What is the max number which geth's targetgaslimit option can take?

Question

I want to put lots of data into one transaction in private geth network. What is the max number which geth's targetgaslimit option can take?

Answer 1

Looking at how the flag is set in flags.go:

TargetGasLimitFlag = cli.StringFlag{
    Name:  "targetgaslimit",
    Usage: "Target gas limit sets the artificial target gas floor for the blocks to mine",
    Value: params.GenesisGasLimit.String(),
}

GenesisGasLimit itself is initialised to "million pi" as a big int:

params.GenesisGasLimit = big.NewInt(3141592)

Elsewhere in the code it continues to be handled as a big int. I can't immediately see anywhere in the code that imposes a limit on the value.