Hi Justin,
Thank you very much for the reply, thank you for taking out some time from
your busy schedule of developing the new things.
I just have a small question, Can I create a child process, I mean can I
do a fork when running inside rump-kernel.
Regards, Santos
On Sun, Apr 20, 2014 at 5:25 AM, Justin Cormack <
[email protected]> wrote:
> On Sat, Apr 19, 2014 at 10:35 AM, Santos Das <[email protected]> wrote:
> > Hi,
> >
> > I am trying to use rump kernel for Nginx. The motivation for me to use
> the
> > TCP stack in user space to achieve higher performance. Not sure if
> someone
> > has already done it ? Any pointers on this would be of much help to us.
>
> I don't think anyone has tried yet...
>
> > Before I start, I have a basic question ? Does the current rump kernel
> > support multiple processes? As you know, in Nginx we have master process
> > which creates several worker process. The master process creates the
> listen
> > socket and all the worker listens to that socket and the synchronization
> is
> > achieved through the mutex.
>
> No, the rump kernel only supports single processes. You can have
> multiple threads. This is one of the reasons I have not really looked
> at Nginx, as it seems to require multiple processes as part of the
> architecture.
>
> > Now, can I link the rump kernel to the main process . Since the worker
> > processes fork from the parent, they will get the linked rump kernel
> library
> > along with it during the fork system call in their process address space.
>
> That is not going to work, as the rump kernel is multithreaded and
> needs to do synchronisations.
>
> > The parent process will open the listen 'socket' (here it is no longer a
> > socket, just a call to the rump kernel socket abstraction) and do a
> > select/epoll/kqueue (again a event loop abstraction). Each forked worker
> > process will inherit this listen 'socket'. The zero copy driver will
> deliver
> > packets to a user space fifo which will result in read activity
> notification
> > in the rump kernel select abstraction (this is no different from a
> typical
> > process of getting a packet on the NIC, servicing a network hardware
> > interrupt and going through the TCP state machine. Only here all that
> > happens in user space and interrupts are replaced by polling the FIFO).
> >
> > Is this supported ? Please let me know if I am wrong in my assumption.
>
> If you can persuade Nginx to work with threads rather than processes,
> or if you can make it run over TCP sockets (so each process has its
> own rump kernel) then this might work.
>
> I would be more inclined to start with a different evented http
> server, maybe based on libev/libuv, rather than Nginx...
>
> >
> > Another thing I dont fully understand is how the rump kernel needs to
> > interface with the real kernel for other system calls. (system calls like
> > gettimeofday(), or fork, setbrk, other timer related calls or file system
> > calls) cannot be serviced by the rump kernel since it is only a library
> and
> > it will need to hand it over to the real kernel for all this.
>
> There are now time and timer calls in the rump kernel. Otherwise if
> you are using the rumprun https://github.com/rumpkernel/rumprun build
> model you can add extra host syscals via emul.c to cover for the
> missing ones.
>
> Justin
>
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