +} -- 2.1.0
