path: root/qemu-timer.c
diff options
authorJan Kiszka <jan.kiszka@siemens.com>2011-06-17 11:25:49 +0200
committerAnthony Liguori <aliguori@us.ibm.com>2011-07-23 11:26:12 -0500
commitd25f89c9e91d6c46b85969922411a211a6347a7d (patch)
tree6ef37246ff23527e8bc62fcf4f271bded16619d3 /qemu-timer.c
parent17604dac28b2410c021a4a52dcfa58e8803dfb24 (diff)
Register Linux dyntick timer as per-thread signal
Derived from kvm-tool patch http://thread.gmane.org/gmane.comp.emulators.kvm.devel/74309 Ingo Molnar pointed out that sending the timer signal to the whole process, just blocking it everywhere, is suboptimal with an increasing number of threads. QEMU is also using this pattern so far. Linux provides a (non-portable) way to restrict the signal to a single thread: We can use SIGEV_THREAD_ID unless we are forced to emulate signalfd via an additional thread. That case could theoretically be optimized as well, but it doesn't look worth bothering. Reviewed-by: Richard Henderson <rth@twiddle.net> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Diffstat (limited to 'qemu-timer.c')
1 files changed, 8 insertions, 0 deletions
diff --git a/qemu-timer.c b/qemu-timer.c
index f95374c7c1..30e8f1272e 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -831,6 +831,8 @@ static int64_t qemu_next_alarm_deadline(void)
#if defined(__linux__)
+#include "compatfd.h"
static int dynticks_start_timer(struct qemu_alarm_timer *t)
struct sigevent ev;
@@ -850,6 +852,12 @@ static int dynticks_start_timer(struct qemu_alarm_timer *t)
memset(&ev, 0, sizeof(ev));
ev.sigev_value.sival_int = 0;
ev.sigev_notify = SIGEV_SIGNAL;
+ if (qemu_signalfd_available()) {
+ ev.sigev_notify = SIGEV_THREAD_ID;
+ ev._sigev_un._tid = qemu_get_thread_id();
+ }
+#endif /* SIGEV_THREAD_ID */
ev.sigev_signo = SIGALRM;
if (timer_create(CLOCK_REALTIME, &ev, &host_timer)) {