On Sat, Nov 02, 2019 at 04:49:19PM +0100, Laurent Vivier wrote: > With the Quadra 800 emulation, mos6522 timers processing can consume > until 70% of the host CPU time with an idle guest (I guess the problem > should also happen with PowerMac emulation). > > On a recent system, it can be painless (except if you look at top), but > on an old host like a PowerMac G5 the guest kernel can be terribly slow > during the boot sequence (for instance, unpacking initramfs can take 15 > seconds rather than only 3 seconds). > > We can avoid this CPU overload by enabling QEMU internal timers only if > the mos6522 counter interrupts are enabled. Sometime the guest kernel > wants to read the counters values, but we don't need the timers to > update the counters. > > With this patch applied, an idle Q800 consumes only 3% of host CPU time > (and the guest can boot in a decent time). > > Signed-off-by: Laurent Vivier <laur...@vivier.eu>
Applied to ppc-for-4.2, thanks.
> ---
> hw/misc/mos6522.c | 67 ++++++++++++++++++++++++++++++++++++-----------
> 1 file changed, 52 insertions(+), 15 deletions(-)
>
> diff --git a/hw/misc/mos6522.c b/hw/misc/mos6522.c
> index 57f13db266..aa3bfe1afd 100644
> --- a/hw/misc/mos6522.c
> +++ b/hw/misc/mos6522.c
> @@ -38,8 +38,10 @@
>
> /* XXX: implement all timer modes */
>
> -static void mos6522_timer_update(MOS6522State *s, MOS6522Timer *ti,
> - int64_t current_time);
> +static void mos6522_timer1_update(MOS6522State *s, MOS6522Timer *ti,
> + int64_t current_time);
> +static void mos6522_timer2_update(MOS6522State *s, MOS6522Timer *ti,
> + int64_t current_time);
>
> static void mos6522_update_irq(MOS6522State *s)
> {
> @@ -98,7 +100,11 @@ static void set_counter(MOS6522State *s, MOS6522Timer
> *ti, unsigned int val)
> trace_mos6522_set_counter(1 + ti->index, val);
> ti->load_time = get_load_time(s, ti);
> ti->counter_value = val;
> - mos6522_timer_update(s, ti, ti->load_time);
> + if (ti->index == 0) {
> + mos6522_timer1_update(s, ti, ti->load_time);
> + } else {
> + mos6522_timer2_update(s, ti, ti->load_time);
> + }
> }
>
> static int64_t get_next_irq_time(MOS6522State *s, MOS6522Timer *ti,
> @@ -130,19 +136,34 @@ static int64_t get_next_irq_time(MOS6522State *s,
> MOS6522Timer *ti,
> trace_mos6522_get_next_irq_time(ti->latch, d, next_time - d);
> next_time = muldiv64(next_time, NANOSECONDS_PER_SECOND, ti->frequency) +
> ti->load_time;
> +
> if (next_time <= current_time) {
> next_time = current_time + 1;
> }
> return next_time;
> }
>
> -static void mos6522_timer_update(MOS6522State *s, MOS6522Timer *ti,
> +static void mos6522_timer1_update(MOS6522State *s, MOS6522Timer *ti,
> + int64_t current_time)
> +{
> + if (!ti->timer) {
> + return;
> + }
> + if ((s->ier & T1_INT) == 0 || (s->acr & T1MODE) != T1MODE_CONT) {
> + timer_del(ti->timer);
> + } else {
> + ti->next_irq_time = get_next_irq_time(s, ti, current_time);
> + timer_mod(ti->timer, ti->next_irq_time);
> + }
> +}
> +
> +static void mos6522_timer2_update(MOS6522State *s, MOS6522Timer *ti,
> int64_t current_time)
> {
> if (!ti->timer) {
> return;
> }
> - if (ti->index == 0 && (s->acr & T1MODE) != T1MODE_CONT) {
> + if ((s->ier & T2_INT) == 0) {
> timer_del(ti->timer);
> } else {
> ti->next_irq_time = get_next_irq_time(s, ti, current_time);
> @@ -155,7 +176,7 @@ static void mos6522_timer1(void *opaque)
> MOS6522State *s = opaque;
> MOS6522Timer *ti = &s->timers[0];
>
> - mos6522_timer_update(s, ti, ti->next_irq_time);
