--- /dev/null
+/*
+ * QEMU throttling infrastructure
+ *
+ * Copyright (C) Nodalink, EURL. 2013-2014
+ * Copyright (C) Igalia, S.L. 2015
+ *
+ * Authors:
+ * Benoît Canet <benoit.canet@nodalink.com>
+ * Alberto Garcia <berto@igalia.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 "qemu/throttle.h"
+#include "qemu/timer.h"
+#include "block/aio.h"
+
+/* This function make a bucket leak
+ *
+ * @bkt: the bucket to make leak
+ * @delta_ns: the time delta
+ */
+void throttle_leak_bucket(LeakyBucket *bkt, int64_t delta_ns)
+{
+ double leak;
+
+ /* compute how much to leak */
+ leak = (bkt->avg * (double) delta_ns) / NANOSECONDS_PER_SECOND;
+
+ /* make the bucket leak */
+ bkt->level = MAX(bkt->level - leak, 0);
+}
+
+/* Calculate the time delta since last leak and make proportionals leaks
+ *
+ * @now: the current timestamp in ns
+ */
+static void throttle_do_leak(ThrottleState *ts, int64_t now)
+{
+ /* compute the time elapsed since the last leak */
+ int64_t delta_ns = now - ts->previous_leak;
+ int i;
+
+ ts->previous_leak = now;
+
+ if (delta_ns <= 0) {
+ return;
+ }
+
+ /* make each bucket leak */
+ for (i = 0; i < BUCKETS_COUNT; i++) {
+ throttle_leak_bucket(&ts->cfg.buckets[i], delta_ns);
+ }
+}
+
+/* do the real job of computing the time to wait
+ *
+ * @limit: the throttling limit
+ * @extra: the number of operation to delay
+ * @ret: the time to wait in ns
+ */
+static int64_t throttle_do_compute_wait(double limit, double extra)
+{
+ double wait = extra * NANOSECONDS_PER_SECOND;
+ wait /= limit;
+ return wait;
+}
+
+/* This function compute the wait time in ns that a leaky bucket should trigger
+ *
+ * @bkt: the leaky bucket we operate on
+ * @ret: the resulting wait time in ns or 0 if the operation can go through
+ */
+int64_t throttle_compute_wait(LeakyBucket *bkt)
+{
+ double extra; /* the number of extra units blocking the io */
+
+ if (!bkt->avg) {
+ return 0;
+ }
+
+ extra = bkt->level - bkt->max;
+
+ if (extra <= 0) {
+ return 0;
+ }
+
+ return throttle_do_compute_wait(bkt->avg, extra);
+}
+
+/* This function compute the time that must be waited while this IO
+ *
+ * @is_write: true if the current IO is a write, false if it's a read
+ * @ret: time to wait
+ */
+static int64_t throttle_compute_wait_for(ThrottleState *ts,
+ bool is_write)
+{
+ BucketType to_check[2][4] = { {THROTTLE_BPS_TOTAL,
+ THROTTLE_OPS_TOTAL,
+ THROTTLE_BPS_READ,
+ THROTTLE_OPS_READ},
+ {THROTTLE_BPS_TOTAL,
+ THROTTLE_OPS_TOTAL,
+ THROTTLE_BPS_WRITE,
+ THROTTLE_OPS_WRITE}, };
+ int64_t wait, max_wait = 0;
+ int i;
+
+ for (i = 0; i < 4; i++) {
+ BucketType index = to_check[is_write][i];
+ wait = throttle_compute_wait(&ts->cfg.buckets[index]);
+ if (wait > max_wait) {
+ max_wait = wait;
+ }
+ }
+
+ return max_wait;
+}
+
+/* compute the timer for this type of operation
+ *
+ * @is_write: the type of operation
+ * @now: the current clock timestamp
+ * @next_timestamp: the resulting timer
+ * @ret: true if a timer must be set
+ */
+bool throttle_compute_timer(ThrottleState *ts,
+ bool is_write,
+ int64_t now,
+ int64_t *next_timestamp)
+{
+ int64_t wait;
+
+ /* leak proportionally to the time elapsed */
+ throttle_do_leak(ts, now);
+
+ /* compute the wait time if any */
+ wait = throttle_compute_wait_for(ts, is_write);
+
+ /* if the code must wait compute when the next timer should fire */
+ if (wait) {
+ *next_timestamp = now + wait;
+ return true;
+ }
+
+ /* else no need to wait at all */
+ *next_timestamp = now;
+ return false;
+}
+
+/* Add timers to event loop */
+void throttle_timers_attach_aio_context(ThrottleTimers *tt,
