Re: [dpdk-dev] Cannot mmap device resource in DPDK 1.7.0 multi-process/multi-thread

["Mario Gianni" <m.gianni@engineer.com>]

Hi Bruce, 
thank you for your answer, adding cores to the primary mask didn't help, instead it helped manually passing the --base-virtaddr parameter, setting it to the first value of Virtual Area that EAL finds when it starts the primary process.
 
Honestly I don't understand why it works in this way, in the experimental phase this could be a patch, but in the final program I have to automate this process, do you have any suggestions?
For example is there a way to find the virtual area before starting the primary process?
 
Mario
 

Sent: Friday, October 24, 2014 at 2:08 PM
From: "Bruce Richardson" <bruce.richardson@intel.com>
To: "Mario Gianni" <m.gianni@engineer.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] Cannot mmap device resource in DPDK 1.7.0 multi-process/multi-thread
On Fri, Oct 24, 2014 at 01:21:08PM +0200, Mario Gianni wrote:
> Hi all, I have a problem since I updated to 1.7.0 version,
> I got a multi-process, multi-threaded application,
> In my application first I launch a master process, then I launch a secondary process with multiple threads in it
> Well, when the number of lcores reserved for the secondary process exceeds a certain number (eg. 4) i got an error in rte_eal_init() on the secondary process when it tries to map PCI memory:
>
> EAL: pci_map_resource(): cannot mmap(12, 0x7ffff2e96000, 0x800000, 0x1000): Success (0x7ffff559b000)
> EAL: Cannot mmap device resource
> EAL: Error - exiting with code: 1
> Cause: Requested device 0000:01:00.0 cannot be used
>
> Can you help me?

This could be because the additional memory/stack space used by the pthreads
for the cores in the secondary process is overlapping the space used in the
primary process for hugepage or device memory. You could perhaps try adding
a few cores to the primary process's coremask (and not using those cores)
and see if it helps things.
Alternatively there is a base-virtaddr parameter that can be passed to the
primary process to try and adjust the starting address for it mapping
memory. If you look at where it starts mapping memory right now, and then
try hinting to it to maps the pages at a slightly higher or lower address
and see if it helps.

/Bruce