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authorPaolo Bonzini <pbonzini@redhat.com>2011-06-09 13:10:25 +0200
committerAnthony Liguori <aliguori@us.ibm.com>2011-07-23 11:18:57 -0500
commit84682834eb8f654da5e03a92930d80b8ae0d3065 (patch)
tree3aeeec0738326f2e5e424820cbb3bab21fa855d6 /qemu-timer.c
parent46daff13c854769bfa8c51e77719325ea0f47b1b (diff)
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qemu-timer: change unix timer to dynticks
A timer that wakes up every millisecond puts a lot of stress on the iothread. The large amount of IPIs causes very high context switch activity, making emulation slow and the UI unusable. This is by the way the same reason why the Windows timers were switched to dynticks. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Tested-by: Alexander Graf <agraf@suse.de> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Diffstat (limited to 'qemu-timer.c')
-rw-r--r--qemu-timer.c40
1 files changed, 28 insertions, 12 deletions
diff --git a/qemu-timer.c b/qemu-timer.c
index 72066c7..67c2974 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -218,6 +218,7 @@ static void win32_rearm_timer(struct qemu_alarm_timer *t);
static int unix_start_timer(struct qemu_alarm_timer *t);
static void unix_stop_timer(struct qemu_alarm_timer *t);
+static void unix_rearm_timer(struct qemu_alarm_timer *t);
#ifdef __linux__
@@ -290,7 +291,7 @@ static struct qemu_alarm_timer alarm_timers[] = {
{"dynticks", dynticks_start_timer,
dynticks_stop_timer, dynticks_rearm_timer},
#endif
- {"unix", unix_start_timer, unix_stop_timer, NULL},
+ {"unix", unix_start_timer, unix_stop_timer, unix_rearm_timer},
#else
{"mmtimer", mm_start_timer, mm_stop_timer, NULL},
{"mmtimer2", mm_start_timer, mm_stop_timer, mm_rearm_timer},
@@ -890,8 +891,6 @@ static void dynticks_rearm_timer(struct qemu_alarm_timer *t)
static int unix_start_timer(struct qemu_alarm_timer *t)
{
struct sigaction act;
- struct itimerval itv;
- int err;
/* timer signal */
sigfillset(&act.sa_mask);
@@ -899,18 +898,35 @@ static int unix_start_timer(struct qemu_alarm_timer *t)
act.sa_handler = host_alarm_handler;
sigaction(SIGALRM, &act, NULL);
+ return 0;
+}
- itv.it_interval.tv_sec = 0;
- /* for i386 kernel 2.6 to get 1 ms */
- itv.it_interval.tv_usec = 999;
- itv.it_value.tv_sec = 0;
- itv.it_value.tv_usec = 10 * 1000;
+static void unix_rearm_timer(struct qemu_alarm_timer *t)
+{
+ struct itimerval itv;
+ int64_t nearest_delta_ns = INT64_MAX;
+ int err;
- err = setitimer(ITIMER_REAL, &itv, NULL);
- if (err)
- return -1;
+ assert(alarm_has_dynticks(t));
+ if (!active_timers[QEMU_CLOCK_REALTIME] &&
+ !active_timers[QEMU_CLOCK_VIRTUAL] &&
+ !active_timers[QEMU_CLOCK_HOST])
+ return;
- return 0;
+ nearest_delta_ns = qemu_next_alarm_deadline();
+ if (nearest_delta_ns < MIN_TIMER_REARM_NS)
+ nearest_delta_ns = MIN_TIMER_REARM_NS;
+
+ itv.it_interval.tv_sec = 0;
+ itv.it_interval.tv_usec = 0; /* 0 for one-shot timer */
+ itv.it_value.tv_sec = nearest_delta_ns / 1000000000;
+ itv.it_value.tv_usec = (nearest_delta_ns % 1000000000) / 1000;
+ err = setitimer(ITIMER_REAL, &itv, NULL);
+ if (err) {
+ perror("setitimer");
+ fprintf(stderr, "Internal timer error: aborting\n");
+ exit(1);
+ }
}
static void unix_stop_timer(struct qemu_alarm_timer *t)