runtime: rename ncpu to numCPUStartup

ncpu is the total logical CPU count at startup. It is never updated. For
#73193, we will start using updated CPU counts for updated GOMAXPROCS,
making the ncpu name a bit ambiguous. Change to a less ambiguous name.

While we're at it, give the OS specific lookup functions a common name,
so it can be used outside of osinit later.

For #73193.

Change-Id: I6a6a636cf21cc60de36b211f3c374080849fc667
Reviewed-on: https://go-review.googlesource.com/c/go/+/672277
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>

23 files changed, 54 insertions, 43 deletions

diff --git a/src/runtime/debug.go b/src/runtime/debug.go
index c477e2b9f6..57e9ba8d7d 100644
--- a/src/runtime/debug.go
+++ b/src/runtime/debug.go
@@ -40,7 +40,7 @@ func GOMAXPROCS(n int) int {
 // at process startup. Changes to operating system CPU allocation after
 // process startup are not reflected.
 func NumCPU() int {
-	return int(ncpu)
+	return int(numCPUStartup)
 }
 
 // NumCgoCall returns the number of cgo calls made by the current process.
diff --git a/src/runtime/heapdump.go b/src/runtime/heapdump.go
index 6e6b58edd5..5476035b2e 100644
--- a/src/runtime/heapdump.go
+++ b/src/runtime/heapdump.go
@@ -536,7 +536,7 @@ func dumpparams() {
 	dumpint(uint64(arenaEnd))
 	dumpstr(goarch.GOARCH)
 	dumpstr(buildVersion)
-	dumpint(uint64(ncpu))
+	dumpint(uint64(numCPUStartup))
 }
 
 func itab_callback(tab *itab) {
diff --git a/src/runtime/lock_spinbit.go b/src/runtime/lock_spinbit.go
index f90698a4c9..039ea6f565 100644
--- a/src/runtime/lock_spinbit.go
+++ b/src/runtime/lock_spinbit.go
@@ -175,7 +175,7 @@ func lock2(l *mutex) {
 	// On uniprocessors, no point spinning.
 	// On multiprocessors, spin for mutexActiveSpinCount attempts.
 	spin := 0
-	if ncpu > 1 {
+	if numCPUStartup > 1 {
 		spin = mutexActiveSpinCount
 	}
 
diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index f96dbadd01..84aa1105d8 100644
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -727,10 +727,10 @@ func gcStart(trigger gcTrigger) {
 	systemstack(gcResetMarkState)
 
 	work.stwprocs, work.maxprocs = gomaxprocs, gomaxprocs
-	if work.stwprocs > ncpu {
-		// This is used to compute CPU time of the STW phases,
-		// so it can't be more than ncpu, even if GOMAXPROCS is.
-		work.stwprocs = ncpu
+	if work.stwprocs > numCPUStartup {
+		// This is used to compute CPU time of the STW phases, so it
+		// can't be more than the CPU count, even if GOMAXPROCS is.
+		work.stwprocs = numCPUStartup
 	}
 	work.heap0 = gcController.heapLive.Load()
 	work.pauseNS = 0
diff --git a/src/runtime/os3_solaris.go b/src/runtime/os3_solaris.go
index ded821b2e6..116995e5f6 100644
--- a/src/runtime/os3_solaris.go
+++ b/src/runtime/os3_solaris.go
@@ -137,7 +137,7 @@ func osinit() {
 	// before calling minit on m0.
 	asmcgocall(unsafe.Pointer(abi.FuncPCABI0(miniterrno)), unsafe.Pointer(&libc____errno))
 
-	ncpu = getncpu()
+	numCPUStartup = getCPUCount()
 	if physPageSize == 0 {
 		physPageSize = getPageSize()
 	}
diff --git a/src/runtime/os_aix.go b/src/runtime/os_aix.go
index 1b483c2a7e..3847b7671a 100644
--- a/src/runtime/os_aix.go
+++ b/src/runtime/os_aix.go
@@ -97,10 +97,14 @@ func osinit() {
 	// before calling minit on m0.
 	miniterrno()
 
-	ncpu = int32(sysconf(__SC_NPROCESSORS_ONLN))
+	numCPUStartup = getCPUCount()
 	physPageSize = sysconf(__SC_PAGE_SIZE)
 }
 
+func getCPUCount() int32 {
+	return int32(sysconf(__SC_NPROCESSORS_ONLN))
+}
+
 // newosproc0 is a version of newosproc that can be called before the runtime
 // is initialized.
 //
diff --git a/src/runtime/os_darwin.go b/src/runtime/os_darwin.go
index 6eab3b5c3d..5aef34ff8f 100644
--- a/src/runtime/os_darwin.go
+++ b/src/runtime/os_darwin.go
@@ -144,7 +144,7 @@ func osinit() {
 	// pthread_create delayed until end of goenvs so that we
 	// can look at the environment first.
 
