On 13-Apr-18 5:40 PM, Bruce Richardson wrote:
On Fri, Apr 13, 2018 at 06:31:21PM +0200, Thomas Monjalon wrote:
It's time to think (again) how we bind devices with kernel modules.
We need to decide how we want to manage hotplugged devices with DPDK.
A bit of history first.
There was some code in DPDK for bind/unbind, but it has been removed
in DPDK 1.7 - http://dpdk.org/commit/5d8751b83
Copy of the commit message (in 2014):
"
The bind/unbind operations should not be handled by the eal.
These operations should be either done outside of dpdk or
inside the PMDs themselves as these are their problems.
"
The question raised at this time (4 years ago) is still under discussion.
Should we manage binding inside or outside DPDK?
Should it be controlled in the application or in the OS base?
As you know, we use dpdk-devbind.py.
This tool lacks two major features:
- persistent configuration
- hotplug
If we consider that the DPDK applications should be able to apply its own
policy to choose the devices to bind, then we need to implement binding
in the PMD (with EAL helpers).
On the other hand, if we consider that it is the system responsibility,
then we could choose systemd/udev and driverctl.
The debate is launched!
Allow me to nail my colours to the mast early! :-)
I believe it's system not application responsibility.
I also believe I have previously explained my reasons for that choice in
some of the previous email threads.
For what it's worth, I tend to agree, if only because writing code for
what is essentially a bunch of read/write/filesystem enumeration in C is
extremely fiddly and error prone :) IMO things like this are better
handled either by scripts, or by tools whose sole purpose is doing
exactly that (or both).
I like having scripts like devbind in DPDK because we can tailor them to
our use cases better, and having them is amenable to automation, but
while I wouldn't be opposed to removing them altogether in favor of some
external tool (systemd/udev/driverctl/whatever), in my humble opinion
moving them back into EAL or even PMD's would be a mistake.
--
Thanks,
Anatoly
