Hi,
19.08.2019, 20:11, "Paolo Bonzini" <pbonz...@redhat.com>:
> On 19/08/19 18:39, Paolo Bonzini wrote:
>> On 15/08/19 11:13, Yury Kotov wrote:
>>> Ping ping
>>
>> Hi,
>>
>> sorry for the delay, I was waiting for the 4.1 release.
>>
>> I would like to make a small change so that preemption of QEMU does not
>> result in overly long sleeps. The following patch on top of yours computes
>> the throttle-end time just once. Of course you can still be unlucky if
>> you are preempted at the wrong time, but the window becomes much smaller.
Thanks for your suggestion! I'll use it in the v5.
>
> The new unit test is hanging for me on aarch64-softmmu.
>
Ok, I'll try to fix it in v5.
> Paolo
>
>> diff --git a/cpus.c b/cpus.c
>> index d091dbd..d7e2145 100644
>> --- a/cpus.c
>> +++ b/cpus.c
>> @@ -781,7 +781,7 @@ static void cpu_throttle_thread(CPUState *cpu,
>> run_on_cpu_data opaque)
>> {
>> double pct;
>> double throttle_ratio;
>> - int64_t sleeptime_ns;
>> + int64_t sleeptime_ns, end;
>>
>> if (!cpu_throttle_get_percentage()) {
>> return;
>> @@ -792,18 +792,17 @@ static void cpu_throttle_thread(CPUState *cpu,
>> run_on_cpu_data opaque)
>> /* Add 1ns to fix double's rounding error (like 0.9999999...) */
>> sleeptime_ns = (int64_t)(throttle_ratio * CPU_THROTTLE_TIMESLICE_NS +
>> 1);
>>
>> - while (sleeptime_ns >= SCALE_MS && !cpu->stop) {
>> - int64_t start, end;
>> - start = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
>> - qemu_cond_timedwait(cpu->halt_cond, &qemu_global_mutex,
>> - sleeptime_ns / SCALE_MS);
>> - end = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
>> - sleeptime_ns -= end - start;
>> - }
>> - if (sleeptime_ns >= SCALE_US && !cpu->stop) {
>> - qemu_mutex_unlock_iothread();
>> - g_usleep(sleeptime_ns / SCALE_US);
>> - qemu_mutex_lock_iothread();
>> + end = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + sleeptime_ns;
>> + while (sleeptime_ns > 0 && !cpu->stop) {
>> + 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 = end - qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
>> }
>> atomic_set(&cpu->throttle_thread_scheduled, 0);
>> }
Regards,
Yury
