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runtime: allow more CPUs on FreeBSD

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Currently the FreeBSD CPU affinity code assumes that the maximum
GOMAXPROCS is 256, but we just removed that limit.

This commit rewrites the FreeBSD CPU affinity code to raise the CPU
count limit to 65,536, like the Linux CPU affinity code, and to
degrade more gracefully if we do somehow go over that.

Change-Id: Ic4ca7f88bd8b9448aae4dbd43ef21a6c1b8fea63
Reviewed-on: https://go-review.googlesource.com/66291
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Austin Clements 2017-09-26 11:18:37 -04:00
parent e900e275e8
commit a714470cce
1 changed files with 13 additions and 10 deletions
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23
src/runtime/os_freebsd.go
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@ -69,15 +69,19 @@ func sysctlnametomib(name []byte, mib *[_CTL_MAXNAME]uint32) uint32 {
}
const (
_CPU_SETSIZE_MAX = 32 // Limited by _MaxGomaxprocs(256) in runtime2.go.
_CPU_CURRENT_PID = -1 // Current process ID.
)
//go:noescape
func cpuset_getaffinity(level int, which int, id int64, size int, mask *byte) int32
//go:systemstack
func getncpu() int32 {
var mask [_CPU_SETSIZE_MAX]byte
// 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.
const maxCPUs = 64 * 1024
var mask [maxCPUs / 8]byte
var mib [_CTL_MAXNAME]uint32
// According to FreeBSD's /usr/src/sys/kern/kern_cpuset.c,
@ -99,21 +103,20 @@ func getncpu() int32 {
return 1
}
size := maxcpus / _NBBY
ptrsize := uint32(unsafe.Sizeof(uintptr(0)))
if size < ptrsize {
size = ptrsize
maskSize := int(maxcpus+7) / 8
if maskSize < sys.PtrSize {
maskSize = sys.PtrSize
}
if size > _CPU_SETSIZE_MAX {
return 1
if maskSize > len(mask) {
maskSize = len(mask)
}
if cpuset_getaffinity(_CPU_LEVEL_WHICH, _CPU_WHICH_PID, _CPU_CURRENT_PID,
int(size), (*byte)(unsafe.Pointer(&mask[0]))) != 0 {
maskSize, (*byte)(unsafe.Pointer(&mask[0]))) != 0 {
return 1
}
n := int32(0)
for _, v := range mask[:size] {
for _, v := range mask[:maskSize] {
for v != 0 {
n += int32(v & 1)
v >>= 1