Re: [dpdk-dev] [PATCH 02/20] librte_ether: add fields from rte_pci_driver to rte_eth_dev_data

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

On Wed, Sep 30, 2015 at 09:14:48AM -0400, Neil Horman wrote:
> On Wed, Sep 30, 2015 at 10:56:04AM +0100, Bruce Richardson wrote:
> > On Tue, Sep 29, 2015 at 03:08:12PM -0400, Neil Horman wrote:
> > > On Mon, Sep 28, 2015 at 02:03:20PM +0100, Bernard Iremonger wrote:
> > > > add dev_flags to rte_eth_dev_data, add macros for dev_flags.
> > > > add kdrv to rte_eth_dev_data.
> > > > add numa_node to rte_eth_dev_data.
> > > > add drv_name to rte_eth_dev_data.
> > > > use dev_type to distinguish between vdev's and pdev's.
> > > > remove pci_dev branches.
> > > > 
> > > > Signed-off-by: Bernard Iremonger <bernard.iremonger@intel.com>
> > > > ---
> > > >  lib/librte_ether/rte_ethdev.c | 53 ++++++++++++++++++++++++-------------------
> > > >  lib/librte_ether/rte_ethdev.h | 15 ++++++++++++
> > > >  2 files changed, 45 insertions(+), 23 deletions(-)
> > > > 
> > <snip>
> > > > +++ b/lib/librte_ether/rte_ethdev.h
> > > > @@ -1635,8 +1635,23 @@ struct rte_eth_dev_data {
> > > >  		all_multicast : 1, /**< RX all multicast mode ON(1) / OFF(0). */
> > > >  		dev_started : 1,   /**< Device state: STARTED(1) / STOPPED(0). */
> > > >  		lro         : 1;   /**< RX LRO is ON(1) / OFF(0) */
> > > > +	uint32_t dev_flags; /**< Flags controlling handling of device. */
> > > > +	enum rte_kernel_driver kdrv;	/**< Kernel driver passthrough */
> > > Why add this here? The ennumerated driver types are all variants on PCI bus
> > > types.  Not sure why the ethernet interface needs to know this info
> > > 
> > > > +	int numa_node;
> > > Ditto, this seems like information that is only relevant if the device is on a
> > > physical bus (i.e. virual devices are likely to not have a numa node)
> > >
> > Actually, I disagree. For some virtual devices they will have a numa node. For
> > ring or other virtual PMDs the numa node will be the node on which the ring /
> > mempool etc. memory is allocated on, and can be of relevance.
> > 
> > /Bruce
> > 
> 
> I think its fairly clear that some devices (including virtual ones) have some
> relevant relation to a numa_node (There are even some that have no numa_node,
> for which a -1 value makes some sense).  That said, there are just as many that
> don't have a relevant numa_node.
> 
> 1) There are some drivers for which numa_node make no sense (regardless of
> value):
>  * af_packet - The numa node is at best determined at run time by the interface
> the socket is bound to
> 
>  * pcap - same as af_packet
> 
>  * bonding - multiple interfaces mean multiple numa_nodes, any value set here is
> just as likely to be wrong as right
> 
>  * mpipe - no real large memory area to associate with a numa node
> 
>  * virtio - uses iopl for communication, and cannot know its numa_node
> 
>  * vmxnet3 - same concept as virtio
> 
>  * xenvirt - same as vmxnet3
> 
> I think its better that you store numa locality information in a pmd's private
> bus data, and export it to applications via a device method.  that provides the
> flexibility to tell the application that there is no numa locality for a device
> (by not implementing the method), without having to expose an unset data field
> to the application.
> 
> Neil
> 

Sure, that could work.
However, is it really worthwhile asking drivers to implement a new ethdev API
function, rather than just having them set the numa node field correctly in the
init function?

/Bruce