Add instruction counter.
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@4799 c046a42c-6fe2-441c-8c8c-71466251a162
diff --git a/vl.c b/vl.c
index 908aa39..72ce67b 100644
--- a/vl.c
+++ b/vl.c
@@ -239,6 +239,14 @@
static CPUState *cur_cpu;
static CPUState *next_cpu;
static int event_pending = 1;
+/* Conversion factor from emulated instrctions to virtual clock ticks. */
+static int icount_time_shift;
+/* Arbitrarily pick 1MIPS as the minimum alowable speed. */
+#define MAX_ICOUNT_SHIFT 10
+/* Compensate for varying guest execution speed. */
+static int64_t qemu_icount_bias;
+QEMUTimer *icount_rt_timer;
+QEMUTimer *icount_vm_timer;
#define TFR(expr) do { if ((expr) != -1) break; } while (errno == EINTR)
@@ -733,9 +741,22 @@
return tv.tv_sec * 1000000000LL + (tv.tv_usec * 1000);
}
}
-
#endif
+/* Return the virtual CPU time, based on the instruction counter. */
+static int64_t cpu_get_icount(void)
+{
+ int64_t icount;
+ CPUState *env = cpu_single_env;;
+ icount = qemu_icount;
+ if (env) {
+ if (!can_do_io(env))
+ fprintf(stderr, "Bad clock read\n");
+ icount -= (env->icount_decr.u16.low + env->icount_extra);
+ }
+ return qemu_icount_bias + (icount << icount_time_shift);
+}
+
/***********************************************************/
/* guest cycle counter */
@@ -747,6 +768,9 @@
/* return the host CPU cycle counter and handle stop/restart */
int64_t cpu_get_ticks(void)
{
+ if (use_icount) {
+ return cpu_get_icount();
+ }
if (!cpu_ticks_enabled) {
return cpu_ticks_offset;
} else {
@@ -878,6 +902,71 @@
#endif /* _WIN32 */
+/* Correlation between real and virtual time is always going to be
+ farly approximate, so ignore small variation.
+ When the guest is idle real and virtual time will be aligned in
+ the IO wait loop. */
+#define ICOUNT_WOBBLE (QEMU_TIMER_BASE / 10)
+
+static void icount_adjust(void)
+{
+ int64_t cur_time;
+ int64_t cur_icount;
+ int64_t delta;
+ static int64_t last_delta;
+ /* If the VM is not running, then do nothing. */
+ if (!vm_running)
+ return;
+
+ cur_time = cpu_get_clock();
+ cur_icount = qemu_get_clock(vm_clock);
+ delta = cur_icount - cur_time;
+ /* FIXME: This is a very crude algorithm, somewhat prone to oscillation. */
+ if (delta > 0
+ && last_delta + ICOUNT_WOBBLE < delta * 2
+ && icount_time_shift > 0) {
+ /* The guest is getting too far ahead. Slow time down. */
+ icount_time_shift--;
+ }
+ if (delta < 0
+ && last_delta - ICOUNT_WOBBLE > delta * 2
+ && icount_time_shift < MAX_ICOUNT_SHIFT) {
+ /* The guest is getting too far behind. Speed time up. */
+ icount_time_shift++;
+ }
+ last_delta = delta;
+ qemu_icount_bias = cur_icount - (qemu_icount << icount_time_shift);
+}
+
+static void icount_adjust_rt(void * opaque)
+{
+ qemu_mod_timer(icount_rt_timer,
+ qemu_get_clock(rt_clock) + 1000);
+ icount_adjust();
+}
+
+static void icount_adjust_vm(void * opaque)
+{
+ qemu_mod_timer(icount_vm_timer,
+ qemu_get_clock(vm_clock) + QEMU_TIMER_BASE / 10);
+ icount_adjust();
+}
+
+static void init_icount_adjust(void)
+{
+ /* Have both realtime and virtual time triggers for speed adjustment.
+ The realtime trigger catches emulated time passing too slowly,
+ the virtual time trigger catches emulated time passing too fast.
