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softmmu/dirtylimit: Implement virtual CPU throttle

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Setup a negative feedback system when vCPU thread
handling KVM_EXIT_DIRTY_RING_FULL exit by introducing
throttle_us_per_full field in struct CPUState. Sleep
throttle_us_per_full microseconds to throttle vCPU
if dirtylimit is in service.

Signed-off-by: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
Reviewed-by: Peter Xu <peterx@redhat.com>
Message-Id: <977e808e03a1cef5151cae75984658b6821be618.1656177590.git.huangy81@chinatelecom.cn>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
This commit is contained in:
Hyman Huang(黄勇) 2022-06-26 01:38:35 +08:00 • committed by Dr. David Alan Gilbert
parent 4a06a7cc05
commit baa609832e
5 changed files with 338 additions and 1 deletions
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20
accel/kvm/kvm-all.c
View file

@ -45,6 +45,7 @@
#include "qemu/guest-random.h"
#include "sysemu/hw_accel.h"
#include "kvm-cpus.h"
#include "sysemu/dirtylimit.h"
#include "hw/boards.h"
#include "monitor/stats.h"
@ -477,6 +478,7 @@ int kvm_init_vcpu(CPUState *cpu, Error **errp)
cpu->kvm_state = s;
cpu->vcpu_dirty = true;
cpu->dirty_pages = 0;
cpu->throttle_us_per_full = 0;
mmap_size = kvm_ioctl(s, KVM_GET_VCPU_MMAP_SIZE, 0);
if (mmap_size < 0) {
@ -1470,6 +1472,11 @@ static void *kvm_dirty_ring_reaper_thread(void *data)
*/
sleep(1);
/* keep sleeping so that dirtylimit not be interfered by reaper */
if (dirtylimit_in_service()) {
continue;
}
trace_kvm_dirty_ring_reaper("wakeup");
r->reaper_state = KVM_DIRTY_RING_REAPER_REAPING;
@ -2975,8 +2982,19 @@ int kvm_cpu_exec(CPUState *cpu)
*/
trace_kvm_dirty_ring_full(cpu->cpu_index);
qemu_mutex_lock_iothread();
kvm_dirty_ring_reap(kvm_state, NULL);
/*
* We throttle vCPU by making it sleep once it exit from kernel
* due to dirty ring full. In the dirtylimit scenario, reaping
* all vCPUs after a single vCPU dirty ring get full result in
* the miss of sleep, so just reap the ring-fulled vCPU.
*/
if (dirtylimit_in_service()) {
kvm_dirty_ring_reap(kvm_state, cpu);
} else {
kvm_dirty_ring_reap(kvm_state, NULL);
}
qemu_mutex_unlock_iothread();
dirtylimit_vcpu_execute(cpu);
ret = 0;
break;
case KVM_EXIT_SYSTEM_EVENT: