[Solved] Kernel: preset loops per jiffy

[biangbiangmian]

I want to set lpj to eliminate the calibration step in my kernel boot, but I do not see it in kernel_menuconfig. According to elinux it was added in 2.6.9-rc2. Is it present at all anymore?

[ 0.008272] Calibrating delay loop... 432.53 BogoMIPS (lpj=2162688)

I just want to set lpj to 2162688 for my kernel to skip the calibration step.

[lleachii]

I think you misread.

Unless I misunderstand, or you're running an X86_64 machine, I'm not sure how you'd do this...?

@biangbiangmian

Edit: I just found "Environment variables to set when starting init" is that it?

(Moved to the For Developers section.)

[biangbiangmian]

I think I found it, it's under kernel_menuconfig > kernel hacking > default kernel command string. documentation (search lpj)

[biangbiangmian]

Confirmed!
[ 0.008271] Calibrating delay loop (skipped) preset value.. 432.53 BogoMIPS (lpj=2162688)

[Ansuel]

Why someone would disable this?

[biangbiangmian]

You are not disabling it, you are just pre-setting the value so Linux does not have to calibrate loops per jiffy on every boot. It depends on your clock speed but it can save a small amount of time on every boot. It is as simple as getting your loops per jiffy value from the boot log and setting the lpj parameter in the kernel command string.