On 26/05/2017 05:21, Xiao Guangrong wrote:
> On 05/26/2017 12:03 AM, Paolo Bonzini wrote:
>> On 25/05/2017 05:19, guangrong.xiao@xxxxxxxxx wrote:
>> I'm not sure I understand. Why would clock_step(1000) not be a good
>> replacement for nsleep(1000)?
>
> We can not. As we use the real time to compare with the time that is
> passed in the VM, however, clock_step() is not a real time based clock
> source which immediately injects a time step to the VM regardless how
> much real time elapsed.
The trick lies in not using the real time for comparison, but the number
of time steps that were injected (or directly nanoseconds), like this:
--- a/tests/rtc-periodic-test.c
+++ b/tests/rtc-periodic-test.c
@@ -21,29 +21,29 @@
#include "rtc-test.h"
-#define RTC_PERIOD_CODE1 13
-#define RTC_PERIOD_CODE2 15
+#define RTC_PERIOD_CODE1 13 /* 8 Hz */
+#define RTC_PERIOD_CODE2 15 /* 2 Hz */
#define RTC_PERIOD_TEST_NR 50
-static void nsleep(int64_t nsecs)
-{
- const struct timespec val = { .tv_nsec = nsecs };
- nanosleep(&val, NULL);
-}
-
-static void wait_periodic_interrupt(void)
+static uint64_t wait_periodic_interrupt(void)
{
- while (1) {
- if (get_irq(RTC_ISA_IRQ)) {
- break;
- }
-
- /* 1 us.*/
- nsleep(1000);
+ uint64_t real_time = 0;
+ while (!get_irq(RTC_ISA_IRQ)) {
+ /*
+ * about 2 ms. It's more than enough given the period
+ * that we set above.
+ */
+ clock_step(NANOSECONDS_PER_SECOND / 512);
+ real_time += NANOSECONDS_PER_SECOND / 512;
}
g_assert((cmos_read(RTC_REG_C) & REG_C_PF) != 0);
+ return real_time;
}
static void periodic_timer(void)
@@ -58,17 +58,15 @@
/* enable periodic interrupt after properly configure the period. */
cmos_write(RTC_REG_B, cmos_read(RTC_REG_B) | REG_B_PIE);
- real_time = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+ real_time = 0;
for (i = 0; i < RTC_PERIOD_TEST_NR; i++) {
cmos_write(RTC_REG_A, RTC_PERIOD_CODE1);
- wait_periodic_interrupt();
+ real_time += wait_periodic_interrupt();
cmos_write(RTC_REG_A, RTC_PERIOD_CODE2);
- wait_periodic_interrupt();
+ real_time += wait_periodic_interrupt();
}
- real_time = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - real_time;
-
period_clocks = periodic_period_to_clock(RTC_PERIOD_CODE1) +
periodic_period_to_clock(RTC_PERIOD_CODE2);
period_clocks *= RTC_PERIOD_TEST_NR;
@@ -85,7 +83,7 @@
g_test_init(&argc, &argv, NULL);
- s = qtest_start("-rtc clock=host");
+ s = qtest_start("-rtc clock=vm");
qtest_irq_intercept_in(s, "ioapic");
qtest_add_func("/rtc/periodic/interrupt", periodic_timer);
Even better, the vm_clock time can be returned directly from
clock_step(), and you can even speed up the test by using
clock_step_next():
--- a/tests/rtc-periodic-test.c
+++ b/tests/rtc-periodic-test.c
@@ -21,29 +21,19 @@
#include "rtc-test.h"
-#define RTC_PERIOD_CODE1 13
-#define RTC_PERIOD_CODE2 15
+#define RTC_PERIOD_CODE1 13 /* 8 Hz */
+#define RTC_PERIOD_CODE2 15 /* 2 Hz */
#define RTC_PERIOD_TEST_NR 50
-static void nsleep(int64_t nsecs)
+static uint64_t wait_periodic_interrupt(uint64_t real_time)
{
- const struct timespec val = { .tv_nsec = nsecs };
- nanosleep(&val, NULL);
-}
-
-static void wait_periodic_interrupt(void)
-{
- while (1) {
- if (get_irq(RTC_ISA_IRQ)) {
- break;
- }
-
- /* 1 us.*/
- nsleep(1000);
+ while (!get_irq(RTC_ISA_IRQ)) {
+ real_time = clock_step_next();
}
g_assert((cmos_read(RTC_REG_C) & REG_C_PF) != 0);
+ return real_time;
}
static void periodic_timer(void)
@@ -51,6 +41,8 @@
int i;
int64_t period_clocks, period_time, real_time;
+ real_time = clock_step(0);
+
/* disable all interrupts. */
cmos_write(RTC_REG_B, cmos_read(RTC_REG_B) &
~(REG_B_PIE | REG_B_AIE | REG_B_UIE));
@@ -58,17 +50,13 @@
/* enable periodic interrupt after properly configure the period. */
cmos_write(RTC_REG_B, cmos_read(RTC_REG_B) | REG_B_PIE);
- real_time = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
-
for (i = 0; i < RTC_PERIOD_TEST_NR; i++) {
cmos_write(RTC_REG_A, RTC_PERIOD_CODE1);
- wait_periodic_interrupt();
+ real_time = wait_periodic_interrupt(real_time);
cmos_write(RTC_REG_A, RTC_PERIOD_CODE2);
- wait_periodic_interrupt();
+ real_time = wait_periodic_interrupt(real_time);
}
- real_time = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - real_time;
-
period_clocks = periodic_period_to_clock(RTC_PERIOD_CODE1) +
periodic_period_to_clock(RTC_PERIOD_CODE2);
period_clocks *= RTC_PERIOD_TEST_NR;
@@ -85,7 +73,7 @@
g_test_init(&argc, &argv, NULL);
- s = qtest_start("-rtc clock=host");
+ s = qtest_start("-rtc clock=vm");
qtest_irq_intercept_in(s, "ioapic");
qtest_add_func("/rtc/periodic/interrupt", periodic_timer);
@@ -98,57 +86,3 @@
return ret;
}
Can you send v2 that integrates this in rtc-test.c?
Thanks,
Paolo
