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Re: [Qemu-devel] [RFC PATCH v4 07/25] icount: implement icount requestin
From: |
Pavel Dovgaluk |
Subject: |
Re: [Qemu-devel] [RFC PATCH v4 07/25] icount: implement icount requesting |
Date: |
Fri, 7 Nov 2014 14:36:08 +0300 |
> From: Paolo Bonzini [mailto:address@hidden
> On 07/11/2014 11:32, Pavel Dovgalyuk wrote:
> > Replay uses number of executed instructions to determine corrent events
> > injection moments. This patch introduces new function for querying the
> > instructions counter.
> >
> > Signed-off-by: Pavel Dovgalyuk <address@hidden>
> > ---
> > cpus.c | 26 +++++++++++++++++++++++---
> > include/qemu/timer.h | 1 +
> > 2 files changed, 24 insertions(+), 3 deletions(-)
> >
> > diff --git a/cpus.c b/cpus.c
> > index 7e8c507..2ec6d75 100644
> > --- a/cpus.c
> > +++ b/cpus.c
> > @@ -136,8 +136,7 @@ typedef struct TimersState {
> >
> > static TimersState timers_state;
> >
> > -/* Return the virtual CPU time, based on the instruction counter. */
> > -static int64_t cpu_get_icount_locked(void)
> > +static int64_t cpu_get_instructions_counter_locked(void)
> > {
> > int64_t icount;
> > CPUState *cpu = current_cpu;
> > @@ -145,10 +144,31 @@ static int64_t cpu_get_icount_locked(void)
> > icount = timers_state.qemu_icount;
> > if (cpu) {
> > if (!cpu_can_do_io(cpu)) {
> > - fprintf(stderr, "Bad clock read\n");
> > + fprintf(stderr, "Bad icount read\n");
> > + exit(1);
> > }
> > icount -= (cpu->icount_decr.u16.low + cpu->icount_extra);
> > }
> > + return icount;
> > +}
> > +
> > +int64_t cpu_get_instructions_counter(void)
> > +{
> > + /* This function calls are synchnonized to timer changes,
> > + calling cpu_get_instructions_counter_locked without lock is safe */
> > + int64_t icount = timers_state.qemu_icount;
> > + CPUState *cpu = current_cpu;
> > +
> > + if (cpu) {
> > + icount -= (cpu->icount_decr.u16.low + cpu->icount_extra);
> > + }
> > + return icount;
> > +}
>
> This is the same as Frederic's QEMU_CLOCK_ICOUNT clock, right? Any
> reason why one is better than the other?
Not really. Frederic's QEMU_CLOCK_ICOUNT is measured in nanoseconds.
And this counter is measured in instructions.
Pavel Dovgalyuk
- [Qemu-devel] [RFC PATCH v4 04/25] sysemu: system functions for replay, (continued)
[Qemu-devel] [RFC PATCH v4 08/25] icount: improve enable/disable ticks, Pavel Dovgalyuk, 2014/11/07
[Qemu-devel] [RFC PATCH v4 09/25] replay: introduce icount event, Pavel Dovgalyuk, 2014/11/07
[Qemu-devel] [RFC PATCH v4 10/25] i386: do not cross the pages boundaries in replay mode, Pavel Dovgalyuk, 2014/11/07
[Qemu-devel] [RFC PATCH v4 11/25] cpu-exec: allow temporary disabling icount, Pavel Dovgalyuk, 2014/11/07