Show HN: Smol machines – subsecond coldstart, portable virtual machines

Re:Show HN: Smol machines – subsecond coldstart, portable vi... by JuniperMesos on Friday April 17, 2026 @06:30PM (#47811282)

What were the biggest challenges in terms of designing the VM to have subsecond start times? And what are the current bottlenecks for deceasing the start time even further?

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Re:Show HN: Smol machines – subsecond coldstart, portable vi... by binsquare on Friday April 17, 2026 @06:42PM (#47811352)

No special programming tricks were used.

Linux was built in the 90s. Hardware improved more than a 1000x. Linux virtual machine startup times stayed relatively the same.

Turns out we kept adding junk to the linux kernel + bootup operations.

So all I did was cut and remove unnecessary parts until it still worked.

This ended up also getting boot up times to under 1s. The kernel changes are the 10 commits I made, you can verify here: https://github.com/smol-machines/libkrunfw

There's probably more fat to cut to be honest.

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