Author: nyan
Date: Sun Oct 31 08:14:52 2010
New Revision: 214591
URL: http://svn.freebsd.org/changeset/base/214591
Log:
MFC: revision 208638
- Add an integer argument to idle to indicate how likely we are to wake
from idle over the next tick.
- Add a new MD routine, cpu_wake_idle() to wakeup idle threads who are
suspended in cpu specific states. This function can fail and cause the
scheduler to fall back to another mechanism (ipi).
- Implement support for mwait in cpu_idle() on i386/amd64 machines that
support it. mwait is a higher performance way to synchronize cpus
as compared to hlt & ipis.
- Allow selecting the idle routine by name via sysctl machdep.idle. This
replaces machdep.cpu_idle_hlt. Only idle routines supported by the
current machine are permitted.
Modified:
stable/8/sys/pc98/pc98/machdep.c
Directory Properties:
stable/8/sys/ (props changed)
stable/8/sys/amd64/include/xen/ (props changed)
stable/8/sys/cddl/contrib/opensolaris/ (props changed)
stable/8/sys/contrib/dev/acpica/ (props changed)
stable/8/sys/contrib/pf/ (props changed)
stable/8/sys/dev/xen/xenpci/ (props changed)
Modified: stable/8/sys/pc98/pc98/machdep.c
==============================================================================
--- stable/8/sys/pc98/pc98/machdep.c Sun Oct 31 08:08:18 2010
(r214590)
+++ stable/8/sys/pc98/pc98/machdep.c Sun Oct 31 08:14:52 2010
(r214591)
@@ -1104,6 +1104,7 @@ cpu_est_clockrate(int cpu_id, uint64_t *
return (0);
}
+
/*
* Shutdown the CPU as much as possible
*/
@@ -1114,70 +1115,177 @@ cpu_halt(void)
__asm__ ("hlt");
}
-/*
- * Hook to idle the CPU when possible. In the SMP case we default to
- * off because a halted cpu will not currently pick up a new thread in the
- * run queue until the next timer tick. If turned on this will result in
- * approximately a 4.2% loss in real time performance in buildworld tests
- * (but improves user and sys times oddly enough), and saves approximately
- * 5% in power consumption on an idle machine (tests w/2xCPU 1.1GHz P3).
- *
- * XXX we need to have a cpu mask of idle cpus and generate an IPI or
- * otherwise generate some sort of interrupt to wake up cpus sitting in HLT.
- * Then we can have our cake and eat it too.
- *
- * XXX I'm turning it on for SMP as well by default for now. It seems to
- * help lock contention somewhat, and this is critical for HTT. -Peter
- */
-static int cpu_idle_hlt = 1;
-TUNABLE_INT("machdep.cpu_idle_hlt", &cpu_idle_hlt);
-SYSCTL_INT(_machdep, OID_AUTO, cpu_idle_hlt, CTLFLAG_RW,
- &cpu_idle_hlt, 0, "Idle loop HLT enable");
-
static void
-cpu_idle_default(void)
+cpu_idle_hlt(int busy)
{
/*
- * we must absolutely guarentee that hlt is the
- * absolute next instruction after sti or we
- * introduce a timing window.
+ * we must absolutely guarentee that hlt is the next instruction
+ * after sti or we introduce a timing window.
*/
- __asm __volatile("sti; hlt");
+ disable_intr();
+ if (sched_runnable())
+ enable_intr();
+ else
+ __asm __volatile("sti; hlt");
}
-/*
- * Note that we have to be careful here to avoid a race between checking
- * sched_runnable() and actually halting. If we don't do this, we may waste
- * the time between calling hlt and the next interrupt even though there
- * is a runnable process.
- */
+static void
+cpu_idle_spin(int busy)
+{
+ return;
+}
+
+void (*cpu_idle_fn)(int) = cpu_idle_hlt;
+
void
cpu_idle(int busy)
{
-
-#ifdef SMP
+#if defined(SMP)
if (mp_grab_cpu_hlt())
return;
#endif
+ cpu_idle_fn(busy);
+}
+
+/*
+ * mwait cpu power states. Lower 4 bits are sub-states.
