Re:Unicore: A new Unikernel project
by jdboyd on Sunday September 17, 2017 @02:00AM
(#15268428)
If you strip Linux and run your app as PID 1, you will still have context switching between user space and kernel space, which can be fairly expensive (thus the interest in user land TCP/IP stacks). Presumably most unikernels avoid that cost.
[ Parent
| on HN ]
Re:Unicore: A new Unikernel project
by minipci1321 on Sunday September 17, 2017 @03:33AM
(#15268637)
You should clarify your terminology:
-- "context switch" (expensive) is the switch among active (running on this CPU) tasks/threads/processes.
-- switching between kernel and userspace would be "mode switch", much less expensive and of "constant" cost (see, for example, http://blog.tsunanet.net/2010/11/how-long-does-it-take-to-ma...).
Your phrase already carries this contradiction: "__can__ be fairly expensive" points to something depending on what is being executed, rather than a property of the mode switch itself. Then, arguably, the same need of that costly execution should also be present with unikernels?