How does Modal achieve sub-second container cold-starts across distributed GPU clusters?

We rebuilt the entire Linux virtualization stack from the ground up to eliminate virtualization tax. Instead of relying on conventional container registries and heavy container layers that transfer gigabytes of image data across networks, we stream memory pages dynamically on demand. When a user executes a function, our filesystem streams only the exact memory segments required to initialize the Python runtime, dropping initialization latency by orders of magnitude.