Re: [Qemu-devel] [RFC PATCH v3 29/30] replay: improve replay performance
> From: Paolo Bonzini [mailto:pbonz...@redhat.com]
> On 12/01/2018 07:13, Pavel Dovgalyuk wrote:
> >> From: Paolo Bonzini [mailto:pbonz...@redhat.com]
> >> On 11/01/2018 14:12, Pavel Dovgalyuk wrote:
> From: Paolo Bonzini [mailto:paolo.bonz...@gmail.com] On Behalf Of Paolo
> Bonzini
> On 11/01/2018 09:27, Pavel Dovgalyuk wrote:
> > +} else {
> > +qemu_notify_event();
> > +}
>
> Before this patch, what would do the qemu_notify_event?
> >>>
> >>> We tried using qemu_notify_event to wake up the iothread and speedup the
> >>> replay,
> >>> when there is no work for vcpu thread to do.
> >>
> >> But why doesn't the iothread wake up on its own?
> >
> > It will wake up by timeout. But with this change this happens sooner and
> > replay goes faster.
>
> If you want replays to ignore timeouts, that should be done by ensuring
> that qemu-timer.c passes a zero timeout to main-loop.c. (It probably
> should be optional, too, maybe via -icount sleep).
Making it optional is a good one.
I'll exclude this patch from the series for working on it later.
Pavel Dovgalyuk
Re: [Qemu-devel] [RFC PATCH v3 29/30] replay: improve replay performance
On 12/01/2018 07:13, Pavel Dovgalyuk wrote:
>> From: Paolo Bonzini [mailto:pbonz...@redhat.com]
>> On 11/01/2018 14:12, Pavel Dovgalyuk wrote:
From: Paolo Bonzini [mailto:paolo.bonz...@gmail.com] On Behalf Of Paolo
Bonzini
On 11/01/2018 09:27, Pavel Dovgalyuk wrote:
> +} else {
> +qemu_notify_event();
> +}
Before this patch, what would do the qemu_notify_event?
>>>
>>> We tried using qemu_notify_event to wake up the iothread and speedup the
>>> replay,
>>> when there is no work for vcpu thread to do.
>>
>> But why doesn't the iothread wake up on its own?
>
> It will wake up by timeout. But with this change this happens sooner and
> replay goes faster.
If you want replays to ignore timeouts, that should be done by ensuring
that qemu-timer.c passes a zero timeout to main-loop.c. (It probably
should be optional, too, maybe via -icount sleep).
Paolo
Re: [Qemu-devel] [RFC PATCH v3 29/30] replay: improve replay performance
> From: Paolo Bonzini [mailto:pbonz...@redhat.com]
> On 11/01/2018 14:12, Pavel Dovgalyuk wrote:
> >> From: Paolo Bonzini [mailto:paolo.bonz...@gmail.com] On Behalf Of Paolo
> >> Bonzini
> >> On 11/01/2018 09:27, Pavel Dovgalyuk wrote:
> >>> +} else {
> >>> +qemu_notify_event();
> >>> +}
> >>
> >> Before this patch, what would do the qemu_notify_event?
> >
> > We tried using qemu_notify_event to wake up the iothread and speedup the
> > replay,
> > when there is no work for vcpu thread to do.
>
> But why doesn't the iothread wake up on its own?
It will wake up by timeout. But with this change this happens sooner and replay
goes faster.
Pavel Dovgalyuk
Re: [Qemu-devel] [RFC PATCH v3 29/30] replay: improve replay performance
On 11/01/2018 14:12, Pavel Dovgalyuk wrote:
>> From: Paolo Bonzini [mailto:paolo.bonz...@gmail.com] On Behalf Of Paolo
>> Bonzini
>> On 11/01/2018 09:27, Pavel Dovgalyuk wrote:
>>> +} else {
>>> +qemu_notify_event();
>>> +}
>>
>> Before this patch, what would do the qemu_notify_event?
>
> We tried using qemu_notify_event to wake up the iothread and speedup the
> replay,
> when there is no work for vcpu thread to do.
But why doesn't the iothread wake up on its own?
Paolo
Re: [Qemu-devel] [RFC PATCH v3 29/30] replay: improve replay performance
> From: Paolo Bonzini [mailto:paolo.bonz...@gmail.com] On Behalf Of Paolo
> Bonzini
> On 11/01/2018 09:27, Pavel Dovgalyuk wrote:
> > +} else {
> > +qemu_notify_event();
> > +}
>
> Before this patch, what would do the qemu_notify_event?
We tried using qemu_notify_event to wake up the iothread and speedup the replay,
when there is no work for vcpu thread to do.
