Re: [dpdk-dev] propose a solution for mapping same virtual address space to asymmetric processes

["Richardson, Bruce" <bruce.richardson@intel.com>]

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Nissim Nisimov
> Sent: Tuesday, October 13, 2015 4:40 PM
> To: 'dev@dpdk.org'
> Subject: [dpdk-dev] propose a solution for mapping same virtual address
> space to asymmetric processes
> 
> Hi all,
> 
> The below will try to suggest a modification to the initialization of
> Environment Abstraction Layer (AKA EAL) so it will be able to allocate
> memory zones from same virtual memory addresses even if the primary
> process is not similar to the secondary processes.
> 
> Problem:
> The DPDK Primary/Secondary model requires that the exact same hugepage
> memory mappings be present in all applications.
> An issue may occur when the Primary and secondary processes are not
> symmetric in such way that the code has big differences (for example,
> Primary process is a traffic distributer and secondary is a worker).
> The result may be that specific virtual address region in the first
> process won't be available in the second process.
> 
> 
> Suggested solution:
> Map all related rte and uio sections somewhere close to the end of huge
> pages memory (that mean rte_eal_memory_init() should be called before
> rte_config_init() in primary process) According to our observations there
> will be more probability to success when allocating the above sections
> after huge pages section (actually uio is already allocated after the huge
> pages area)
> 
> It solved our problem when trying to work with a primary traffic
> distributer which is a very "light" process and few secondary worker
> processes.
> 
> 
> Please share your thoughts on this before I will try to commit our patch
> for review
> 
> Thanks,
> Nissim

Hi,

out of interest, have you tried fixing the issue using the "--base-virtaddr" EAL flag to hint a base address to the primary process? It was put into the code some time ago to help solve exactly this problem.

/Bruce