Hi all,
Does DPDK support forking secondary processes after executing rte_eal_init()?
The l2fwd_fork example and at least one application (OpenEM:
https://sourceforge.net/projects/eventmachine/) use this model, and they do so
by fixing up the EAL internals (e.g. manually changing process_type from
primary to secondary) at the start of the child process. This feels like a
hack, and I can't find any documentation describing this model.
Moreover, this approach doesn't appear to be compatible with recent EAL
changes. For instance, the multi-process communication creates a couple handler
threads ("rte_mp_handle" and "rte_mp_async") during EAL initialization. The
child processes won't inherit these threads, and so won't be able to
participate in multi-process comms. This means the reworked memory subsystem
and upcoming device hotplug support
(http://mails.dpdk.org/archives/dev/2018-July/107704.html) won't work with this
fork-after-init model.
This is just one example - there may be other features/subsystems that won't
work. As far as I can tell there is no official stance (though the l2fwd_fork
example implies it's supported, IMO); I think either DPDK should either drop
the example and not support this model, or support it and either document its
limitations or resolve them. This model could be an interesting way to run
multi-process DPDK on an ASLR-enabled system, but supporting this wouldn't be
trivial.
Thanks,
Gage
