[dpdk-dev] NUMA node/socket

[Dmitry Kozlyuk]

2021-07-04 11:28 (UTC+0200), Thomas Monjalon:
> 04/07/2021 10:27, Andrew Rybchenko:
> > On 7/4/21 4:53 AM, Thomas Monjalon wrote:  
> > > 04/07/2021 03:38, Thomas Monjalon:  
> > >> There are some mix between NUMA node and socket IDs in DPDK.
> > >> Examples:
> > >> 	* rte_eth_dev_socket_id() returns the NUMA node.
> > >> 	* rte_malloc use sockets to allocate the memory
> > >>
> > >> Is it critical?  
> > > 
> > > There is a function, implemented for Windows only,
> > > which distinguishes clearly node and socket
> > > but it assumes there is only 1 node per socket:
> > > 
> > > unsigned int
> > > eal_socket_numa_node(unsigned int socket_id)
> > > {
> > >     return cpu_map.sockets[socket_id].node_id;
> > > }
> > > 
> > > Reminder: AMD can be configured to have multiple nodes per socket.
> >
> > Taking the reminder into account the topic definitely
> > requires improvements.
> > 
> > I apologize for my ignorance, but
> > Is socket ID really interesting to anybody in DPDK?  
> 
> I think the socket ID might be interesting for the threads,
> but not for memory or devices.
> 
> > If no, we should just clarify terminology and switch
> > to NUMA node everywhere.  
> 
> I have the same opinion as Andrew.
> If socket ID is required, it could be deduced from the NUMA node
> or from the CPU core.

I agree with renaming too.
Everywhere in DPDK "socket ID" really means "NUMA node".

I don't see how exactly socket ID can be deduced from NUMA node or CPU core
(assuming rte_socket_id becomes rte_numa_node_id), but I also can't imagine
why an app would need it. EAL could use NUMA distance info for better memory
management: currently SOCKET_ID_ANY means "current NUMA node or the first one
with enough memory available" while it could be "or the closest one".