Author: mav
Date: Sat May 2 22:30:33 2009
New Revision: 191760
URL: http://svn.freebsd.org/changeset/base/191760
Log:
Avoid comparing negative signed to positive unsignad values. It was
leading to a bug, when C-state does not decrease on sleep shorter then
declared transition latency. Fixing this deprecates workaround for broken
C-states on some hardware.
By the way, change state selecting logic a bit. Instead of last sleep
time use short-time average of it. Global interrupts rate in system is a
quite random value, to corellate subsequent sleeps so directly.
Modified:
head/sys/dev/acpica/acpi_cpu.c
Modified: head/sys/dev/acpica/acpi_cpu.c
==============================================================================
--- head/sys/dev/acpica/acpi_cpu.c Sat May 2 22:22:00 2009
(r191759)
+++ head/sys/dev/acpica/acpi_cpu.c Sat May 2 22:30:33 2009
(r191760)
@@ -882,43 +882,13 @@ acpi_cpu_idle()
return;
}
- /*
- * If we slept 100 us or more, use the lowest Cx state. Otherwise,
- * find the lowest state that has a latency less than or equal to
- * the length of our last sleep.
- */
- cx_next_idx = sc->cpu_cx_lowest;
- if (sc->cpu_prev_sleep < 100) {
- /*
- * If we sleep too short all the time, this system may not implement
- * C2/3 correctly (i.e. reads return immediately). In this case,
- * back off and use the next higher level.
- * It seems that when you have a dual core cpu (like the Intel Core Duo)
- * that both cores will get out of C3 state as soon as one of them
- * requires it. This breaks the sleep detection logic as the sleep
- * counter is local to each cpu. Disable the sleep logic for now as a
- * workaround if there's more than one CPU. The right fix would probably
- * be to add quirks for system that don't really support C3 state.
- */
- if (mp_ncpus < 2 && sc->cpu_prev_sleep <= 1) {
- sc->cpu_short_slp++;
- if (sc->cpu_short_slp == 1000 && sc->cpu_cx_lowest != 0) {
- if (sc->cpu_non_c3 == sc->cpu_cx_lowest && sc->cpu_non_c3 != 0)
- sc->cpu_non_c3--;
- sc->cpu_cx_lowest--;
- sc->cpu_short_slp = 0;
- device_printf(sc->cpu_dev,
- "too many short sleeps, backing off to C%d\n",
- sc->cpu_cx_lowest + 1);
- }
- } else
- sc->cpu_short_slp = 0;
-
- for (i = sc->cpu_cx_lowest; i >= 0; i--)
- if (sc->cpu_cx_states[i].trans_lat <= sc->cpu_prev_sleep) {
- cx_next_idx = i;
- break;
- }
+ /* Find the lowest state that has small enougth latency. */
+ cx_next_idx = 0;
+ for (i = sc->cpu_cx_lowest; i >= 0; i--) {
+ if (sc->cpu_cx_states[i].trans_lat * 3 <= sc->cpu_prev_sleep) {
+ cx_next_idx = i;
+ break;
+ }
}
/*
@@ -943,10 +913,10 @@ acpi_cpu_idle()
/*
* Execute HLT (or equivalent) and wait for an interrupt. We can't
* calculate the time spent in C1 since the place we wake up is an
- * ISR. Assume we slept one quantum and return.
+ * ISR. Assume we slept half of quantum and return.
*/
if (cx_next->type == ACPI_STATE_C1) {
- sc->cpu_prev_sleep = 1000000 / hz;
+ sc->cpu_prev_sleep = (sc->cpu_prev_sleep * 3 + 500000 / hz) / 4;
acpi_cpu_c1();
return;
}
@@ -989,9 +959,9 @@ acpi_cpu_idle()
}
ACPI_ENABLE_IRQS();
- /* Find the actual time asleep in microseconds, minus overhead. */
+ /* Find the actual time asleep in microseconds. */
end_time = acpi_TimerDelta(end_time, start_time);
- sc->cpu_prev_sleep = PM_USEC(end_time) - cx_next->trans_lat;
+ sc->cpu_prev_sleep = (sc->cpu_prev_sleep * 3 + PM_USEC(end_time)) / 4;
}
/*
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