+ */
+#define MWAIT_C0 0xf0
+#define MWAIT_C1 0x00
+#define MWAIT_C2 0x10
+#define MWAIT_C3 0x20
+#define MWAIT_C4 0x30
+
+#define MWAIT_DISABLED 0x0
+#define MWAIT_WOKEN 0x1
+#define MWAIT_WAITING 0x2
+
+static void
+cpu_idle_mwait(int busy)
+{
+ int *mwait;
- if (cpu_idle_hlt) {
- disable_intr();
- if (sched_runnable())
- enable_intr();
- else
- (*cpu_idle_hook)();
+ mwait = (int *)PCPU_PTR(monitorbuf);
+ *mwait = MWAIT_WAITING;
+ if (sched_runnable())
+ return;
+ cpu_monitor(mwait, 0, 0);
+ if (*mwait == MWAIT_WAITING)
+ cpu_mwait(0, MWAIT_C1);
+}
+
+static void
+cpu_idle_mwait_hlt(int busy)
+{
+ int *mwait;
+
+ mwait = (int *)PCPU_PTR(monitorbuf);
+ if (busy == 0) {
+ *mwait = MWAIT_DISABLED;
+ cpu_idle_hlt(busy);
+ return;
}
+ *mwait = MWAIT_WAITING;
+ if (sched_runnable())
+ return;
+ cpu_monitor(mwait, 0, 0);
+ if (*mwait == MWAIT_WAITING)
+ cpu_mwait(0, MWAIT_C1);
}
int
cpu_idle_wakeup(int cpu)
{
+ struct pcpu *pcpu;
+ int *mwait;
- return (0);
+ if (cpu_idle_fn == cpu_idle_spin)
+ return (1);
+ if (cpu_idle_fn != cpu_idle_mwait && cpu_idle_fn != cpu_idle_mwait_hlt)
+ return (0);
+ pcpu = pcpu_find(cpu);
+ mwait = (int *)pcpu->pc_monitorbuf;
+ /*
+ * This doesn't need to be atomic since missing the race will
+ * simply result in unnecessary IPIs.
+ */
+ if (cpu_idle_fn == cpu_idle_mwait_hlt && *mwait == MWAIT_DISABLED)
+ return (0);
+ *mwait = MWAIT_WOKEN;
+
+ return (1);
+}
+
+/*
+ * Ordered by speed/power consumption.
+ */
+struct {
+ void *id_fn;
+ char *id_name;
+} idle_tbl[] = {
+ { cpu_idle_spin, "spin" },
+ { cpu_idle_mwait, "mwait" },
+ { cpu_idle_mwait_hlt, "mwait_hlt" },
+ { cpu_idle_hlt, "hlt" },
+ { NULL, NULL }
+};
+
+static int
+idle_sysctl_available(SYSCTL_HANDLER_ARGS)
+{
+ char *avail, *p;
+ int error;
+ int i;
+
+ avail = malloc(256, M_TEMP, M_WAITOK);
+ p = avail;
+ for (i = 0; idle_tbl[i].id_name != NULL; i++) {
+ if (strstr(idle_tbl[i].id_name, "mwait") &&
+ (cpu_feature2 & CPUID2_MON) == 0)
+ continue;
+ p += sprintf(p, "%s, ", idle_tbl[i].id_name);
+ }
+ error = sysctl_handle_string(oidp, avail, 0, req);
+ free(avail, M_TEMP);
+ return (error);
}
-/* Other subsystems (e.g., ACPI) can hook this later. */
-void (*cpu_idle_hook)(void) = cpu_idle_default;
+static int
+idle_sysctl(SYSCTL_HANDLER_ARGS)
+{
+ char buf[16];
+ int error;
+ char *p;
+ int i;
+
+ p = "unknown";
+ for (i = 0; idle_tbl[i].id_name != NULL; i++) {
+ if (idle_tbl[i].id_fn == cpu_idle_fn) {
+ p = idle_tbl[i].id_name;
+ break;
+ }
+ }
+ strncpy(buf, p, sizeof(buf));
+ error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
+ if (error != 0 || req->newptr == NULL)
+ return (error);
+ for (i = 0; idle_tbl[i].id_name != NULL; i++) {
+ if (strstr(idle_tbl[i].id_name, "mwait") &&
+ (cpu_feature2 & CPUID2_MON) == 0)
+ continue;
+ if (strcmp(idle_tbl[i].id_name, buf))
+ continue;
+ cpu_idle_fn = idle_tbl[i].id_fn;
+ return (0);
+ }
+ return (EINVAL);
+}
+
+SYSCTL_PROC(_machdep, OID_AUTO, idle_available, CTLTYPE_STRING | CTLFLAG_RD,
+ 0, 0, idle_sysctl_available, "A", "list of available idle functions");
+
+SYSCTL_PROC(_machdep, OID_AUTO, idle, CTLTYPE_STRING | CTLFLAG_RW, 0, 0,
+ idle_sysctl, "A", "currently selected idle function");
/*
* Reset registers to default values on exec.
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