+ AioContext *new_context)
+{
+ tt->timers[0] = aio_timer_new(new_context, tt->clock_type, SCALE_NS,
+ tt->read_timer_cb, tt->timer_opaque);
+ tt->timers[1] = aio_timer_new(new_context, tt->clock_type, SCALE_NS,
+ tt->write_timer_cb, tt->timer_opaque);
+}
+
+/* To be called first on the ThrottleState */
+void throttle_init(ThrottleState *ts)
+{
+ memset(ts, 0, sizeof(ThrottleState));
+}
+
+/* To be called first on the ThrottleTimers */
+void throttle_timers_init(ThrottleTimers *tt,
+ AioContext *aio_context,
+ QEMUClockType clock_type,
+ QEMUTimerCB *read_timer_cb,
+ QEMUTimerCB *write_timer_cb,
+ void *timer_opaque)
+{
+ memset(tt, 0, sizeof(ThrottleTimers));
+
+ tt->clock_type = clock_type;
+ tt->read_timer_cb = read_timer_cb;
+ tt->write_timer_cb = write_timer_cb;
+ tt->timer_opaque = timer_opaque;
+ throttle_timers_attach_aio_context(tt, aio_context);
+}
+
+/* destroy a timer */
+static void throttle_timer_destroy(QEMUTimer **timer)
+{
+ assert(*timer != NULL);
+
+ timer_del(*timer);
+ timer_free(*timer);
+ *timer = NULL;
+}
+
+/* Remove timers from event loop */
+void throttle_timers_detach_aio_context(ThrottleTimers *tt)
+{
+ int i;
+
+ for (i = 0; i < 2; i++) {
+ throttle_timer_destroy(&tt->timers[i]);
+ }
+}
+
+/* To be called last on the ThrottleTimers */
+void throttle_timers_destroy(ThrottleTimers *tt)
+{
+ throttle_timers_detach_aio_context(tt);
+}
+
+/* is any throttling timer configured */
+bool throttle_timers_are_initialized(ThrottleTimers *tt)
+{
+ if (tt->timers[0]) {
+ return true;
+ }
+
+ return false;
+}
+
+/* Does any throttling must be done
+ *
+ * @cfg: the throttling configuration to inspect
+ * @ret: true if throttling must be done else false
+ */
+bool throttle_enabled(ThrottleConfig *cfg)
+{
+ int i;
+
+ for (i = 0; i < BUCKETS_COUNT; i++) {
+ if (cfg->buckets[i].avg > 0) {
+ return true;
+ }
+ }
+
+ return false;
+}
+
+/* return true if any two throttling parameters conflicts
+ *
+ * @cfg: the throttling configuration to inspect
+ * @ret: true if any conflict detected else false
+ */
+bool throttle_conflicting(ThrottleConfig *cfg)
+{
+ bool bps_flag, ops_flag;
+ bool bps_max_flag, ops_max_flag;
+
+ bps_flag = cfg->buckets[THROTTLE_BPS_TOTAL].avg &&
+ (cfg->buckets[THROTTLE_BPS_READ].avg ||
+ cfg->buckets[THROTTLE_BPS_WRITE].avg);
+
+ ops_flag = cfg->buckets[THROTTLE_OPS_TOTAL].avg &&
+ (cfg->buckets[THROTTLE_OPS_READ].avg ||
+ cfg->buckets[THROTTLE_OPS_WRITE].avg);
+
+ bps_max_flag = cfg->buckets[THROTTLE_BPS_TOTAL].max &&
+ (cfg->buckets[THROTTLE_BPS_READ].max ||
+ cfg->buckets[THROTTLE_BPS_WRITE].max);
+
+ ops_max_flag = cfg->buckets[THROTTLE_OPS_TOTAL].max &&
+ (cfg->buckets[THROTTLE_OPS_READ].max ||
+ cfg->buckets[THROTTLE_OPS_WRITE].max);
+
+ return bps_flag || ops_flag || bps_max_flag || ops_max_flag;
+}
+
+/* check if a throttling configuration is valid
+ * @cfg: the throttling configuration to inspect
+ * @ret: true if valid else false
+ */
+bool throttle_is_valid(ThrottleConfig *cfg)
+{
+ bool invalid = false;
+ int i;
+
+ for (i = 0; i < BUCKETS_COUNT; i++) {
+ if (cfg->buckets[i].avg < 0) {
+ invalid = true;
+ }
+ }
+
+ for (i = 0; i < BUCKETS_COUNT; i++) {
+ if (cfg->buckets[i].max < 0) {
+ invalid = true;
+ }
+ }
+
+ return !invalid;
+}
+
+/* fix bucket parameters */
+static void throttle_fix_bucket(LeakyBucket *bkt)
+{
+ double min;
+
+ /* zero bucket level */
+ bkt->level = 0;
+
+ /* The following is done to cope with the Linux CFQ block scheduler
+ * which regroup reads and writes by block of 100ms in the guest.
