runtime: fast clock_gettime call on FreeBSD
Use AT_TIMEKEEP ELF aux entry to access a kernel mapped ring of timehands structs.
The timehands are updated by the kernel periodically, but for accurate measure the
timecounter still needs to be queried.
Currently the fast path is used only when kern.timecounter.hardware==TSC-low
or kern.timecounter.hardware=='ARM MPCore Timecounter',
other timecounters revert back to regular system call.
TODO: add support for HPET timecounter on 386/amd64.
Change-Id: I321ca4e92be63ba21a2574b758ef5c1e729086ad
Reviewed-on: https://go-review.googlesource.com/93156
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/src/runtime/defs_freebsd_arm.go b/src/runtime/defs_freebsd_arm.go
index 71684fe..7b8f0d99 100644
--- a/src/runtime/defs_freebsd_arm.go
+++ b/src/runtime/defs_freebsd_arm.go
@@ -32,6 +32,7 @@
_SA_ONSTACK = 0x1
_CLOCK_MONOTONIC = 0x4
+ _CLOCK_REALTIME = 0x0
_UMTX_OP_WAIT_UINT = 0xb
_UMTX_OP_WAIT_UINT_PRIVATE = 0xf
@@ -194,3 +195,34 @@
data int32
udata *byte
}
+
+type bintime struct {
+ sec int64
+ frac uint64
+}
+
+type vdsoTimehands struct {
+ algo uint32
+ gen uint32
+ scale uint64
+ offset_count uint32
+ counter_mask uint32
+ offset bintime
+ boottime bintime
+ physical uint32
+ res [7]uint32
+}
+
+type vdsoTimekeep struct {
+ ver uint32
+ enabled uint32
+ current uint32
+ pad_cgo_0 [4]byte
+}
+
+const (
+ _VDSO_TK_VER_CURR = 0x1
+
+ vdsoTimehandsSize = 0x58
+ vdsoTimekeepSize = 0x10
+)
