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runtime: add support for VDSO on ppc64x for use in walltime/nanotime

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This change adds support for VDSO on ppc64x, making it possible to
avoid a syscall in walltime and nanotime.

BenchmarkClockVDSOAndFallbackPaths/vDSO-192             20000000    66.0 ns/op
BenchmarkClockVDSOAndFallbackPaths/Fallback-192          1000000    1456 ns/op

Change-Id: I3373bd804b6f122961de3ae9d034e6ccf35748e6
Reviewed-on: https://go-review.googlesource.com/131135
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
This commit is contained in:
Carlos Eduardo Seo 2018-08-23 20:16:19 -03:00 committed by Lynn Boger
parent 8359b5e134
commit dbd8af7472
7 changed files with 118 additions and 16 deletions
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2
src/runtime/os_linux_novdso.go
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@ -3,7 +3,7 @@
// license that can be found in the LICENSE file.
// +build linux
// +build !386,!amd64,!arm,!arm64
// +build !386,!amd64,!arm,!arm64,!ppc64,!ppc64le
package runtime

94
src/runtime/sys_linux_ppc64x.s
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@ -154,21 +154,87 @@ TEXT runtime·mincore(SB),NOSPLIT|NOFRAME,$0-28
// func walltime() (sec int64, nsec int32)
TEXT runtime·walltime(SB),NOSPLIT,$16
MOVD $0, R3 // CLOCK_REALTIME
MOVD $0(R1), R4
SYSCALL $SYS_clock_gettime
MOVD 0(R1), R3 // sec
MOVD 8(R1), R5 // nsec
MOVD R1, R15 // R15 is unchanged by C code
MOVD g_m(g), R21 // R21 = m
MOVD $0, R3 // CLOCK_REALTIME
MOVD runtime·vdsoClockgettimeSym(SB), R12 // Check for VDSO availability
CMP R12, R0
BEQ fallback
// Set vdsoPC and vdsoSP for SIGPROF traceback.
MOVD LR, R14
MOVD R14, m_vdsoPC(R21)
MOVD R15, m_vdsoSP(R21)
MOVD m_curg(R21), R6
CMP g, R6
BNE noswitch
MOVD m_g0(R21), R7
MOVD (g_sched+gobuf_sp)(R7), R1 // Set SP to g0 stack
noswitch:
SUB $16, R1 // Space for results
RLDICR $0, R1, $59, R1 // Align for C code
MOVD R12, CTR
MOVD R1, R4
BL (CTR) // Call from VDSO
MOVD $0, R0 // Restore R0
MOVD R0, m_vdsoSP(R21) // Clear vdsoSP
MOVD 0(R1), R3 // sec
MOVD 8(R1), R5 // nsec
MOVD R15, R1 // Restore SP
finish:
MOVD R3, sec+0(FP)
MOVW R5, nsec+8(FP)
RET
// Syscall fallback
fallback:
ADD $32, R1, R4
SYSCALL $SYS_clock_gettime
MOVD 32(R1), R3
MOVD 40(R1), R5
JMP finish
TEXT runtime·nanotime(SB),NOSPLIT,$16
MOVW $1, R3 // CLOCK_MONOTONIC
MOVD $0(R1), R4
SYSCALL $SYS_clock_gettime
MOVD 0(R1), R3 // sec
MOVD 8(R1), R5 // nsec
MOVD $1, R3 // CLOCK_MONOTONIC
MOVD R1, R15 // R15 is unchanged by C code
MOVD g_m(g), R21 // R21 = m
MOVD runtime·vdsoClockgettimeSym(SB), R12 // Check for VDSO availability
CMP R12, R0
BEQ fallback
// Set vdsoPC and vdsoSP for SIGPROF traceback.
MOVD LR, R14 // R14 is unchanged by C code
MOVD R14, m_vdsoPC(R21)
MOVD R15, m_vdsoSP(R21)
MOVD m_curg(R21), R6
CMP g, R6
BNE noswitch
MOVD m_g0(R21), R7
MOVD (g_sched+gobuf_sp)(R7), R1 // Set SP to g0 stack
noswitch:
SUB $16, R1 // Space for results
RLDICR $0, R1, $59, R1 // Align for C code
MOVD R12, CTR
MOVD R1, R4
BL (CTR) // Call from VDSO
MOVD $0, R0 // Restore R0
MOVD $0, m_vdsoSP(R21) // Clear vdsoSP
MOVD 0(R1), R3 // sec
MOVD 8(R1), R5 // nsec
MOVD R15, R1 // Restore SP
finish:
// sec is in R3, nsec in R5
// return nsec in R3
MOVD $1000000000, R4
@ -177,6 +243,14 @@ TEXT runtime·nanotime(SB),NOSPLIT,$16
MOVD R3, ret+0(FP)
RET
// Syscall fallback
fallback:
ADD $32, R1, R4
SYSCALL $SYS_clock_gettime
MOVD 32(R1), R3
MOVD 48(R1), R5
JMP finish
TEXT runtime·rtsigprocmask(SB),NOSPLIT|NOFRAME,$0-28
MOVW how+0(FP), R3
MOVD new+8(FP), R4

