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From: Stephen Hemminger <stephen@networkplumber.org>
To: Thomas Monjalon <thomas@monjalon.net>
Cc: Bruce Richardson <bruce.richardson@intel.com>, dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH] pci: fix missing pci bus with shared library build
Date: Tue, 23 Jul 2019 11:29:22 -0700	[thread overview]
Message-ID: <20190723112922.52dcb9a9@hermes.lan> (raw)
In-Reply-To: <7229382.2RzrNnEHBx@xps>

On Tue, 23 Jul 2019 09:59:04 +0200
Thomas Monjalon <thomas@monjalon.net> wrote:

> 22/07/2019 20:34, Stephen Hemminger:
> > On Mon, 22 Jul 2019 19:31:08 +0200
> > Thomas Monjalon <thomas@monjalon.net> wrote:
> >   
> > > 22/07/2019 19:13, Stephen Hemminger:  
> > > > Thomas Monjalon <thomas@monjalon.net> wrote:    
> > > > > Are the constructors run on dlopen of the bus driver?    
> > > > 
> > > > Yes, constructors are run on dlopen.
> > > > But application should not have to ask DPDK to dlopen the bus devices.
> > > > 
> > > > The core principle is that dynamic build of DPDK should act the same as old
> > > > statically linked DPDK. Otherwise, the user experience is even worse, and all
> > > > the example documentation is wrong.    
> > > 
> > > OK, this is where I wanted to bring the discussion.
> > > You are arguing against a design which is in DPDK from some early days.
> > > So this is an interesting discussion to have.
> > > Do we want to change the "plugin model" we have?
> > > Or do we want to simply drop this model (dlopen calls)
> > > and replace it with strong dynamic linking?  
> > 
> > I argue that examples should work the same with dynamic linking.
> > This used to work before the break out of the bus model, so it is a bug.  
> 
> The PCI support was part of EAL, yes, but the device drivers
> were plugins and already required the -d option.
> 
> > For distributions, this also matters. Linking with -ldpdk which is a linker
> > script should work.  
> 
> There is no longer this linker script with meson.
> 
> 

Ok, for usability that is a problem.
Requiring user to figure out which DPDK libraries to link with is a serious
waste of time. It should be possible to just link with -ldpdk and
distribution packages and just get the necessary libraries for the application
(no extra rte_foo_bar .so loaded at run time), and the application should
just work.

The idea that the user should link with 20 shared libraries, in the right
order and pass -d flags to eal_init to load the right PMD is user hostile.
It only makes sense if you want to invent yet another layer to manage the
ugly stuff hidden underneath. Think virt-manager versus raw KVM/QEMU.

I know it is hard, and I know not all this will make it into 19.08
but let's try and do better. The DPDK already has a reputation as being
like a super car, (ie unreliable and hard to drive). It doesn't have to be that way.


  reply	other threads:[~2019-07-23 18:29 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-15 23:41 Stephen Hemminger
2019-07-16  0:16 ` Stephen Hemminger
2019-07-16  0:19 ` Stephen Hemminger
2019-07-16  8:46   ` Bruce Richardson
2019-07-16 14:46     ` Stephen Hemminger
2019-07-19 18:11     ` Stephen Hemminger
2019-07-19 20:39     ` Stephen Hemminger
2019-07-19 20:55     ` Stephen Hemminger
2019-07-22  7:38       ` Thomas Monjalon
2019-07-22  9:06         ` Bruce Richardson
2019-07-22 16:43           ` Stephen Hemminger
2019-07-22 17:04             ` Thomas Monjalon
2019-07-22 17:13               ` Stephen Hemminger
2019-07-22 17:31                 ` Thomas Monjalon
2019-07-22 18:34                   ` Stephen Hemminger
2019-07-23  7:59                     ` Thomas Monjalon
2019-07-23 18:29                       ` Stephen Hemminger [this message]
2019-07-23 18:35                         ` Thomas Monjalon
2019-07-22 18:53                   ` Stephen Hemminger
2019-07-23 12:30                     ` Bruce Richardson
2019-07-23 18:11                       ` Stephen Hemminger
2019-07-24  8:56                         ` Bruce Richardson
2019-07-23 18:47                       ` Stephen Hemminger

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