> + mos6522_timer1_update(s, ti, ti->next_irq_time);
> s->ifr |= T1_INT;
> mos6522_update_irq(s);
> }
> @@ -165,7 +186,7 @@ static void mos6522_timer2(void *opaque)
> MOS6522State *s = opaque;
> MOS6522Timer *ti = &s->timers[1];
>
> - mos6522_timer_update(s, ti, ti->next_irq_time);
> + mos6522_timer2_update(s, ti, ti->next_irq_time);
> s->ifr |= T2_INT;
> mos6522_update_irq(s);
> }
> @@ -204,7 +225,16 @@ uint64_t mos6522_read(void *opaque, hwaddr addr,
> unsigned size)
> {
> MOS6522State *s = opaque;
> uint32_t val;
> + int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
>
> + if (now >= s->timers[0].next_irq_time) {
> + mos6522_timer1_update(s, &s->timers[0], now);
> + s->ifr |= T1_INT;
> + }
> + if (now >= s->timers[1].next_irq_time) {
> + mos6522_timer2_update(s, &s->timers[1], now);
> + s->ifr |= T2_INT;
> + }
> switch (addr) {
> case VIA_REG_B:
> val = s->b;
> @@ -299,8 +329,8 @@ void mos6522_write(void *opaque, hwaddr addr, uint64_t
> val, unsigned size)
> break;
> case VIA_REG_T1CL:
> s->timers[0].latch = (s->timers[0].latch & 0xff00) | val;
> - mos6522_timer_update(s, &s->timers[0],
> - qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
> + mos6522_timer1_update(s, &s->timers[0],
> + qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
> break;
> case VIA_REG_T1CH:
> s->timers[0].latch = (s->timers[0].latch & 0xff) | (val << 8);
> @@ -309,14 +339,14 @@ void mos6522_write(void *opaque, hwaddr addr, uint64_t
> val, unsigned size)
> break;
> case VIA_REG_T1LL:
> s->timers[0].latch = (s->timers[0].latch & 0xff00) | val;
> - mos6522_timer_update(s, &s->timers[0],
> - qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
> + mos6522_timer1_update(s, &s->timers[0],
> + qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
> break;
> case VIA_REG_T1LH:
> s->timers[0].latch = (s->timers[0].latch & 0xff) | (val << 8);
> s->ifr &= ~T1_INT;
> - mos6522_timer_update(s, &s->timers[0],
> - qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
> + mos6522_timer1_update(s, &s->timers[0],
> + qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
> break;
> case VIA_REG_T2CL:
> s->timers[1].latch = (s->timers[1].latch & 0xff00) | val;
> @@ -334,8 +364,8 @@ void mos6522_write(void *opaque, hwaddr addr, uint64_t
> val, unsigned size)
> break;
> case VIA_REG_ACR:
> s->acr = val;
> - mos6522_timer_update(s, &s->timers[0],
> - qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
> + mos6522_timer1_update(s, &s->timers[0],
> + qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
> break;
> case VIA_REG_PCR:
> s->pcr = val;
> @@ -354,6 +384,11 @@ void mos6522_write(void *opaque, hwaddr addr, uint64_t
> val, unsigned size)
> s->ier &= ~val;
> }
> mos6522_update_irq(s);
> + /* if IER is modified starts needed timers */
> + mos6522_timer1_update(s, &s->timers[0],
> + qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
> + mos6522_timer2_update(s, &s->timers[1],
> + qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
> break;
> default:
> case VIA_REG_ANH:
> @@ -426,9 +461,11 @@ static void mos6522_reset(DeviceState *dev)
> s->timers[0].frequency = s->frequency;
> s->timers[0].latch = 0xffff;
> set_counter(s, &s->timers[0], 0xffff);
> + timer_del(s->timers[0].timer);
>
> s->timers[1].frequency = s->frequency;
> s->timers[1].latch = 0xffff;
> + timer_del(s->timers[1].timer);
> }
>
> static void mos6522_init(Object *obj)
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
signature.asc
Description: PGP signature
