[PULL 5/9] qemu-timer: Skip empty timer lists before locking in qemu_clock_deadline_ns_all

[Richard Henderson]

From: Idan Horowitz <idan.horowitz@gmail.com>

This decreases qemu_clock_deadline_ns_all's share from 23.2% to 13% in a
profile of icount-enabled aarch64-softmmu.

Signed-off-by: Idan Horowitz <idan.horowitz@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220114004358.299534-2-idan.horowitz@gmail.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 util/qemu-timer.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/util/qemu-timer.c b/util/qemu-timer.c
index a670a57881..6a0de33dd2 100644
--- a/util/qemu-timer.c
+++ b/util/qemu-timer.c
@@ -261,6 +261,9 @@ int64_t qemu_clock_deadline_ns_all(QEMUClockType type, int 
attr_mask)
     }
 
     QLIST_FOREACH(timer_list, &clock->timerlists, list) {
+        if (!qatomic_read(&timer_list->active_timers)) {
+            continue;
+        }
         qemu_mutex_lock(&timer_list->active_timers_lock);
         ts = timer_list->active_timers;
         /* Skip all external timers */
-- 
2.34.1