+ * When they are two process one making reads and one making writes cfq
+ * make a pattern looking like the following:
+ * WWWWWWWWWWWRRRRRRRRRRRRRRWWWWWWWWWWWWWwRRRRRRRRRRRRRRRRR
+ * Having a max burst value of 100ms of the average will help smooth the
+ * throttling
+ */
+ min = bkt->avg / 10;
+ if (bkt->avg && !bkt->max) {
+ bkt->max = min;
+ }
+}
+
+/* take care of canceling a timer */
+static void throttle_cancel_timer(QEMUTimer *timer)
+{
+ assert(timer != NULL);
+
+ timer_del(timer);
+}
+
+/* Used to configure the throttle
+ *
+ * @ts: the throttle state we are working on
+ * @tt: the throttle timers we use in this aio context
+ * @cfg: the config to set
+ */
+void throttle_config(ThrottleState *ts,
+ ThrottleTimers *tt,
+ ThrottleConfig *cfg)
+{
+ int i;
+
+ ts->cfg = *cfg;
+
+ for (i = 0; i < BUCKETS_COUNT; i++) {
+ throttle_fix_bucket(&ts->cfg.buckets[i]);
+ }
+
+ ts->previous_leak = qemu_clock_get_ns(tt->clock_type);
+
+ for (i = 0; i < 2; i++) {
+ throttle_cancel_timer(tt->timers[i]);
+ }
+}
+
+/* used to get config
+ *
+ * @ts: the throttle state we are working on
+ * @cfg: the config to write
+ */
+void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg)
+{
+ *cfg = ts->cfg;
+}
+
+
+/* Schedule the read or write timer if needed
+ *
+ * NOTE: this function is not unit tested due to it's usage of timer_mod
+ *
+ * @tt: the timers structure
+ * @is_write: the type of operation (read/write)
+ * @ret: true if the timer has been scheduled else false
+ */
+bool throttle_schedule_timer(ThrottleState *ts,
+ ThrottleTimers *tt,
+ bool is_write)
+{
+ int64_t now = qemu_clock_get_ns(tt->clock_type);
+ int64_t next_timestamp;
+ bool must_wait;
+
+ must_wait = throttle_compute_timer(ts,
+ is_write,
+ now,
+ &next_timestamp);
+
+ /* request not throttled */
+ if (!must_wait) {
+ return false;
+ }
+
+ /* request throttled and timer pending -> do nothing */
+ if (timer_pending(tt->timers[is_write])) {
+ return true;
+ }
+
+ /* request throttled and timer not pending -> arm timer */
+ timer_mod(tt->timers[is_write], next_timestamp);
+ return true;
+}
+
+/* do the accounting for this operation
+ *
+ * @is_write: the type of operation (read/write)
+ * @size: the size of the operation
+ */
+void throttle_account(ThrottleState *ts, bool is_write, uint64_t size)
+{
+ double units = 1.0;
+
+ /* if cfg.op_size is defined and smaller than size we compute unit count */
+ if (ts->cfg.op_size && size > ts->cfg.op_size) {
+ units = (double) size / ts->cfg.op_size;
+ }
+
+ ts->cfg.buckets[THROTTLE_BPS_TOTAL].level += size;
+ ts->cfg.buckets[THROTTLE_OPS_TOTAL].level += units;
+
+ if (is_write) {
+ ts->cfg.buckets[THROTTLE_BPS_WRITE].level += size;
+ ts->cfg.buckets[THROTTLE_OPS_WRITE].level += units;
+ } else {
+ ts->cfg.buckets[THROTTLE_BPS_READ].level += size;
+ ts->cfg.buckets[THROTTLE_OPS_READ].level += units;
+ }
+}
+
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