-	ncpu = getncpu()
+	numCPUStartup = getCPUCount()
 	physPageSize = getPageSize()
 
 	osinit_hack()
@@ -168,7 +168,7 @@ const (
 	_HW_PAGESIZE = 7
 )
 
-func getncpu() int32 {
+func getCPUCount() int32 {
 	// Use sysctl to fetch hw.ncpu.
 	mib := [2]uint32{_CTL_HW, _HW_NCPU}
 	out := uint32(0)
diff --git a/src/runtime/os_dragonfly.go b/src/runtime/os_dragonfly.go
index 9b3235084d..e22fd9b42f 100644
--- a/src/runtime/os_dragonfly.go
+++ b/src/runtime/os_dragonfly.go
@@ -78,7 +78,7 @@ const (
 
 var sigset_all = sigset{[4]uint32{^uint32(0), ^uint32(0), ^uint32(0), ^uint32(0)}}
 
-func getncpu() int32 {
+func getCPUCount() int32 {
 	mib := [2]uint32{_CTL_HW, _HW_NCPU}
 	out := uint32(0)
 	nout := unsafe.Sizeof(out)
@@ -174,7 +174,7 @@ func newosproc(mp *m) {
 }
 
 func osinit() {
-	ncpu = getncpu()
+	numCPUStartup = getCPUCount()
 	if physPageSize == 0 {
 		physPageSize = getPageSize()
 	}
diff --git a/src/runtime/os_freebsd.go b/src/runtime/os_freebsd.go
index 1002185f99..ab859cfb47 100644
--- a/src/runtime/os_freebsd.go
+++ b/src/runtime/os_freebsd.go
@@ -91,7 +91,7 @@ const (
 func cpuset_getaffinity(level int, which int, id int64, size int, mask *byte) int32
 
 //go:systemstack
-func getncpu() int32 {
+func getCPUCount() int32 {
 	// Use a large buffer for the CPU mask. We're on the system
 	// stack, so this is fine, and we can't allocate memory for a
 	// dynamically-sized buffer at this point.
@@ -276,7 +276,7 @@ func libpreinit() {
 }
 
 func osinit() {
-	ncpu = getncpu()
+	numCPUStartup = getCPUCount()
 	if physPageSize == 0 {
 		physPageSize = getPageSize()
 	}
diff --git a/src/runtime/os_freebsd_arm.go b/src/runtime/os_freebsd_arm.go
index 5f6bf46798..5a6c60210a 100644
--- a/src/runtime/os_freebsd_arm.go
+++ b/src/runtime/os_freebsd_arm.go
@@ -28,8 +28,9 @@ func checkgoarm() {
 		exit(1)
 	}
 
-	// osinit not called yet, so ncpu not set: must use getncpu directly.
-	if getncpu() > 1 && goarm < 7 {
+	// osinit not called yet, so numCPUStartup not set: must use
+	// getCPUCount directly.
+	if getCPUCount() > 1 && goarm < 7 {
 		print("runtime: this system has multiple CPUs and must use\n")
 		print("atomic synchronization instructions. Recompile using GOARM=7.\n")
 		exit(1)
diff --git a/src/runtime/os_illumos.go b/src/runtime/os_illumos.go
index c3c3e4e6d5..c4bc9fe9c0 100644
--- a/src/runtime/os_illumos.go
+++ b/src/runtime/os_illumos.go
@@ -87,7 +87,7 @@ func getcpucap() uint64 {
 	return capval
 }
 
-func getncpu() int32 {
+func getCPUCount() int32 {
 	n := int32(sysconf(__SC_NPROCESSORS_ONLN))
 	if n < 1 {
 		return 1
diff --git a/src/runtime/os_linux.go b/src/runtime/os_linux.go
index 3071e32202..54f98ef4f8 100644
--- a/src/runtime/os_linux.go
+++ b/src/runtime/os_linux.go
@@ -101,7 +101,7 @@ func futexwakeup(addr *uint32, cnt uint32) {
 	*(*int32)(unsafe.Pointer(uintptr(0x1006))) = 0x1006
 }
 
-func getproccount() int32 {
+func getCPUCount() int32 {
 	// This buffer is huge (8 kB) but we are on the system stack
 	// and there should be plenty of space (64 kB).
 	// Also this is a leaf, so we're not holding up the memory for long.
@@ -354,7 +354,7 @@ func getHugePageSize() uintptr {
 }
 
 func osinit() {
-	ncpu = getproccount()
+	numCPUStartup = getCPUCount()
 	physHugePageSize = getHugePageSize()
 	osArchInit()
 	vgetrandomInit()
diff --git a/src/runtime/os_netbsd.go b/src/runtime/os_netbsd.go
index a06e5febbd..342ede9c53 100644
--- a/src/runtime/os_netbsd.go
+++ b/src/runtime/os_netbsd.go
@@ -120,7 +120,7 @@ func sysctlInt(mib []uint32) (int32, bool) {
 	return out, true
 }
 
