proposal: time.UnixNow() & time.UnixNowMs()

[oguzyildizz]

Hi, in our code we call time.Now() pretty extensively, enough to notice some overhead of calling it. Since we only need the unix timestamp, can we have a way to just get the unix timestamp without allocating unnecessary Time{} structs?

[ianlancetaylor]

I suggest that you use https://pkg.go.dev/golang.org/x/sys/unix?tab=doc#Gettimeofday which calls the gettimeofday system call on a Unix system.

[OneOfOne]

Also if you're fine with using unsafe, you can do something like:

package main

import (
	"fmt"
	"time"
	_ "unsafe"
)

//go:linkname timeNow runtime.walltime
func timeNow() (sec int64, nsec int32)

func main() {
	fmt.Println(timeNow())
	t := time.Now()
	fmt.Println(t.Unix(), t.Nanosecond())
}

[oguzyildizz]

@ianlancetaylor I'm getting 0 result from that, I think it's because of this issue: #38925

@OneOfOne thanks, seems like it's working! anything I should be careful with the unsafe usage?

[ianlancetaylor]

#38925 was fixed, though. What system are you using?

The unsafe suggestion by @OneOfOne is cute but is completely unsafe and unsupported. It will certainly break in some future release of Go.

[oguzyildizz]

I'm using:

go version go1.13.3 darwin/amd64

Just to check, it returns the unix timestamp, right? Not the "time of day" (e.g. seconds since start of day)

[ianlancetaylor]

Yes, unix.Gettimeofday returns a unix.Timeval with a Sec field that is the number of seconds since the epoch, which is the same number that time.Now().Unix() returns.