+ Realtime triggers occur even when idle, so use them less frequently
+ than VM triggers. */
+ icount_rt_timer = qemu_new_timer(rt_clock, icount_adjust_rt, NULL);
+ qemu_mod_timer(icount_rt_timer,
+ qemu_get_clock(rt_clock) + 1000);
+ icount_vm_timer = qemu_new_timer(vm_clock, icount_adjust_vm, NULL);
+ qemu_mod_timer(icount_vm_timer,
+ qemu_get_clock(vm_clock) + QEMU_TIMER_BASE / 10);
+}
+
static struct qemu_alarm_timer alarm_timers[] = {
#ifndef _WIN32
#ifdef __linux__
@@ -914,6 +1003,7 @@
int count = (sizeof(alarm_timers) / sizeof(*alarm_timers)) - 1;
char *arg;
char *name;
+ struct qemu_alarm_timer tmp;
if (!strcmp(opt, "?")) {
show_available_alarms();
@@ -925,8 +1015,6 @@
/* Reorder the array */
name = strtok(arg, ",");
while (name) {
- struct qemu_alarm_timer tmp;
-
for (i = 0; i < count && alarm_timers[i].name; i++) {
if (!strcmp(alarm_timers[i].name, name))
break;
@@ -954,7 +1042,7 @@
free(arg);
if (cur) {
- /* Disable remaining timers */
+ /* Disable remaining timers */
for (i = cur; i < count; i++)
alarm_timers[i].name = NULL;
} else {
@@ -1039,9 +1127,15 @@
*pt = ts;
/* Rearm if necessary */
- if ((alarm_timer->flags & ALARM_FLAG_EXPIRED) == 0 &&
- pt == &active_timers[ts->clock->type])
- qemu_rearm_alarm_timer(alarm_timer);
+ if (pt == &active_timers[ts->clock->type]) {
+ if ((alarm_timer->flags & ALARM_FLAG_EXPIRED) == 0) {
+ qemu_rearm_alarm_timer(alarm_timer);
+ }
+ /* Interrupt execution to force deadline recalculation. */
+ if (use_icount && cpu_single_env) {
+ cpu_interrupt(cpu_single_env, CPU_INTERRUPT_EXIT);
+ }
+ }
}
int qemu_timer_pending(QEMUTimer *ts)
@@ -1085,7 +1179,11 @@
return get_clock() / 1000000;
default:
case QEMU_TIMER_VIRTUAL:
- return cpu_get_clock();
+ if (use_icount) {
+ return cpu_get_icount();
+ } else {
+ return cpu_get_clock();
+ }
}
}
@@ -1184,8 +1282,9 @@
}
#endif
if (alarm_has_dynticks(alarm_timer) ||
- qemu_timer_expired(active_timers[QEMU_TIMER_VIRTUAL],
- qemu_get_clock(vm_clock)) ||
+ (!use_icount &&
+ qemu_timer_expired(active_timers[QEMU_TIMER_VIRTUAL],
+ qemu_get_clock(vm_clock))) ||
qemu_timer_expired(active_timers[QEMU_TIMER_REALTIME],
qemu_get_clock(rt_clock))) {
#ifdef _WIN32
@@ -1209,28 +1308,45 @@
}
}
-static uint64_t qemu_next_deadline(void)
+static int64_t qemu_next_deadline(void)
{
- int64_t nearest_delta_us = INT64_MAX;
- int64_t vmdelta_us;
-
- if (active_timers[QEMU_TIMER_REALTIME])
- nearest_delta_us = (active_timers[QEMU_TIMER_REALTIME]->expire_time -
- qemu_get_clock(rt_clock))*1000;
+ int64_t delta;
if (active_timers[QEMU_TIMER_VIRTUAL]) {
- /* round up */
- vmdelta_us = (active_timers[QEMU_TIMER_VIRTUAL]->expire_time -
- qemu_get_clock(vm_clock)+999)/1000;
- if (vmdelta_us < nearest_delta_us)
- nearest_delta_us = vmdelta_us;
+ delta = active_timers[QEMU_TIMER_VIRTUAL]->expire_time -
+ qemu_get_clock(vm_clock);
+ } else {
+ /* To avoid problems with overflow limit this to 2^32. */
+ delta = INT32_MAX;
}
- /* Avoid arming the timer to negative, zero, or too low values */
- if (nearest_delta_us <= MIN_TIMER_REARM_US)
- nearest_delta_us = MIN_TIMER_REARM_US;
+ if (delta < 0)
+ delta = 0;
- return nearest_delta_us;
+ return delta;
+}
+
+static uint64_t qemu_next_deadline_dyntick(void)
+{
+ int64_t delta;
+ int64_t rtdelta;
+
+ if (use_icount)
+ delta = INT32_MAX;
+ else
+ delta = (qemu_next_deadline() + 999) / 1000;
+
+ if (active_timers[QEMU_TIMER_REALTIME]) {
+ rtdelta = (active_timers[QEMU_TIMER_REALTIME]->expire_time -
+ qemu_get_clock(rt_clock))*1000;
+ if (rtdelta < delta)
+ delta = rtdelta;
+ }
+
+ if (delta < MIN_TIMER_REARM_US)
+ delta = MIN_TIMER_REARM_US;
+
+ return delta;
}
#ifndef _WIN32
@@ -1386,7 +1502,7 @@
!active_timers[QEMU_TIMER_VIRTUAL])
return;
- nearest_delta_us = qemu_next_deadline();
+ nearest_delta_us = qemu_next_deadline_dyntick();
