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MonotonicCoarse provides a coarse monotonic time. On some platforms, it is implemented in assembly, which lets us do much less work than time.Now, which gets a high precision monotonic time and a high precision wall time. The assembly code is tied to a particular Go release because it reaches into the Go internals in order to switch to the system stack for the vdso call. On my darwin/arm64 machine, there is no perf difference. On my linux/amd64 machine, MonotonicCoarse is 5x faster (50ns -> 10ns). On my linux/arm64 VM, MonotonicCoarse is 16x faster (64ns -> 4ns). We could also use this in the rate limiter and magicsock, which are two other uses of time.Now that show up in the CPU pprof when doing throughput benchmarking. Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
17 lines
478 B
Go
17 lines
478 B
Go
// +build !go1.16 go1.17 !linux !amd64,!arm64
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package tstime
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import "time"
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var referenceTime = time.Now()
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// MonotonicCoarse returns the number of monotonic seconds elapsed
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// since an unspecified starting point, at low precision.
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// It is only meaningful when compared to the
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// result of previous MonotonicCoarse calls.
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// On some platforms, MonotonicCoarse is much faster than time.Now.
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func MonotonicCoarse() int64 {
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return int64(time.Since(referenceTime).Seconds())
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}
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