Re: [dpdk-stable] [PATCH] bus/pci: fix selection of default device NUMA node

[Olivier Matz <olivier.matz@6wind.com>]

+CC David

On Tue, Oct 26, 2021 at 11:17:08AM +0200, Olivier Matz wrote:
> On Tue, Oct 26, 2021 at 11:06:10AM +0200, Houssem Bouhlel wrote:
> > There can be dev binding issue when no hugepages
> > are allocated for socket 0.
> > To avoid this, set device numa node value based on
> > the first lcore instead of 0.
> > 
> > Fixes: 831dba47bd36 ("bus/vmbus: add Hyper-V virtual bus support")
> 
> Sorry, the Fixes line is wrong. This is the correct one:
> Fixes: 8a04cb612589 ("pci: set default numa node for broken systems")
> 
> > Cc: stable@dpdk.org
> > 
> > Signed-off-by: Houssem Bouhlel <houssem.bouhlel@6wind.com>
> > Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> > ---
> >  drivers/bus/pci/pci_common.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/bus/pci/pci_common.c b/drivers/bus/pci/pci_common.c
> > index f8fff2c98ebf..c70ab2373c79 100644
> > --- a/drivers/bus/pci/pci_common.c
> > +++ b/drivers/bus/pci/pci_common.c
> > @@ -166,6 +166,7 @@ rte_pci_probe_one_driver(struct rte_pci_driver *dr,
> >  			 struct rte_pci_device *dev)
> >  {
> >  	int ret;
> > +	unsigned int socket_id;
> >  	bool already_probed;
> >  	struct rte_pci_addr *loc;
> >  
> > @@ -194,7 +195,8 @@ rte_pci_probe_one_driver(struct rte_pci_driver *dr,
> >  		if (rte_socket_count() > 1)
> >  			RTE_LOG(INFO, EAL, "Device %s is not NUMA-aware, defaulting socket to 0\n",
> >  					dev->name);
> 
> One more comment (sorry, I should have done it before you send the mail):
> We should move this log below, and use the socket_id instead of 0.
> 
> > -		dev->device.numa_node = 0;
> > +		socket_id = rte_lcore_to_socket_id(rte_get_next_lcore(-1, 0, 0));
> > +		dev->device.numa_node = socket_id;

After some offline discussions with David, some additional comments:

- a similar change may be needed in other bus drivers

- instead of setting the numa node to an existing socket, it can make
  more sense to keep its value to unknown (-1). This would however be a
  behavior change for pci bus, which returns 0 since 2015 for unknown
  cases. See:
    81f8d2317df2 ("eal/linux: fix socket value for undetermined numa node")
    8a04cb612589 ("pci: set default numa node for broken systems")

I'll tend to be in favor of using -1. Any other opinion?
Should we announce a behavior change in this case?

> >  	}
> >  
> >  	already_probed = rte_dev_is_probed(&dev->device);
> > -- 
> > 2.30.2
> >