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| author | Tobias Klauser <tklauser@distanz.ch> | 2018-03-02 11:27:15 +0100 |
|---|---|---|
| committer | Tobias Klauser <tobias.klauser@gmail.com> | 2018-03-03 12:12:58 +0000 |
| commit | 51b027116c2c90e7cb938362b0134ff710fea54e (patch) | |
| tree | 773d74d9a111aea28051bb7ef218675d44fce97e /src/runtime/sys_linux_arm.s | |
| parent | c69f60d0715a836b739b34a92a56c1f7d29485a6 (diff) | |
| download | go-51b027116c2c90e7cb938362b0134ff710fea54e.tar.gz go-51b027116c2c90e7cb938362b0134ff710fea54e.zip | |
runtime: use vDSO for clock_gettime on linux/arm
Use the __vdso_clock_gettime fast path via the vDSO on linux/arm to
speed up nanotime and walltime. This results in the following
performance improvement for time.Now on a RaspberryPi 3 (running
32bit Raspbian, i.e. GOOS=linux/GOARCH=arm):
name old time/op new time/op delta
TimeNow 0.99µs ± 0% 0.39µs ± 1% -60.74% (p=0.000 n=12+20)
Change-Id: I3598278a6c88d7f6a6ce66c56b9d25f9dd2f4c9a
Reviewed-on: https://go-review.googlesource.com/98095
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Diffstat (limited to 'src/runtime/sys_linux_arm.s')
| -rw-r--r-- | src/runtime/sys_linux_arm.s | 88 |
1 files changed, 75 insertions, 13 deletions
diff --git a/src/runtime/sys_linux_arm.s b/src/runtime/sys_linux_arm.s index ef72ae0308..39046bb5c5 100644 --- a/src/runtime/sys_linux_arm.s +++ b/src/runtime/sys_linux_arm.s @@ -10,6 +10,9 @@ #include "go_tls.h" #include "textflag.h" +#define CLOCK_REALTIME 0 +#define CLOCK_MONOTONIC 1 + // for EABI, as we don't support OABI #define SYS_BASE 0x0 @@ -209,31 +212,90 @@ TEXT runtime·mincore(SB),NOSPLIT,$0 MOVW R0, ret+12(FP) RET -TEXT runtime·walltime(SB), NOSPLIT, $32 - MOVW $0, R0 // CLOCK_REALTIME - MOVW $8(R13), R1 // timespec +TEXT runtime·walltime(SB),NOSPLIT,$0-12 + // We don't know how much stack space the VDSO code will need, + // so switch to g0. + + // Save old SP. Use R13 instead of SP to avoid linker rewriting the offsets. + MOVW R13, R4 // R4 is unchanged by C code. + + MOVW g_m(g), R1 + MOVW m_curg(R1), R0 + + CMP R1, R0 // Only switch if on curg. + B.NE noswitch + + MOVW m_g0(R1), R0 + MOVW (g_sched+gobuf_sp)(R0), R13 // Set SP to g0 stack + +noswitch: + SUB $24, R13 // Space for results + BIC $0x7, R13 // Align for C code + + MOVW $CLOCK_REALTIME, R0 + MOVW $8(R13), R1 // timespec + MOVW runtime·__vdso_clock_gettime_sym(SB), R11 + CMP $0, R11 + B.EQ fallback + + BL (R11) + JMP finish + +fallback: MOVW $SYS_clock_gettime, R7 SWI $0 - + +finish: MOVW 8(R13), R0 // sec MOVW 12(R13), R2 // nsec - + + MOVW R4, R13 // Restore real SP + MOVW R0, sec_lo+0(FP) MOVW $0, R1 MOVW R1, sec_hi+4(FP) MOVW R2, nsec+8(FP) - RET + RET // int64 nanotime(void) -TEXT runtime·nanotime(SB),NOSPLIT,$32 - MOVW $1, R0 // CLOCK_MONOTONIC - MOVW $8(R13), R1 // timespec +TEXT runtime·nanotime(SB),NOSPLIT,$0-8 + // Switch to g0 stack. See comment above in runtime·walltime. + + // Save old SP. Use R13 instead of SP to avoid linker rewriting the offsets. + MOVW R13, R4 // R4 is unchanged by C code. + + MOVW g_m(g), R1 + MOVW m_curg(R1), R0 + + CMP R1, R0 // Only switch if on curg. + B.NE noswitch + + MOVW m_g0(R1), R0 + MOVW (g_sched+gobuf_sp)(R0), R13 // Set SP to g0 stack + +noswitch: + SUB $24, R13 // Space for results + BIC $0x7, R13 // Align for C code + + MOVW $CLOCK_MONOTONIC, R0 + MOVW $8(R13), R1 // timespec + MOVW runtime·__vdso_clock_gettime_sym(SB), R11 + CMP $0, R11 + B.EQ fallback + + BL (R11) + JMP finish + +fallback: MOVW $SYS_clock_gettime, R7 SWI $0 - - MOVW 8(R13), R0 // sec - MOVW 12(R13), R2 // nsec - + +finish: + MOVW 8(R13), R0 // sec + MOVW 12(R13), R2 // nsec + + MOVW R4, R13 // Restore real SP + MOVW $1000000000, R3 MULLU R0, R3, (R1, R0) MOVW $0, R4 |