diff options
Diffstat (limited to 'cpus.c')
| -rw-r--r-- | cpus.c | 70 |
1 files changed, 44 insertions, 26 deletions
@@ -105,6 +105,7 @@ static bool all_cpu_threads_idle(void) /* Protected by TimersState seqlock */ +static bool icount_sleep = true; static int64_t vm_clock_warp_start = -1; /* Conversion factor from emulated instructions to virtual clock ticks. */ static int icount_time_shift; @@ -393,15 +394,18 @@ void qemu_clock_warp(QEMUClockType type) return; } - /* - * If the CPUs have been sleeping, advance QEMU_CLOCK_VIRTUAL 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 QEMU_CLOCK_VIRTUAL timer. - */ - icount_warp_rt(NULL); - timer_del(icount_warp_timer); + if (icount_sleep) { + /* + * If the CPUs have been sleeping, advance QEMU_CLOCK_VIRTUAL 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 QEMU_CLOCK_VIRTUAL timer. + */ + icount_warp_rt(NULL); + timer_del(icount_warp_timer); + } if (!all_cpu_threads_idle()) { return; } @@ -425,23 +429,35 @@ void qemu_clock_warp(QEMUClockType type) * interrupt to wake it up, but the interrupt never comes because * the vCPU isn't running any insns and thus doesn't advance the * QEMU_CLOCK_VIRTUAL. - * - * An extreme solution for this problem would be to never let VCPUs - * sleep in icount mode if there is a pending QEMU_CLOCK_VIRTUAL - * timer; rather time could just advance to the next QEMU_CLOCK_VIRTUAL - * event. Instead, we do stop VCPUs and only advance QEMU_CLOCK_VIRTUAL - * after some "real" time, (related to the time left until the next - * event) has passed. The QEMU_CLOCK_VIRTUAL_RT clock will do this. - * This avoids that the warps are visible externally; for example, - * you will not be sending network packets continuously instead of - * every 100ms. */ - seqlock_write_lock(&timers_state.vm_clock_seqlock); - if (vm_clock_warp_start == -1 || vm_clock_warp_start > clock) { - vm_clock_warp_start = clock; + if (!icount_sleep) { + /* + * We never let VCPUs sleep in no sleep icount mode. + * If there is a pending QEMU_CLOCK_VIRTUAL timer we just advance + * to the next QEMU_CLOCK_VIRTUAL event and notify it. + * It is useful when we want a deterministic execution time, + * isolated from host latencies. + */ + seqlock_write_lock(&timers_state.vm_clock_seqlock); + timers_state.qemu_icount_bias += deadline; + seqlock_write_unlock(&timers_state.vm_clock_seqlock); + qemu_clock_notify(QEMU_CLOCK_VIRTUAL); + } else { + /* + * We do stop VCPUs and only advance QEMU_CLOCK_VIRTUAL after some + * "real" time, (related to the time left until the next event) has + * passed. The QEMU_CLOCK_VIRTUAL_RT clock will do this. + * This avoids that the warps are visible externally; for example, + * you will not be sending network packets continuously instead of + * every 100ms. + */ + seqlock_write_lock(&timers_state.vm_clock_seqlock); + if (vm_clock_warp_start == -1 || vm_clock_warp_start > clock) { + vm_clock_warp_start = clock; + } + seqlock_write_unlock(&timers_state.vm_clock_seqlock); + timer_mod_anticipate(icount_warp_timer, clock + deadline); } - seqlock_write_unlock(&timers_state.vm_clock_seqlock); - timer_mod_anticipate(icount_warp_timer, clock + deadline); } else if (deadline == 0) { qemu_clock_notify(QEMU_CLOCK_VIRTUAL); } @@ -504,9 +520,11 @@ void configure_icount(QemuOpts *opts, Error **errp) } return; } + if (icount_sleep) { + icount_warp_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL_RT, + icount_warp_rt, NULL); + } icount_align_option = qemu_opt_get_bool(opts, "align", false); - icount_warp_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL_RT, - icount_warp_rt, NULL); if (strcmp(option, "auto") != 0) { errno = 0; icount_time_shift = strtol(option, &rem_str, 0); |