-func getncpu() int32 {
+func getCPUCount() int32 {
 	if n, ok := sysctlInt([]uint32{_CTL_HW, _HW_NCPUONLINE}); ok {
 		return int32(n)
 	}
@@ -264,7 +264,7 @@ func netbsdMstart0() {
 }
 
 func osinit() {
-	ncpu = getncpu()
+	numCPUStartup = getCPUCount()
 	if physPageSize == 0 {
 		physPageSize = getPageSize()
 	}
diff --git a/src/runtime/os_netbsd_arm.go b/src/runtime/os_netbsd_arm.go
index 7494a387e3..884b18bdd4 100644
--- a/src/runtime/os_netbsd_arm.go
+++ b/src/runtime/os_netbsd_arm.go
@@ -21,8 +21,9 @@ func lwp_mcontext_init(mc *mcontextt, stk unsafe.Pointer, mp *m, gp *g, fn uintp
 func checkgoarm() {
 	// TODO(minux): FP checks like in os_linux_arm.go.
 
-	// osinit not called yet, so ncpu not set: must use getncpu directly.
-	if getncpu() > 1 && goarm < 7 {
+	// osinit not called yet, so numCPUStartup not set: must use
+	// getCPUCount directly.
+	if getCPUCount() > 1 && goarm < 7 {
 		print("runtime: this system has multiple CPUs and must use\n")
 		print("atomic synchronization instructions. Recompile using GOARM=7.\n")
 		exit(1)
diff --git a/src/runtime/os_only_solaris.go b/src/runtime/os_only_solaris.go
index 0c72500674..aa7b8faf00 100644
--- a/src/runtime/os_only_solaris.go
+++ b/src/runtime/os_only_solaris.go
@@ -8,7 +8,7 @@
 
 package runtime
 
-func getncpu() int32 {
+func getCPUCount() int32 {
 	n := int32(sysconf(__SC_NPROCESSORS_ONLN))
 	if n < 1 {
 		return 1
diff --git a/src/runtime/os_openbsd.go b/src/runtime/os_openbsd.go
index 4ce4c3c58d..02846851d6 100644
--- a/src/runtime/os_openbsd.go
+++ b/src/runtime/os_openbsd.go
@@ -63,7 +63,7 @@ func internal_cpu_sysctlUint64(mib []uint32) (uint64, bool) {
 	return sysctlUint64(mib)
 }
 
-func getncpu() int32 {
+func getCPUCount() int32 {
 	// Try hw.ncpuonline first because hw.ncpu would report a number twice as
 	// high as the actual CPUs running on OpenBSD 6.4 with hyperthreading
 	// disabled (hw.smt=0). See https://golang.org/issue/30127
@@ -135,7 +135,7 @@ func semawakeup(mp *m) {
 }
 
 func osinit() {
-	ncpu = getncpu()
+	numCPUStartup = getCPUCount()
 	physPageSize = getPageSize()
 }
 
diff --git a/src/runtime/os_openbsd_arm.go b/src/runtime/os_openbsd_arm.go
index d5dc8cb479..ba33d4d5bb 100644
--- a/src/runtime/os_openbsd_arm.go
+++ b/src/runtime/os_openbsd_arm.go
@@ -7,8 +7,9 @@ package runtime
 func checkgoarm() {
 	// TODO(minux): FP checks like in os_linux_arm.go.
 
-	// osinit not called yet, so ncpu not set: must use getncpu directly.
-	if getncpu() > 1 && goarm < 7 {
+	// osinit not called yet, so numCPUStartup not set: must use
+	// getCPUCount directly.
+	if getCPUCount() > 1 && goarm < 7 {
 		print("runtime: this system has multiple CPUs and must use\n")
 		print("atomic synchronization instructions. Recompile using GOARM=7.\n")
 		exit(1)
diff --git a/src/runtime/os_plan9.go b/src/runtime/os_plan9.go
index a0ad9060c5..72a8657985 100644
--- a/src/runtime/os_plan9.go
+++ b/src/runtime/os_plan9.go
@@ -230,7 +230,7 @@ func mdestroy(mp *m) {
 
 var sysstat = []byte("/dev/sysstat\x00")
 
