Re: [dpdk-dev] [PATCH 24/25] net/ena: fix direct access to shared memory config

["Michał Krawczyk" <mk@semihalf.com>]

On 29.05.2019 18:31, Anatoly Burakov wrote:
> The ENA driver calculates a ring's NUMA node affinity by directly
> accessing the memzone list. Fix it to do it through the public
> API's instead.
> 
> Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
> ---
>   drivers/net/ena/ena_ethdev.c | 18 +++---------------
>   1 file changed, 3 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/net/ena/ena_ethdev.c b/drivers/net/ena/ena_ethdev.c
> index b6651fc0f..e745e9e92 100644
> --- a/drivers/net/ena/ena_ethdev.c
> +++ b/drivers/net/ena/ena_ethdev.c
> @@ -274,20 +274,6 @@ static const struct eth_dev_ops ena_dev_ops = {
>   
>   #define NUMA_NO_NODE	SOCKET_ID_ANY
>   
> -static inline int ena_cpu_to_node(int cpu)
> -{
> -	struct rte_config *config = rte_eal_get_configuration();
> -	struct rte_fbarray *arr = &config->mem_config->memzones;
> -	const struct rte_memzone *mz;
> -
> -	if (unlikely(cpu >= RTE_MAX_MEMZONE))
> -		return NUMA_NO_NODE;
> -
> -	mz = rte_fbarray_get(arr, cpu);
> -
> -	return mz->socket_id;
> -}
> -
>   static inline void ena_rx_mbuf_prepare(struct rte_mbuf *mbuf,
>   				       struct ena_com_rx_ctx *ena_rx_ctx)
>   {
> @@ -1099,6 +1085,7 @@ static int ena_create_io_queue(struct ena_ring *ring)
>   {
>   	struct ena_adapter *adapter;
>   	struct ena_com_dev *ena_dev;
> +	struct rte_memseg_list *msl;
>   	struct ena_com_create_io_ctx ctx =
>   		/* policy set to _HOST just to satisfy icc compiler */
>   		{ ENA_ADMIN_PLACEMENT_POLICY_HOST,
> @@ -1126,7 +1113,8 @@ static int ena_create_io_queue(struct ena_ring *ring)
>   	}
>   	ctx.qid = ena_qid;
>   	ctx.msix_vector = -1; /* interrupts not used */
> -	ctx.numa_node = ena_cpu_to_node(ring->id);
> +	msl = rte_mem_virt2memseg_list(ring);
> +	ctx.numa_node = msl->socket_id;
>   
>   	rc = ena_com_create_io_queue(ena_dev, &ctx);
>   	if (rc) {
> 

Hi Anatoly,

I'm not sure why the previous maintainers implemented this that way, I 
can only guess. I think that they were assuming, that each queue will be 
assigned to the lcore which is equal to ring id. They probably also 
misunderstood how the memzones are working and they thought that each 
lcore is having assigned only one memzone which is being mapped 1 to 1.

They wanted to prevent cross NUMA data acces, when the CPU is operating 
in the different NUMA zone and the IO queues memory resides in the 
other. I think that above solution won't prevent that neither, as you 
are using ring address, which is being allocated together with
struct ena_adapter (it is just an array), so it will probably reside in 
the single numa zone.

I'm currently thinking on solution that could help us to determine on 
which numa zone the queue descriptors will be allocated and on which the 
lcore assigned to the queue will be working, but have no any ideas for 
now :)

Anyway, your fix won't break anything, as the previous solution wasn't 
working as it was supposed to work, so before I will fix that, we can 
keep that patch to prevent direct usage of the memzone.

Thanks,
Michal