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- 03 Mar, 2018 1 commit
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Tobias Klauser authored
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/98095Reviewed-by:
Ian Lance Taylor <iant@golang.org> Run-TryBot: Ian Lance Taylor <iant@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>
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- 13 Oct, 2017 1 commit
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Frank Somers authored
This change adds support for accelerating time.Now by using the __vdso_clock_gettime fast-path via the vDSO on linux/386 if it is available. When the vDSO path to the clocks is available, it is typically 5x-10x faster than the syscall path (see benchmark extract below). Two such calls are made for each time.Now() call on most platforms as of go 1.9. - Add vdso_linux_386.go, containing the ELF32 definitions for use by vdso_linux.go, the maximum array size, and the symbols to be located in the vDSO. - Modify runtime.walltime and runtime.nanotime to check for and use the vDSO fast-path if available, or fall back to the existing syscall path. - Reduce the stack reservations for runtime.walltime and runtime.monotime from 32 to 16 bytes. It appears the syscall path actually only needed 8 bytes, but 16 is now needed to cover the syscall and vDSO paths. - Remove clearing DX from the syscall paths as clock_gettime only takes 2 args (BX, CX in syscall calling convention), so there should be no need to clear DX. The included BenchmarkTimeNow was run with -cpu=1 -count=20 on an "Intel(R) Celeron(R) CPU J1900 @ 1.99GHz", comparing released go 1.9.1 vs this change. This shows a gain in performance on linux/386 (6.89x), and that no regression occurred on linux/amd64 due to this change. Kernel: linux/i686, GOOS=linux GOARCH=386 name old time/op new time/op delta TimeNow 978ns ± 0% 142ns ± 0% -85.48% (p=0.000 n=16+20) Kernel: linux/x86_64, GOOS=linux GOARCH=amd64 name old time/op new time/op delta TimeNow 125ns ± 0% 125ns ± 0% ~ (all equal) Gains are more dramatic in virtualized environments, presumably due to the overhead of virtualizing the syscall. Fixes #22190 Change-Id: I2f83ce60cb1b8b310c9ced0706bb463c1b3aedf8 Reviewed-on: https://go-review.googlesource.com/69390 Run-TryBot: Ian Lance Taylor <iant@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by:
Ian Lance Taylor <iant@golang.org>
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