pc/pc64: bring up ap's one after another, use idlehands() while waiting for thunderbirdsarego

when testing in qemu, launching each ap became slower and slower
because all the ap's where spinning in syncclock() waiting for
cpu0 to update its mach0->tscticks, which happens only much later
after all cpu's have been started up.

now we wait for each cpu to do its timer callibration and
manually update our tscticks while we wait and each cpu will
not spin but halt while waiting for active.thunderbirdsarego.
this reduces the system load and noise for timer callibration
and makes the mp startup linear with regard to the number of
cores.

1 files changed, 12 insertions, 3 deletions

diff --git a/sys/src/9/pc/mp.c b/sys/src/9/pc/mp.c
index e937c9391..ba341c5ca 100644
--- a/sys/src/9/pc/mp.c
+++ b/sys/src/9/pc/mp.c
@@ -196,9 +196,7 @@ mpinit(void)
 		ncpu = MAXMACH;
 	memmove((void*)APBOOTSTRAP, apbootstrap, sizeof(apbootstrap));
 	for(i=0; i<nelem(mpapic); i++){
-		if((apic = mpapic[i]) == nil)
-			continue;
-		if(apic->machno >= MAXMACH)
+		if((apic = mpapic[i]) == nil || apic->machno == 0 || apic->machno >= MAXMACH)
 			continue;
 		if(ncpu <= 1)
 			break;
@@ -206,6 +204,17 @@ mpinit(void)
 			mpstartap(apic);
 			conf.nmach++;
 			ncpu--;
+
+			if(!apic->online){
+				print("LAPIC%d: cpu%d did not startup\n", i, apic->machno);
+				continue;
+			}
+
+			/* update tscticks for ap's syncclock() */
+			while(!active.machs[apic->machno]){
+				if(arch->fastclock == tscticks)
+					cycles(&m->tscticks);
+			}
 		}
 	}