runtime: use QPC for nanotime and time.now on windows/arm
The previous implementation of nanotime and time.now used a time source
that was updated on the system clock tick, which has a maximum
resolution of about 1ms. On 386 and amd64, this time source maps to
the system performance counter, so has much higher resolution.
On ARM, use QueryPerformanceCounter() to get a high resolution timestamp.
Updates #26148
Change-Id: I1abc99baf927a95b472ac05020a7788626c71d08
Reviewed-on: https://go-review.googlesource.com/c/154758
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/runtime/os_windows.go b/src/runtime/os_windows.go
index 9b34589..20fe01c 100644
--- a/src/runtime/os_windows.go
+++ b/src/runtime/os_windows.go
@@ -198,9 +198,12 @@
}
_NtWaitForSingleObject = windowsFindfunc(n32, []byte("NtWaitForSingleObject\000"))
- if windowsFindfunc(n32, []byte("wine_get_version\000")) != nil {
- // running on Wine
- initWine(k32)
+ underWine := windowsFindfunc(n32, []byte("wine_get_version\000")) != nil
+ if underWine || GOARCH == "arm" {
+ initQPC(k32)
+ }
+ if underWine {
+ initWine()
}
}
@@ -357,7 +360,7 @@
return
}
-func initWine(k32 uintptr) {
+func initQPC(k32 uintptr) {
_GetSystemTimeAsFileTime = windowsFindfunc(k32, []byte("GetSystemTimeAsFileTime\000"))
if _GetSystemTimeAsFileTime == nil {
throw("could not find GetSystemTimeAsFileTime() syscall")
@@ -394,7 +397,9 @@
// We have to do it this way (or similar), since multiplying QPC counter by 100 millions overflows
// int64 and resulted time will always be invalid.
qpcMultiplier = int64(timediv(1000000000, qpcFrequency, nil))
+}
+func initWine() {
useQPCTime = 1
}
diff --git a/src/runtime/sys_windows_arm.s b/src/runtime/sys_windows_arm.s
index 60be74b..514dc52 100644
--- a/src/runtime/sys_windows_arm.s
+++ b/src/runtime/sys_windows_arm.s
@@ -487,115 +487,12 @@
MOVW R0, (R0)
RET
-// See http://www.dcl.hpi.uni-potsdam.de/research/WRK/2007/08/getting-os-information-the-kuser_shared_data-structure/
-// Must read hi1, then lo, then hi2. The snapshot is valid if hi1 == hi2.
-#define _INTERRUPT_TIME 0x7ffe0008
-#define _SYSTEM_TIME 0x7ffe0014
-#define time_lo 0
-#define time_hi1 4
-#define time_hi2 8
-
-TEXT runtime·nanotime(SB),NOSPLIT,$0-8
- MOVW $0, R0
- MOVB runtime·useQPCTime(SB), R0
- CMP $0, R0
- BNE useQPC
- MOVW $_INTERRUPT_TIME, R3
-loop:
- MOVW time_hi1(R3), R1
- MOVW time_lo(R3), R0
- MOVW time_hi2(R3), R2
- CMP R1, R2
- BNE loop
-
- // wintime = R1:R0, multiply by 100
- MOVW $100, R2
- MULLU R0, R2, (R4, R3) // R4:R3 = R1:R0 * R2
- MULA R1, R2, R4, R4
-
- // wintime*100 = R4:R3
- MOVW R3, ret_lo+0(FP)
- MOVW R4, ret_hi+4(FP)
- RET
-useQPC:
+TEXT runtime·nanotime(SB),NOSPLIT|NOFRAME,$0-8
B runtime·nanotimeQPC(SB) // tail call
RET
-TEXT time·now(SB),NOSPLIT,$0-20
- MOVW $0, R0
- MOVB runtime·useQPCTime(SB), R0
- CMP $0, R0
- BNE useQPC
- MOVW $_INTERRUPT_TIME, R3
-loop:
- MOVW time_hi1(R3), R1
- MOVW time_lo(R3), R0
- MOVW time_hi2(R3), R2
- CMP R1, R2
- BNE loop
-
- // wintime = R1:R0, multiply by 100
- MOVW $100, R2
- MULLU R0, R2, (R4, R3) // R4:R3 = R1:R0 * R2
- MULA R1, R2, R4, R4
-
- // wintime*100 = R4:R3
- MOVW R3, mono+12(FP)
- MOVW R4, mono+16(FP)
-
- MOVW $_SYSTEM_TIME, R3
-wall:
- MOVW time_hi1(R3), R1
- MOVW time_lo(R3), R0
- MOVW time_hi2(R3), R2
- CMP R1, R2
- BNE wall
-
- // w = R1:R0 in 100ns untis
- // convert to Unix epoch (but still 100ns units)
- #define delta 116444736000000000
- SUB.S $(delta & 0xFFFFFFFF), R0
- SBC $(delta >> 32), R1
-
- // Convert to nSec
- MOVW $100, R2
- MULLU R0, R2, (R4, R3) // R4:R3 = R1:R0 * R2
- MULA R1, R2, R4, R4
- // w = R2:R1 in nSec
- MOVW R3, R1 // R4:R3 -> R2:R1
- MOVW R4, R2
-
- // multiply nanoseconds by reciprocal of 10**9 (scaled by 2**61)
- // to get seconds (96 bit scaled result)
- MOVW $0x89705f41, R3 // 2**61 * 10**-9
- MULLU R1,R3,(R6,R5) // R7:R6:R5 = R2:R1 * R3
- MOVW $0,R7
- MULALU R2,R3,(R7,R6)
-
- // unscale by discarding low 32 bits, shifting the rest by 29
- MOVW R6>>29,R6 // R7:R6 = (R7:R6:R5 >> 61)
- ORR R7<<3,R6
- MOVW R7>>29,R7
-
- // subtract (10**9 * sec) from nsec to get nanosecond remainder
- MOVW $1000000000, R5 // 10**9
- MULLU R6,R5,(R9,R8) // R9:R8 = R7:R6 * R5
- MULA R7,R5,R9,R9
- SUB.S R8,R1 // R2:R1 -= R9:R8
- SBC R9,R2
-
- // because reciprocal was a truncated repeating fraction, quotient
- // may be slightly too small -- adjust to make remainder < 10**9
- CMP R5,R1 // if remainder > 10**9
- SUB.HS R5,R1 // remainder -= 10**9
- ADD.HS $1,R6 // sec += 1
-
- MOVW R6,sec_lo+0(FP)
- MOVW R7,sec_hi+4(FP)
- MOVW R1,nsec+8(FP)
- RET
-useQPC:
- B runtime·nanotimeQPC(SB) // tail call
+TEXT time·now(SB),NOSPLIT|NOFRAME,$0-20
+ B runtime·nowQPC(SB) // tail call
RET
// save_g saves the g register (R10) into thread local memory
