As windows guest use rtc as the clock source device, and access rtc frequently. Let's move the rtc memory region outside BQL to decrease overhead for windows guests. Meanwhile, adding a new lock to avoid different vCPUs access the RTC together.
I tested PCMark 8 (https://www.futuremark.com/benchmarks/pcmark) in win7 guest and got the below results: Guest: 2U2G Before applying the patch: Your Work 2.0 score: 2000 Web Browsing - JunglePin 0.334s Web Browsing - Amazonia 0.132s Writing 3.59s Spreadsheet 70.13s Video Chat v2/Video Chat playback 1 v2 22.8 fps Video Chat v2/Video Chat encoding v2 307.0 ms Benchmark duration 1h 35min 46s After applying the patch: Your Work 2.0 score: 2040 Web Browsing - JunglePin 0.345s Web Browsing - Amazonia 0.132s Writing 3.56s Spreadsheet 67.83s Video Chat v2/Video Chat playback 1 v2 28.7 fps Video Chat v2/Video Chat encoding v2 324.7 ms Benchmark duration 1h 32min 5s Test results show that optimization is effective under stressful situations. Signed-off-by: Gonglei <arei.gong...@huawei.com> --- v3->v2: a) fix a typo, 's/rasie/raise/' [Peter] b) change commit message [Peter] v2->v1: a)Adding a new lock to avoid different vCPUs access the RTC together. [Paolo] b)Taking the BQL before raising the outbound IRQ line. [Peter] c)Don't hold BQL if it was holden. [Peter] hw/timer/mc146818rtc.c | 55 ++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 47 insertions(+), 8 deletions(-) diff --git a/hw/timer/mc146818rtc.c b/hw/timer/mc146818rtc.c index 35a05a6..f0a2a62 100644 --- a/hw/timer/mc146818rtc.c +++ b/hw/timer/mc146818rtc.c @@ -85,6 +85,7 @@ typedef struct RTCState { uint16_t irq_reinject_on_ack_count; uint32_t irq_coalesced; uint32_t period; + QemuMutex rtc_lock; QEMUTimer *coalesced_timer; Notifier clock_reset_notifier; LostTickPolicy lost_tick_policy; @@ -125,6 +126,36 @@ static void rtc_coalesced_timer_update(RTCState *s) } } +static void rtc_raise_irq(RTCState *s) +{ + bool unlocked = !qemu_mutex_iothread_locked(); + + if (unlocked) { + qemu_mutex_lock_iothread(); + } + + qemu_irq_raise(s->irq); + + if (unlocked) { + qemu_mutex_unlock_iothread(); + } +} + +static void rtc_lower_irq(RTCState *s) +{ + bool unlocked = !qemu_mutex_iothread_locked(); + + if (unlocked) { + qemu_mutex_lock_iothread(); + } + + qemu_irq_lower(s->irq); + + if (unlocked) { + qemu_mutex_unlock_iothread(); + } +} + static QLIST_HEAD(, RTCState) rtc_devices = QLIST_HEAD_INITIALIZER(rtc_devices); @@ -141,7 +172,7 @@ void qmp_rtc_reset_reinjection(Error **errp) static bool rtc_policy_slew_deliver_irq(RTCState *s) { apic_reset_irq_delivered(); - qemu_irq_raise(s->irq); + rtc_raise_irq(s); return apic_get_irq_delivered(); } @@ -277,8 +308,9 @@ static void rtc_periodic_timer(void *opaque) DPRINTF_C("cmos: coalesced irqs increased to %d\n", s->irq_coalesced); } - } else - qemu_irq_raise(s->irq); + } else { + rtc_raise_irq(s); + } } } @@ -459,7 +491,7 @@ static void rtc_update_timer(void *opaque) s->cmos_data[RTC_REG_C] |= irqs; if ((new_irqs & s->cmos_data[RTC_REG_B]) != 0) { s->cmos_data[RTC_REG_C] |= REG_C_IRQF; - qemu_irq_raise(s->irq); + rtc_raise_irq(s); } check_update_timer(s); } @@ -471,6 +503,7 @@ static void cmos_ioport_write(void *opaque, hwaddr addr, uint32_t old_period; bool update_periodic_timer; + qemu_mutex_lock(&s->rtc_lock); if ((addr & 1) == 0) { s->cmos_index = data & 0x7f; } else { @@ -560,10 +593,10 @@ static void cmos_ioport_write(void *opaque, hwaddr addr, * becomes enabled, raise an interrupt immediately. */ if (data & s->cmos_data[RTC_REG_C] & REG_C_MASK) { s->cmos_data[RTC_REG_C] |= REG_C_IRQF; - qemu_irq_raise(s->irq); + rtc_raise_irq(s); } else { s->cmos_data[RTC_REG_C] &= ~REG_C_IRQF; - qemu_irq_lower(s->irq); + rtc_lower_irq(s); } s->cmos_data[RTC_REG_B] = data; @@ -583,6 +616,7 @@ static void cmos_ioport_write(void *opaque, hwaddr addr, break; } } + qemu_mutex_unlock(&s->rtc_lock); } static inline int rtc_to_bcd(RTCState *s, int a) @@ -710,6 +744,7 @@ static uint64_t cmos_ioport_read(void *opaque, hwaddr addr, if ((addr & 1) == 0) { return 0xff; } else { + qemu_mutex_lock(&s->rtc_lock); switch(s->cmos_index) { case RTC_IBM_PS2_CENTURY_BYTE: s->cmos_index = RTC_CENTURY; @@ -737,7 +772,7 @@ static uint64_t cmos_ioport_read(void *opaque, hwaddr addr, break; case RTC_REG_C: ret = s->cmos_data[s->cmos_index]; - qemu_irq_lower(s->irq); + rtc_lower_irq(s); s->cmos_data[RTC_REG_C] = 0x00; if (ret & (REG_C_UF | REG_C_AF)) { check_update_timer(s); @@ -762,6 +797,7 @@ static uint64_t cmos_ioport_read(void *opaque, hwaddr addr, } CMOS_DPRINTF("cmos: read index=0x%02x val=0x%02x\n", s->cmos_index, ret); + qemu_mutex_unlock(&s->rtc_lock); return ret; } } @@ -909,7 +945,7 @@ static void rtc_reset(void *opaque) s->cmos_data[RTC_REG_C] &= ~(REG_C_UF | REG_C_IRQF | REG_C_PF | REG_C_AF); check_update_timer(s); - qemu_irq_lower(s->irq); + rtc_lower_irq(s); if (s->lost_tick_policy == LOST_TICK_POLICY_SLEW) { s->irq_coalesced = 0; @@ -960,6 +996,8 @@ static void rtc_realizefn(DeviceState *dev, Error **errp) rtc_set_date_from_host(isadev); + qemu_mutex_init(&s->rtc_lock); + switch (s->lost_tick_policy) { #ifdef TARGET_I386 case LOST_TICK_POLICY_SLEW: @@ -986,6 +1024,7 @@ static void rtc_realizefn(DeviceState *dev, Error **errp) qemu_register_suspend_notifier(&s->suspend_notifier); memory_region_init_io(&s->io, OBJECT(s), &cmos_ops, s, "rtc", 2); + memory_region_clear_global_locking(&s->io); isa_register_ioport(isadev, &s->io, base); qdev_set_legacy_instance_id(dev, base, 3); -- 1.8.3.1
