diff options
| -rw-r--r-- | cpus.c | 8 | ||||
| -rw-r--r-- | qemu-common.h | 1 | ||||
| -rw-r--r-- | qemu-timer.c | 94 | ||||
| -rw-r--r-- | qemu-timer.h | 1 |
4 files changed, 102 insertions, 2 deletions
diff --git a/cpus.c b/cpus.c index cbeac7a40e..6a50199039 100644 --- a/cpus.c +++ b/cpus.c @@ -155,7 +155,7 @@ static bool cpu_thread_is_idle(CPUState *env) return true; } -static bool all_cpu_threads_idle(void) +bool all_cpu_threads_idle(void) { CPUState *env; @@ -739,6 +739,9 @@ static void qemu_tcg_wait_io_event(void) CPUState *env; while (all_cpu_threads_idle()) { + /* Start accounting real time to the virtual clock if the CPUs + are idle. */ + qemu_clock_warp(vm_clock); qemu_cond_wait(tcg_halt_cond, &qemu_global_mutex); } @@ -1073,6 +1076,9 @@ bool cpu_exec_all(void) { int r; + /* Account partial waits to the vm_clock. */ + qemu_clock_warp(vm_clock); + if (next_cpu == NULL) { next_cpu = first_cpu; } diff --git a/qemu-common.h b/qemu-common.h index 82e27c18d3..4f6037bab9 100644 --- a/qemu-common.h +++ b/qemu-common.h @@ -298,6 +298,7 @@ void qemu_notify_event(void); void qemu_cpu_kick(void *env); void qemu_cpu_kick_self(void); int qemu_cpu_is_self(void *env); +bool all_cpu_threads_idle(void); /* work queue */ struct qemu_work_item { diff --git a/qemu-timer.c b/qemu-timer.c index 50f1943afd..4959688895 100644 --- a/qemu-timer.c +++ b/qemu-timer.c @@ -153,6 +153,8 @@ void cpu_disable_ticks(void) struct QEMUClock { int type; int enabled; + + QEMUTimer *warp_timer; }; struct QEMUTimer { @@ -386,6 +388,90 @@ void qemu_clock_enable(QEMUClock *clock, int enabled) clock->enabled = enabled; } +static int64_t vm_clock_warp_start; + +static void icount_warp_rt(void *opaque) +{ + if (vm_clock_warp_start == -1) { + return; + } + + if (vm_running) { + int64_t clock = qemu_get_clock_ns(rt_clock); + int64_t warp_delta = clock - vm_clock_warp_start; + if (use_icount == 1) { + qemu_icount_bias += warp_delta; + } else { + /* + * In adaptive mode, do not let the vm_clock run too + * far ahead of real time. + */ + int64_t cur_time = cpu_get_clock(); + int64_t cur_icount = qemu_get_clock_ns(vm_clock); + int64_t delta = cur_time - cur_icount; + qemu_icount_bias += MIN(warp_delta, delta); + } + if (qemu_timer_expired(active_timers[QEMU_CLOCK_VIRTUAL], + qemu_get_clock_ns(vm_clock))) { + qemu_notify_event(); + } + } + vm_clock_warp_start = -1; +} + +void qemu_clock_warp(QEMUClock *clock) +{ + int64_t deadline; + + if (!clock->warp_timer) { + return; + } + + /* + * There are too many global variables to make the "warp" behavior + * applicable to other clocks. But a clock argument removes the + * need for if statements all over the place. + */ + assert(clock == vm_clock); + + /* + * If the CPUs have been sleeping, advance the vm_clock timer now. This + * ensures that the deadline for the timer is computed correctly below. + * This also makes sure that the insn counter is synchronized before the + * CPU starts running, in case the CPU is woken by an event other than + * the earliest vm_clock timer. + */ + icount_warp_rt(NULL); + if (!all_cpu_threads_idle() || !active_timers[clock->type]) { + qemu_del_timer(clock->warp_timer); + return; + } + + vm_clock_warp_start = qemu_get_clock_ns(rt_clock); + deadline = qemu_next_deadline(); + if (deadline > 0) { + /* + * Ensure the vm_clock proceeds even when the virtual CPU goes to + * sleep. Otherwise, the CPU might be waiting for a future timer + * interrupt to wake it up, but the interrupt never comes because + * the vCPU isn't running any insns and thus doesn't advance the + * vm_clock. + * + * An extreme solution for this problem would be to never let VCPUs + * sleep in icount mode if there is a pending vm_clock timer; rather + * time could just advance to the next vm_clock event. Instead, we + * do stop VCPUs and only advance vm_clock after some "real" time, + * (related to the time left until the next event) has passed. This + * rt_clock timer will do this. This avoids that the warps are too + * visible externally---for example, you will not be sending network + * packets continously instead of every 100ms. + */ + qemu_mod_timer(clock->warp_timer, vm_clock_warp_start + deadline); + } else { + qemu_notify_event(); + } +} + QEMUTimer *qemu_new_timer(QEMUClock *clock, int scale, QEMUTimerCB *cb, void *opaque) { @@ -454,8 +540,10 @@ static void qemu_mod_timer_ns(QEMUTimer *ts, int64_t expire_time) qemu_rearm_alarm_timer(alarm_timer); } /* Interrupt execution to force deadline recalculation. */ - if (use_icount) + qemu_clock_warp(ts->clock); + if (use_icount) { qemu_notify_event(); + } } } @@ -576,6 +664,10 @@ void configure_icount(const char *option) if (!option) return; +#ifdef CONFIG_IOTHREAD + vm_clock->warp_timer = qemu_new_timer_ns(rt_clock, icount_warp_rt, NULL); +#endif + if (strcmp(option, "auto") != 0) { icount_time_shift = strtol(option, NULL, 0); use_icount = 1; diff --git a/qemu-timer.h b/qemu-timer.h index 75d567578b..c01bcaba66 100644 --- a/qemu-timer.h +++ b/qemu-timer.h @@ -39,6 +39,7 @@ extern QEMUClock *host_clock; int64_t qemu_get_clock_ns(QEMUClock *clock); void qemu_clock_enable(QEMUClock *clock, int enabled); +void qemu_clock_warp(QEMUClock *clock); QEMUTimer *qemu_new_timer(QEMUClock *clock, int scale, QEMUTimerCB *cb, void *opaque); |