2
src/runtime/vdso_elf64.go
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@ -3,7 +3,7 @@
// license that can be found in the LICENSE file.
// +build linux
// +build amd64 arm64
// +build amd64 arm64 ppc64 ppc64le
package runtime

2
src/runtime/vdso_in_none.go
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@ -2,7 +2,7 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build linux,!386,!amd64,!arm,!arm64 !linux
// +build linux,!386,!amd64,!arm,!arm64,!ppc64,!ppc64le !linux
package runtime

7
src/runtime/vdso_linux.go
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@ -3,7 +3,7 @@
// license that can be found in the LICENSE file.
// +build linux
// +build 386 amd64 arm arm64
// +build 386 amd64 arm arm64 ppc64 ppc64le
package runtime
@ -42,6 +42,8 @@ const (
_STT_FUNC = 2 /* Symbol is a code object */
_STT_NOTYPE = 0 /* Symbol type is not specified */
_STB_GLOBAL = 1 /* Global symbol */
_STB_WEAK = 2 /* Weak symbol */
@ -212,7 +214,8 @@ func vdsoParseSymbols(info *vdsoInfo, version int32) {
sym := &info.symtab[symIndex]
typ := _ELF_ST_TYPE(sym.st_info)
bind := _ELF_ST_BIND(sym.st_info)
if typ != _STT_FUNC || bind != _STB_GLOBAL && bind != _STB_WEAK || sym.st_shndx == _SHN_UNDEF {
// On ppc64x, VDSO functions are of type _STT_NOTYPE.
if typ != _STT_FUNC && typ != _STT_NOTYPE || bind != _STB_GLOBAL && bind != _STB_WEAK || sym.st_shndx == _SHN_UNDEF {
return false
}
if k.name != gostringnocopy(&info.symstrings[sym.st_name]) {

25
src/runtime/vdso_linux_ppc64x.go Normal file
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@ -0,0 +1,25 @@
// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build linux
// +build ppc64 ppc64le
package runtime
const (
// vdsoArrayMax is the byte-size of a maximally sized array on this architecture.
// See cmd/compile/internal/ppc64/galign.go arch.MAXWIDTH initialization.
vdsoArrayMax = 1<<50 - 1
)
var vdsoLinuxVersion = vdsoVersionKey{"LINUX_2.6.15", 0x75fcba5}
var vdsoSymbolKeys = []vdsoSymbolKey{
{"__kernel_clock_gettime", 0xb0cd725, 0xdfa941fd, &vdsoClockgettimeSym},
}
// initialize with vsyscall fallbacks
var (
vdsoClockgettimeSym uintptr = 0
)

2
src/runtime/vdso_linux_test.go
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@ -3,7 +3,7 @@
// license that can be found in the LICENSE file.
// +build linux
// +build 386 amd64 arm arm64
// +build 386 amd64 arm arm64 ppc64 ppc64le
package runtime_test