[dpdk-dev] Using DPDK in a multiprocess environment

[Rogers, Gerald]

Etai,

If this doesn’t work, then you will need to change the virtual address
range that is used by DPDK.  By default this is set dynamically, however;
with DPDK 1.6you can change it to any region in the virtual address space
you want.

The problem you have is what you stated, the secondary process is built
with more shared libraries, which load upon application start, and are
occupying the region that DPDK allocates in the primary for shared regions.

In DPDK version 1.6 there is an option to change the base address.  It is
--base-virtaddr

With this option you can set the base address for where the huge pages are
mapped into the process virtual address space.

This is all implemented within
$DPDK_DIR/lib/librte_eal/linuxapp/eal/eal_memory.c

Gerald





On 4/8/14, 9:07 AM, "elevran" <elevran at gmail.com> wrote:

>Jeff,
>
>Thanks for the quick reply.
>
>I'll see if calling eal_init earlier resolves the problem I'm seeing. I'm
>not sure this will resolve the issue if shared objects are loaded before
>main() starts...
>
>I understand the rationale for having the same mbuf addresses across
>processes. And indeed they're mapped just fine (--virt-addr also gives
>some
>control over the mapping?).
>I was wondering if the same logic applies to the mapping of device PCI
>addresses. Are they shared or passed around between processes in the same
>way?
>
>Thanks again for the quick response,
>Etai
>בתאריך 8 באפר 2014 18:54, "Shaw, Jeffrey B" <jeffrey.b.shaw at intel.com>
>כתב:
>
>> Have you tried calling "rte_eal_init()" closer to the beginning of the
>> program in your secondary process (i.e. the first thing in main())?
>>
>> The same mmap address is required.  The reason is simple, if process A
>> thinks the virtual address of an mbuf is 123, and process B thinks the
>> virtual address of the same mbuf is 456, either process may segmentation
>> fault, accessing mbuf memory that is not actually mapped into the
>>processes
>> address space.
>>
>> Jeff
>>
>> -----Original Message-----
>> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Etai Lev Ran
>> Sent: Tuesday, April 08, 2014 8:13 AM
>> To: dev at dpdk.org
>> Subject: [dpdk-dev] Using DPDK in a multiprocess environment
>>
>> Hi,
>>
>>
>>
>> I'd like to split DPDK application functionality into a setup (primary)
>> process and business logic (secondary) processes.
>>
>> The secondary processes access the hardware queues directly (exclusive
>> queue per process) and not through software rings.
>>
>>
>>
>> I'm running into an initialization problem:
>>
>> -          The primary starts and sets up memory and ports and then
>>goes to
>> sleep waiting for termination signal
>>
>> -          Secondary processes fail when probing the PCI bus for devices
>> (required, otherwise I get 0 ports visible in the secondary)
>>
>>
>>
>> The error is directly related to the secondary failing to get the *same*
>> virtual address for mmap'ing the UIO device fd's.
>>
>> The reason is that the secondary processes has considerably more shared
>> objects loaded and some of these are
>>
>> loaded and mapped into addresses which the primary used to map UIO fd's.
>>
>> The pci_map_resource()  (linuxapp/eal_pci.c) code explicitly requires
>>that
>> the secondary processes get the same mmap'ed
>>
>> address as given to the primary.
>>
>>
>>
>> 1)      Is this behavior (same mmap address) required?
>>
>> 2)      If so, is there a workaround to cause PCI areas of UIO devices
>>to
>> be
>> mapped to the same location in arbitrary processes?
>>
>>
>>
>> The samples work just fine since all primary and secondary processes
>>have
>> similar set and load order for .so's
>>
>>
>>
>> Using  v1.6 on Ubuntu 12.04 64b, ixgbe devices, 1GB hugepages, ASLR
>> disabled.
>>
>>
>>
>> Thanks,
>>
>> Etai
>>
>>
>>
>>