| Message ID | 1517493091-23620-1-git-send-email-arei.gonglei@huawei.com |
|---|---|
| State | New |
| Headers | show |
| Series | rtc: placing RTC memory region outside BQL | expand |
diff --git a/hw/timer/mc146818rtc.c b/hw/timer/mc146818rtc.c index 35a05a6..d9d99c5 100644 --- a/hw/timer/mc146818rtc.c +++ b/hw/timer/mc146818rtc.c @@ -986,6 +986,7 @@ static void rtc_realizefn(DeviceState *dev, Error **errp) qemu_register_suspend_notifier(&s->suspend_notifier); memory_region_init_io(&s->io, OBJECT(s), &cmos_ops, s, "rtc", 2); + memory_region_clear_global_locking(&s->io); isa_register_ioport(isadev, &s->io, base); qdev_set_legacy_instance_id(dev, base, 3);
As windows guest use rtc as the clock source device, and access rtc frequently. Let's move the rtc memory region outside BQL to decrease overhead for windows guests. $ cat strace_c.sh strace -tt -p $1 -c -o result_$1.log & sleep $2 pid=$(pidof strace) kill $pid cat result_$1.log Before appling this change: $ ./strace_c.sh 10528 30 % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 93.87 0.119070 30 4000 ppoll 3.27 0.004148 2 2038 ioctl 2.66 0.003370 2 2014 futex 0.09 0.000113 1 106 read 0.09 0.000109 1 104 io_getevents 0.02 0.000029 1 30 poll 0.00 0.000000 0 1 write ------ ----------- ----------- --------- --------- ---------------- 100.00 0.126839 8293 total After appling the change: $ ./strace_c.sh 23829 30 % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 92.86 0.067441 16 4094 ppoll 4.85 0.003522 2 2136 ioctl 1.17 0.000850 4 189 futex 0.54 0.000395 2 202 read 0.52 0.000379 2 202 io_getevents 0.05 0.000037 1 30 poll ------ ----------- ----------- --------- --------- ---------------- 100.00 0.072624 6853 total The futex call number decreases ~90.6% on an idle windows 7 guest. Signed-off-by: Gonglei <arei.gonglei@huawei.com> --- hw/timer/mc146818rtc.c | 1 + 1 file changed, 1 insertion(+)