Pavel Dovgalyuk
Re: [Qemu-devel] [RFC PATCH v3 29/30] replay: improve replay performance
On 11/01/2018 09:27, Pavel Dovgalyuk wrote:
> +} else {
> +qemu_notify_event();
> +}
Before this patch, what would do the qemu_notify_event?
Thanks,
Paolo
> /* Does not need atomic_mb_set because a spurious wakeup is okay. */
[Qemu-devel] [RFC PATCH v3 29/30] replay: improve replay performance
This patch skips cpu_exec when there is no CPU code to execute in replay mode.
Signed-off-by: Pavel Dovgalyuk
Signed-off-by: Maria Klimushenkova
---
cpus.c | 50 +--
include/sysemu/replay.h |3 +++
replay/replay.c | 13
3 files changed, 43 insertions(+), 23 deletions(-)
diff --git a/cpus.c b/cpus.c
index bafedfc..ef4c5b9 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1449,39 +1449,43 @@ static void *qemu_tcg_rr_cpu_thread_fn(void *arg)
cpu = first_cpu;
}
-while (cpu && !cpu->queued_work_first && !cpu->exit_request) {
+if (!replay_has_checkpoint()) {
+while (cpu && !cpu->queued_work_first && !cpu->exit_request) {
-atomic_mb_set(&tcg_current_rr_cpu, cpu);
-current_cpu = cpu;
+atomic_mb_set(&tcg_current_rr_cpu, cpu);
+current_cpu = cpu;
-qemu_clock_enable(QEMU_CLOCK_VIRTUAL,
- (cpu->singlestep_enabled & SSTEP_NOTIMER) == 0);
+qemu_clock_enable(QEMU_CLOCK_VIRTUAL,
+ (cpu->singlestep_enabled & SSTEP_NOTIMER) ==
0);
-if (cpu_can_run(cpu)) {
-int r;
+if (cpu_can_run(cpu)) {
+int r;
-prepare_icount_for_run(cpu);
+prepare_icount_for_run(cpu);
-r = tcg_cpu_exec(cpu);
+r = tcg_cpu_exec(cpu);
-process_icount_data(cpu);
+process_icount_data(cpu);
-if (r == EXCP_DEBUG) {
-cpu_handle_guest_debug(cpu);
-break;
-} else if (r == EXCP_ATOMIC) {
-cpu_exec_step_atomic(cpu);
+if (r == EXCP_DEBUG) {
+cpu_handle_guest_debug(cpu);
+break;
+} else if (r == EXCP_ATOMIC) {
+cpu_exec_step_atomic(cpu);
+break;
+}
+} else if (cpu->stop) {
+if (cpu->unplug) {
+cpu = CPU_NEXT(cpu);
+}
break;
}
-} else if (cpu->stop) {
-if (cpu->unplug) {
-cpu = CPU_NEXT(cpu);
-}
-break;
-}
-cpu = CPU_NEXT(cpu);
-} /* while (cpu && !cpu->exit_request).. */
+cpu = CPU_NEXT(cpu);
+} /* while (cpu && !cpu->exit_request).. */
+} else {
+qemu_notify_event();
+}
/* Does not need atomic_mb_set because a spurious wakeup is okay. */
atomic_set(&tcg_current_rr_cpu, NULL);
diff --git a/include/sysemu/replay.h b/include/sysemu/replay.h
index d026b28..44c1ff7 100644
--- a/include/sysemu/replay.h
+++ b/include/sysemu/replay.h
@@ -122,6 +122,9 @@ void replay_shutdown_request(ShutdownCause cause);
Returns 0 in PLAY mode if checkpoint was not found.
Returns 1 in all other cases. */
bool replay_checkpoint(ReplayCheckpoint checkpoint);
+/*! Used to determine that checkpoint is pending.
+Does not proceed to the next event in the log. */
+bool replay_has_checkpoint(void);
/* Asynchronous events queue */
diff --git a/replay/replay.c b/replay/replay.c
index c9fd984..b9c496a 100644
--- a/replay/replay.c
+++ b/replay/replay.c
@@ -219,6 +219,19 @@ out:
return res;
}
+bool replay_has_checkpoint(void)
+{
+bool res = false;
+if (replay_mode == REPLAY_MODE_PLAY) {
+replay_mutex_lock();
+replay_account_executed_instructions();
+res = EVENT_CHECKPOINT <= replay_state.data_kind
+&& replay_state.data_kind <= EVENT_CHECKPOINT_LAST;
+replay_mutex_unlock();
+}
+return res;
+}
+
void replay_init_locks(void)
{
replay_mutex_init();
