cpu: Provide vcpu throttling interface

Provide a method to throttle guest cpu execution. CPUState is augmented with
timeout controls and throttle start/stop functions. To throttle the guest cpu
the caller simply has to call the throttle set function and provide a percentage
of throttle time.

Signed-off-by: Jason J. Herne <jjherne@linux.vnet.ibm.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.vnet.ibm.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Jason J. Herne 2015-09-08 13:12:33 -04:00 committed by Juan Quintela
parent 2a6e6e59df
commit 2adcc85d40
2 changed files with 120 additions and 0 deletions

78
cpus.c
View File

@ -69,6 +69,14 @@ static CPUState *next_cpu;
int64_t max_delay;
int64_t max_advance;
/* vcpu throttling controls */
static QEMUTimer *throttle_timer;
static unsigned int throttle_percentage;
#define CPU_THROTTLE_PCT_MIN 1
#define CPU_THROTTLE_PCT_MAX 99
#define CPU_THROTTLE_TIMESLICE_NS 10000000
bool cpu_is_stopped(CPUState *cpu)
{
return cpu->stopped || !runstate_is_running();
@ -505,10 +513,80 @@ static const VMStateDescription vmstate_timers = {
}
};
static void cpu_throttle_thread(void *opaque)
{
CPUState *cpu = opaque;
double pct;
double throttle_ratio;
long sleeptime_ns;
if (!cpu_throttle_get_percentage()) {
return;
}
pct = (double)cpu_throttle_get_percentage()/100;
throttle_ratio = pct / (1 - pct);
sleeptime_ns = (long)(throttle_ratio * CPU_THROTTLE_TIMESLICE_NS);
qemu_mutex_unlock_iothread();
atomic_set(&cpu->throttle_thread_scheduled, 0);
g_usleep(sleeptime_ns / 1000); /* Convert ns to us for usleep call */
qemu_mutex_lock_iothread();
}
static void cpu_throttle_timer_tick(void *opaque)
{
CPUState *cpu;
double pct;
/* Stop the timer if needed */
if (!cpu_throttle_get_percentage()) {
return;
}
CPU_FOREACH(cpu) {
if (!atomic_xchg(&cpu->throttle_thread_scheduled, 1)) {
async_run_on_cpu(cpu, cpu_throttle_thread, cpu);
}
}
pct = (double)cpu_throttle_get_percentage()/100;
timer_mod(throttle_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT) +
CPU_THROTTLE_TIMESLICE_NS / (1-pct));
}
void cpu_throttle_set(int new_throttle_pct)
{
/* Ensure throttle percentage is within valid range */
new_throttle_pct = MIN(new_throttle_pct, CPU_THROTTLE_PCT_MAX);
new_throttle_pct = MAX(new_throttle_pct, CPU_THROTTLE_PCT_MIN);
atomic_set(&throttle_percentage, new_throttle_pct);
timer_mod(throttle_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT) +
CPU_THROTTLE_TIMESLICE_NS);
}
void cpu_throttle_stop(void)
{
atomic_set(&throttle_percentage, 0);
}
bool cpu_throttle_active(void)
{
return (cpu_throttle_get_percentage() != 0);
}
int cpu_throttle_get_percentage(void)
{
return atomic_read(&throttle_percentage);
}
void cpu_ticks_init(void)
{
seqlock_init(&timers_state.vm_clock_seqlock, NULL);
vmstate_register(NULL, 0, &vmstate_timers, &timers_state);
throttle_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL_RT,
cpu_throttle_timer_tick, NULL);
}
void configure_icount(QemuOpts *opts, Error **errp)

View File

@ -321,6 +321,11 @@ struct CPUState {
uint32_t can_do_io;
int32_t exception_index; /* used by m68k TCG */
/* Used to keep track of an outstanding cpu throttle thread for migration
* autoconverge
*/
bool throttle_thread_scheduled;
/* Note that this is accessed at the start of every TB via a negative
offset from AREG0. Leave this field at the end so as to make the
(absolute value) offset as small as possible. This reduces code
@ -565,6 +570,43 @@ CPUState *qemu_get_cpu(int index);
*/
bool cpu_exists(int64_t id);
/**
* cpu_throttle_set:
* @new_throttle_pct: Percent of sleep time. Valid range is 1 to 99.
*
* Throttles all vcpus by forcing them to sleep for the given percentage of
* time. A throttle_percentage of 25 corresponds to a 75% duty cycle roughly.
* (example: 10ms sleep for every 30ms awake).
*
* cpu_throttle_set can be called as needed to adjust new_throttle_pct.
* Once the throttling starts, it will remain in effect until cpu_throttle_stop
* is called.
*/
void cpu_throttle_set(int new_throttle_pct);
/**
* cpu_throttle_stop:
*
* Stops the vcpu throttling started by cpu_throttle_set.
*/
void cpu_throttle_stop(void);
/**
* cpu_throttle_active:
*
* Returns: %true if the vcpus are currently being throttled, %false otherwise.
*/
bool cpu_throttle_active(void);
/**
* cpu_throttle_get_percentage:
*
* Returns the vcpu throttle percentage. See cpu_throttle_set for details.
*
* Returns: The throttle percentage in range 1 to 99.
*/
int cpu_throttle_get_percentage(void);
#ifndef CONFIG_USER_ONLY
typedef void (*CPUInterruptHandler)(CPUState *, int);