/* check whether a timer is already running */
if (timer_gettime(host_timer, &timeout)) {
@@ -1513,7 +1629,7 @@
!active_timers[QEMU_TIMER_VIRTUAL])
return;
- nearest_delta_us = qemu_next_deadline();
+ nearest_delta_us = qemu_next_deadline_dyntick();
nearest_delta_us /= 1000;
timeKillEvent(data->timerId);
@@ -7068,10 +7184,33 @@
#ifdef CONFIG_PROFILER
ti = profile_getclock();
#endif
+ if (use_icount) {
+ int64_t count;
+ int decr;
+ qemu_icount -= (env->icount_decr.u16.low + env->icount_extra);
+ env->icount_decr.u16.low = 0;
+ env->icount_extra = 0;
+ count = qemu_next_deadline();
+ count = (count + (1 << icount_time_shift) - 1)
+ >> icount_time_shift;
+ qemu_icount += count;
+ decr = (count > 0xffff) ? 0xffff : count;
+ count -= decr;
+ env->icount_decr.u16.low = decr;
+ env->icount_extra = count;
+ }
ret = cpu_exec(env);
#ifdef CONFIG_PROFILER
qemu_time += profile_getclock() - ti;
#endif
+ if (use_icount) {
+ /* Fold pending instructions back into the
+ instruction counter, and clear the interrupt flag. */
+ qemu_icount -= (env->icount_decr.u16.low
+ + env->icount_extra);
+ env->icount_decr.u32 = 0;
+ env->icount_extra = 0;
+ }
next_cpu = env->next_cpu ?: first_cpu;
if (event_pending && likely(ret != EXCP_DEBUG)) {
ret = EXCP_INTERRUPT;
@@ -7115,10 +7254,46 @@
}
/* If all cpus are halted then wait until the next IRQ */
/* XXX: use timeout computed from timers */
- if (ret == EXCP_HALTED)
- timeout = 10;
- else
+ if (ret == EXCP_HALTED) {
+ if (use_icount) {
+ int64_t add;
+ int64_t delta;
+ /* Advance virtual time to the next event. */
+ if (use_icount == 1) {
+ /* When not using an adaptive execution frequency
+ we tend to get badly out of sync with real time,
+ so just delay for a resonable amount of time. */
+ delta = 0;
+ } else {
+ delta = cpu_get_icount() - cpu_get_clock();
+ }
+ if (delta > 0) {
+ /* If virtual time is ahead of real time then just
+ wait for IO. */
+ timeout = (delta / 1000000) + 1;
+ } else {
+ /* Wait for either IO to occur or the next
+ timer event. */
+ add = qemu_next_deadline();
+ /* We advance the timer before checking for IO.
+ Limit the amount we advance so that early IO
+ activity won't get the guest too far ahead. */
+ if (add > 10000000)
+ add = 10000000;
+ delta += add;
+ add = (add + (1 << icount_time_shift) - 1)
+ >> icount_time_shift;
+ qemu_icount += add;
+ timeout = delta / 1000000;
+ if (timeout < 0)
+ timeout = 0;
+ }
+ } else {
+ timeout = 10;
+ }
+ } else {
timeout = 0;
+ }
} else {
timeout = 10;
}
@@ -7270,6 +7445,8 @@
"-clock force the use of the given methods for timer alarm.\n"
" To see what timers are available use -clock ?\n"
"-startdate select initial date of the clock\n"
+ "-icount [N|auto]\n"
+ " Enable virtual instruction counter with 2^N clock ticks per instructon\n"
"\n"
"During emulation, the following keys are useful:\n"
"ctrl-alt-f toggle full screen\n"
@@ -7374,6 +7551,7 @@
QEMU_OPTION_clock,
QEMU_OPTION_startdate,
QEMU_OPTION_tb_size,
+ QEMU_OPTION_icount,
};
typedef struct QEMUOption {
@@ -7486,6 +7664,7 @@
{ "clock", HAS_ARG, QEMU_OPTION_clock },
{ "startdate", HAS_ARG, QEMU_OPTION_startdate },
{ "tb-size", HAS_ARG, QEMU_OPTION_tb_size },
+ { "icount", HAS_ARG, QEMU_OPTION_icount },
{ NULL },
};
@@ -8310,6 +8489,14 @@
if (tb_size < 0)
tb_size = 0;
break;
+ case QEMU_OPTION_icount:
+ use_icount = 1;
+ if (strcmp(optarg, "auto") == 0) {
+ icount_time_shift = -1;
+ } else {
+ icount_time_shift = strtol(optarg, NULL, 0);
+ }
+ break;
}
}
}
@@ -8395,6 +8582,13 @@
init_timers();
init_timer_alarm();
qemu_aio_init();
+ if (use_icount && icount_time_shift < 0) {
+ use_icount = 2;
+ /* 125MIPS seems a reasonable initial guess at the guest speed.
+ It will be corrected fairly quickly anyway. */
+ icount_time_shift = 3;
+ init_icount_adjust();
+ }
#ifdef _WIN32
socket_init();
