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cpus: Fix throttling during vm_stop

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Throttling thread sleeps in VCPU thread. For high throttle percentage
this sleep is more than 10ms. E.g. for 60% - 15ms, for 99% - 990ms.
vm_stop() kicks all VCPUs and waits for them. It's called at the end of
migration and because of the long sleep the migration downtime might be
more than 100ms even for downtime-limit 1ms.
Use qemu_cond_timedwait for high percentage to wake up during vm_stop.

Signed-off-by: Yury Kotov <yury-kotov@yandex-team.ru>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190909131335.16848-3-yury-kotov@yandex-team.ru>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Yury Kotov 2019-09-09 16:13:34 +03:00 committed by Paolo Bonzini
parent 3dcc9c6ec4
commit bd1f7ff4b2
1 changed files with 17 additions and 8 deletions
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25
cpus.c
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@ -77,6 +77,8 @@
#endif /* CONFIG_LINUX */ #endif /* CONFIG_LINUX */
static QemuMutex qemu_global_mutex;
int64_t max_delay; int64_t max_delay;
int64_t max_advance; int64_t max_advance;
@ -782,7 +784,7 @@ static void cpu_throttle_thread(CPUState *cpu, run_on_cpu_data opaque)
{ {
double pct; double pct;
double throttle_ratio; double throttle_ratio;
long sleeptime_ns; int64_t sleeptime_ns, endtime_ns;
if (!cpu_throttle_get_percentage()) { if (!cpu_throttle_get_percentage()) {
return; return;
@ -790,11 +792,20 @@ static void cpu_throttle_thread(CPUState *cpu, run_on_cpu_data opaque)
pct = (double)cpu_throttle_get_percentage()/100; pct = (double)cpu_throttle_get_percentage()/100;
throttle_ratio = pct / (1 - pct); throttle_ratio = pct / (1 - pct);
sleeptime_ns = (long)(throttle_ratio * CPU_THROTTLE_TIMESLICE_NS); /* Add 1ns to fix double's rounding error (like 0.9999999...) */
sleeptime_ns = (int64_t)(throttle_ratio * CPU_THROTTLE_TIMESLICE_NS + 1);
qemu_mutex_unlock_iothread(); endtime_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + sleeptime_ns;
g_usleep(sleeptime_ns / 1000); /* Convert ns to us for usleep call */ while (sleeptime_ns > 0 && !cpu->stop) {
qemu_mutex_lock_iothread(); if (sleeptime_ns > SCALE_MS) {
qemu_cond_timedwait(cpu->halt_cond, &qemu_global_mutex,
sleeptime_ns / SCALE_MS);
} else {
qemu_mutex_unlock_iothread();
g_usleep(sleeptime_ns / SCALE_US);
qemu_mutex_lock_iothread();
}
sleeptime_ns = endtime_ns - qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
}
atomic_set(&cpu->throttle_thread_scheduled, 0); atomic_set(&cpu->throttle_thread_scheduled, 0);
} }
@ -1172,8 +1183,6 @@ static void qemu_init_sigbus(void)
} }
#endif /* !CONFIG_LINUX */ #endif /* !CONFIG_LINUX */
static QemuMutex qemu_global_mutex;
static QemuThread io_thread; static QemuThread io_thread;
/* cpu creation */ /* cpu creation */