-func getproccount() int32 {
+func getCPUCount() int32 {
 	var buf [2048]byte
 	fd := open(&sysstat[0], _OREAD|_OCEXEC, 0)
 	if fd < 0 {
@@ -330,7 +330,7 @@ var (
 func osinit() {
 	physPageSize = getPageSize()
 	initBloc()
-	ncpu = getproccount()
+	numCPUStartup = getCPUCount()
 	getg().m.procid = getpid()
 
 	fd := open(&bintimeDev[0], _OREAD|_OCEXEC, 0)
diff --git a/src/runtime/os_wasm.go b/src/runtime/os_wasm.go
index 8046caf45e..15137cc13f 100644
--- a/src/runtime/os_wasm.go
+++ b/src/runtime/os_wasm.go
@@ -14,10 +14,14 @@ func osinit() {
 	physPageSize = 64 * 1024
 	initBloc()
 	blocMax = uintptr(currentMemory()) * physPageSize // record the initial linear memory size
-	ncpu = 1
+	numCPUStartup = getCPUCount()
 	getg().m.procid = 2
 }
 
+func getCPUCount() int32 {
+	return 1
+}
+
 const _SIGSEGV = 0xb
 
 func sigpanic() {
diff --git a/src/runtime/os_windows.go b/src/runtime/os_windows.go
index a84832e0ce..8f77cd50f8 100644
--- a/src/runtime/os_windows.go
+++ b/src/runtime/os_windows.go
@@ -322,7 +322,7 @@ func monitorSuspendResume() {
 		uintptr(unsafe.Pointer(&params)), uintptr(unsafe.Pointer(&handle)))
 }
 
-func getproccount() int32 {
+func getCPUCount() int32 {
 	var mask, sysmask uintptr
 	ret := stdcall3(_GetProcessAffinityMask, currentProcess, uintptr(unsafe.Pointer(&mask)), uintptr(unsafe.Pointer(&sysmask)))
 	if ret != 0 {
@@ -486,7 +486,7 @@ func osinit() {
 	initSysDirectory()
 	initLongPathSupport()
 
-	ncpu = getproccount()
+	numCPUStartup = getCPUCount()
 
 	physPageSize = getPageSize()
 
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index 5d3e4e4953..f48373fe7c 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -900,7 +900,7 @@ func schedinit() {
 
 	lock(&sched.lock)
 	sched.lastpoll.Store(nanotime())
-	procs := ncpu
+	procs := numCPUStartup
 	if n, ok := strconv.Atoi32(gogetenv("GOMAXPROCS")); ok && n > 0 {
 		procs = n
 	}
@@ -7230,7 +7230,7 @@ func internal_sync_runtime_canSpin(i int) bool {
 	// GOMAXPROCS>1 and there is at least one other running P and local runq is empty.
 	// As opposed to runtime mutex we don't do passive spinning here,
 	// because there can be work on global runq or on other Ps.
-	if i >= active_spin || ncpu <= 1 || gomaxprocs <= sched.npidle.Load()+sched.nmspinning.Load()+1 {
+	if i >= active_spin || numCPUStartup <= 1 || gomaxprocs <= sched.npidle.Load()+sched.nmspinning.Load()+1 {
 		return false
 	}
 	if p := getg().m.p.ptr(); !runqempty(p) {
diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index 920437882d..2c213d0de4 100644
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -1196,12 +1196,12 @@ var isIdleInSynctest = [len(waitReasonStrings)]bool{
 }
 
 var (
-	allm       *m
-	gomaxprocs int32
-	ncpu       int32
-	forcegc    forcegcstate
-	sched      schedt
-	newprocs   int32
+	allm          *m
+	gomaxprocs    int32
+	numCPUStartup int32
+	forcegc       forcegcstate
+	sched         schedt
+	newprocs      int32
 )
 
 var (
diff --git a/src/runtime/vgetrandom_linux.go b/src/runtime/vgetrandom_linux.go
index 6ab12e3c67..8f39f6d3a6 100644
--- a/src/runtime/vgetrandom_linux.go
+++ b/src/runtime/vgetrandom_linux.go
@@ -46,7 +46,7 @@ func vgetrandomInit() {
 func vgetrandomGetState() uintptr {
 	lock(&vgetrandomAlloc.statesLock)
 	if len(vgetrandomAlloc.states) == 0 {
-		num := uintptr(ncpu) // Just a reasonable size hint to start.
+		num := uintptr(numCPUStartup) // Just a reasonable size hint to start.
 		stateSizeCacheAligned := (vgetrandomAlloc.stateSize + cpu.CacheLineSize - 1) &^ (cpu.CacheLineSize - 1)
 		allocSize := (num*stateSizeCacheAligned + physPageSize - 1) &^ (physPageSize - 1)
 		num = (physPageSize / stateSizeCacheAligned) * (allocSize / physPageSize)