hpc: do away with String, to avoid making a write() syscall per character
From !1598 (comment 218752) (by @nh2):
At some point we probably want to switch this away from
String
entirely, given thathPutStr
floods syscalls by doing onewrite()
syscall for each character.
This is obviously quite inefficient and should be replaced by code that makes as few write()
syscalls as possible.