DPDK 22.11 Troubleshooting

[Bruce Richardson]

On Mon, May 08, 2023 at 11:26:59PM +0000, Gilbert Carrillo wrote:
> 
> 
> -----Original Message-----
> From: Bruce Richardson <bruce.richardson at intel.com> 
> Sent: Wednesday, May 3, 2023 11:18 AM
> To: Gilbert Carrillo <gcarrillo at ampex.com>
> Cc: dev at dpdk.org
> Subject: Re: DPDK 22.11 Troubleshooting
> 
> On Wed, May 03, 2023 at 04:53:20PM +0000, Gilbert Carrillo wrote:
> > Make static returns an error (see attached).
> > 
> > v/R,
> > Gilbert
> >
> 
> To help investigate this issue, can you perhaps include the text of the full build output when you run "make static". On my system I see libelf listed on the linker flags when I run "make static", and things link properly. I'm wondering how my setup may differ from yours.
> 
> /Bruce
>  
> > -----Original Message-----
> > From: Bruce Richardson <bruce.richardson at intel.com>
> > Sent: Wednesday, May 3, 2023 10:35 AM
> > To: Gilbert Carrillo <gcarrillo at ampex.com>
> > Cc: dev at dpdk.org
> > Subject: Re: DPDK 22.11 Troubleshooting
> > 
> > On Wed, May 03, 2023 at 04:22:05PM +0000, Gilbert Carrillo wrote:
> > > Hi Bruce,
> > > 
> > > Thank you for the response.
> > > 
> > > There is no errors when I run the makefile, however I do see a difference in the programs. I don't believe the makefile is linking all the libraries together as intended.
> > > 
> > > For example, when I run the ethtool sample program and compile it using meson, it works fine and rte_eth_dev_count_avail() returns the correct amount. However, when I compile ethtool with the makefile and run it rte_eth_dev_count_avail() returns 0.
> > > 
> > 
> > Note that by default the meson build will statically link the examples, while the makefile will dynamically load the drivers at runtime. That may explain the difference. Can you try building and running using "make static" rather than just "make".
> > 
> > /Bruce
> 
> Bruce,
> 
> I had multiple versions of DPDK installed and I was linking the wrong one. I was able to compile my application with CMAKE successfully.
> 
> I had one last quick question. I am trying to achieve zero copy DMA from my FPGA to my external buffer. Is this possible? I saw methods such as attaching an mbuf to the external buffer? But I wasn't sure if this was truly zero copy.
> 
Attaching an mbuf to an external buffer would not involve any copy of the
data itself, so should be zero-copy. Each mbuf header contains a buffer
pointer, which normally points just to the end of the header structure, but
which can point to any other location in memory.

/Bruce