get boot time each time cost too much cpu

[hz-kelpie]

i use process.NewProcess(pid) 1000 processes per second
but common.BootTimeWithContext() runs every time,it depends on syscall.Syscall, it's blocked
maybe there's some way I don't know to cache the Process.starttime?
thx~

[Lomanic]

We can't cache host.BootTime as it can jump if time gets adjusted (like with ntpd)

Tested on a Raspberry Pi

pi@raspberrypi:~ $ grep btime /proc/stat
btime 1621271964
pi@raspberrypi:~ $ sudo systemctl disable systemd-timesyncd
pi@raspberrypi:~ $ sudo systemctl stop systemd-timesyncd
pi@raspberrypi:~ $ sudo systemctl disable fake-hwclock.service
pi@raspberrypi:~ $ sudo systemctl stop fake-hwclock.service
pi@raspberrypi:~ $ sudo reboot
# after reboot
pi@raspberrypi:~ $ grep btime /proc/stat
btime 1550139115
pi@raspberrypi:~ $ sudo systemctl enable systemd-timesyncd
pi@raspberrypi:~ $ sudo systemctl start systemd-timesyncd
pi@raspberrypi:~ $ grep btime /proc/stat
btime 1621272415
# btime jumped

See also #857/#837

[hz-kelpie]

Thanks for your response, I think you are right
can i skip the step getting boot time , It's bit of a waste of time

[hz-kelpie]

Because this method has a lock
I can't reduce the CPU even with concurrency

[ghost]

Meet the same question. "process.NewProcessWithContext()" blocked in my situation when using pprof to monitor go routine stacks. And I found another problem, "process.NewProcessWithContext()" seems not using context (1th param) as a timeout control threshold. Then block may happen.

[cforce]

@hz-kelpie Is this unnecessary step getting boot time meanwhile dropped from the codebase and merged? Can this issue then get solved?