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runtime: fast clock_gettime on FreeBSD, split getHPETTimecounter

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Call only initHPETTimecounter on the system stack.
Use O_CLOEXEC flag when opening the HPET device.

FreeBSD 12.3-RELEASE-p2, AMD FX-8300
paulzhol@relic:~/go/src/time % ~/gocode/bin/benchcmp old_hpet.txt new_hpet.txt
benchcmp is deprecated in favor of benchstat: https://pkg.go.dev/golang.org/x/perf/cmd/benchstat
benchmark                   old ns/op     new ns/op     delta
BenchmarkNow-8              1420          1397          -1.62%
BenchmarkNowUnixNano-8      1421          1404          -1.20%
BenchmarkNowUnixMilli-8     1423          1405          -1.26%
BenchmarkNowUnixMicro-8     1423          1404          -1.34%

Update #50947

Change-Id: I553b5427fb0b86d7e070af4516b36326bc0aaf00
Reviewed-on: https://go-review.googlesource.com/c/go/+/391856
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
This commit is contained in:
Yuval Pavel Zholkover 2022-03-11 19:54:08 +02:00 committed by Meng Zhuo
parent a719a78c1b
commit e51b3ae0ee
1 changed files with 28 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

58
src/runtime/vdso_freebsd_x86.go
View File

@ -34,10 +34,8 @@ func (th *vdsoTimehands) getTSCTimecounter() uint32 {
return uint32(tsc)
}
//go:systemstack
//go:nosplit
func (th *vdsoTimehands) getHPETTimecounter() (uint32, bool) {
const digits = "0123456789"
idx := int(th.x86_hpet_idx)
if idx >= len(hpetDevMap) {
return 0, false
@ -45,25 +43,7 @@ func (th *vdsoTimehands) getHPETTimecounter() (uint32, bool) {
p := atomic.Loaduintptr(&hpetDevMap[idx])
if p == 0 {
var devPath [len(hpetDevPath)]byte
copy(devPath[:], hpetDevPath)
devPath[9] = digits[idx]
fd := open(&devPath[0], 0 /* O_RDONLY */, 0)
if fd < 0 {
atomic.Casuintptr(&hpetDevMap[idx], 0, ^uintptr(0))
return 0, false
}
addr, mmapErr := mmap(nil, physPageSize, _PROT_READ, _MAP_SHARED, fd, 0)
closefd(fd)
newP := uintptr(addr)
if mmapErr != 0 {
newP = ^uintptr(0)
}
if !atomic.Casuintptr(&hpetDevMap[idx], 0, newP) && mmapErr == 0 {
munmap(addr, physPageSize)
}
systemstack(func() { initHPETTimecounter(idx) })
p = atomic.Loaduintptr(&hpetDevMap[idx])
}
if p == ^uintptr(0) {
@ -72,20 +52,38 @@ func (th *vdsoTimehands) getHPETTimecounter() (uint32, bool) {
return *(*uint32)(unsafe.Pointer(p + _HPET_MAIN_COUNTER)), true
}
//go:systemstack
func initHPETTimecounter(idx int) {
const digits = "0123456789"
var devPath [len(hpetDevPath)]byte
copy(devPath[:], hpetDevPath)
devPath[9] = digits[idx]
fd := open(&devPath[0], 0 /* O_RDONLY */ |_O_CLOEXEC, 0)
if fd < 0 {
atomic.Casuintptr(&hpetDevMap[idx], 0, ^uintptr(0))
return
}
addr, mmapErr := mmap(nil, physPageSize, _PROT_READ, _MAP_SHARED, fd, 0)
closefd(fd)
newP := uintptr(addr)
if mmapErr != 0 {
newP = ^uintptr(0)
}
if !atomic.Casuintptr(&hpetDevMap[idx], 0, newP) && mmapErr == 0 {
munmap(addr, physPageSize)
}
}
//go:nosplit
func (th *vdsoTimehands) getTimecounter() (uint32, bool) {
switch th.algo {
case _VDSO_TH_ALGO_X86_TSC:
return th.getTSCTimecounter(), true
case _VDSO_TH_ALGO_X86_HPET:
var (
tc uint32
ok bool
)
systemstack(func() {
tc, ok = th.getHPETTimecounter()
})
return tc, ok
return th.getHPETTimecounter()
default:
return 0, false
}