Re: [RFC PATCH 00/28] Linux Kernel Library

[Hajime Tazaki <thehajime@gmail.com>]

Hello Octavian,

At Tue,  3 Nov 2015 22:20:31 +0200,
Octavian Purdila wrote:
> 
> 
> Q: How is LKL different from LibOS?
> A: LibOS re-implements high-level kernel APIs for timers, softirqs,
> scheduling, sysctl, SLAB/SLUB, etc. LKL behaves like any arch port,
> implementing the arch level operations requested by the Linux kernel. LKL
> also offers a host interface so that support for multiple hosts can be
> easily implemented.

I review most of code with the help of document and paper (2010).

I think LKL and LibOS are essentially the same thing.

I describe the current differences of both features, which I
believe there are no fundamental ones (i.e., both can
improve by putting some efforts).

- LKL
 (beautiful) arch implementation (I like it)
 fully kbuild compliant
 rich fs support
 host support: POSIX, win, haiku, etc

- LibOS
 existing application integration
 (semi-automated) system call table generation
 multiple process support (via system call proxy)
 various network backends (raw socket, DPDK, netmap, tap)
 symbol namespace separation
 host support: == rump hypercall (POSIX, xen,
   qemu/kvm/baremetal(under development)), ns-3 simulator

# I can't find network support within the current patch but
  there is/will be a certain code that LKL can play with
  networking subsystem.

existing application integration is really important when
you want to configure network stack: since the configuration
of file systems is just a mount(), but configurations of
network stack need much userspace applications like iproute2
(ip, ss, tc) etc, which is not trivial to re-implement.


-- Hajime