Re: [PATCH v6] enhance NUMA affinity heuristic

[Thomas Monjalon <thomas@monjalon.net>]

25/04/2023 07:16, Kaisen You:
> Trying to allocate memory on the first detected numa node,it has less
> chance to find some memory actually available rather than on the main
> lcore numa node (especially when the DPDK application is started only
> on one numa node).

You didn't change the explanations here as discussed previously.

> 
> Fixes: 8b0a1b8cb481 ("eal: stop using pthread for lcores and control threads")
> Fixes: 770d41bf3309 ("malloc: fix allocation with unknown socket ID")
> Cc: stable@dpdk.org
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> Signed-off-by: Kaisen You <kaisenx.you@intel.com>
> 
> ---
> Changes since v5:
> - Add comments to the code,
> 
> Changes since v4:
> - mod the patch title,
> 
> Changes since v3:
> - add the assignment of socket_id in thread initialization,
> 
> Changes since v2:
> - add uncommitted local change and fix compilation,
> 
> Changes since v1:
> - accomodate for configurations with main lcore running on multiples
>   physical cores belonging to different numa,
> ---
>  lib/eal/common/eal_common_thread.c | 4 ++++
>  lib/eal/common/malloc_heap.c       | 6 ++++++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/lib/eal/common/eal_common_thread.c b/lib/eal/common/eal_common_thread.c
> index 079a385630..d65bfe251b 100644
> --- a/lib/eal/common/eal_common_thread.c
> +++ b/lib/eal/common/eal_common_thread.c
> @@ -252,6 +252,10 @@ static int ctrl_thread_init(void *arg)
>  	struct rte_thread_ctrl_params *params = arg;
>  
>  	__rte_thread_init(rte_lcore_id(), cpuset);
> +	/* set the value of the per-core variable _socket_id.
> +	 * Convenient for threads to find memory.
> +	 */

That's an useless comment.
We want to know WHY you are setting to SOCKET_ID_ANY.

> +	RTE_PER_LCORE(_socket_id) = SOCKET_ID_ANY;
>  	params->ret = rte_thread_set_affinity_by_id(rte_thread_self(), cpuset);
>  	if (params->ret != 0) {
>  		__atomic_store_n(&params->ctrl_thread_status,
> diff --git a/lib/eal/common/malloc_heap.c b/lib/eal/common/malloc_heap.c
> index d25bdc98f9..a624f08cf7 100644
> --- a/lib/eal/common/malloc_heap.c
> +++ b/lib/eal/common/malloc_heap.c
> @@ -716,6 +716,12 @@ malloc_get_numa_socket(void)
>  		if (conf->socket_mem[socket_id] != 0)
>  			return socket_id;
>  	}
> +	/* Trying to allocate memory on the main lcore numa node.
> +	 * especially when the DPDK application is started only on one numa node.
> +	 */
> +	socket_id = rte_lcore_to_socket_id(rte_get_main_lcore());
> +	if (socket_id != (unsigned int)SOCKET_ID_ANY)
> +		return socket_id;

You should explain why we could reach this point, i.e. SOCKET_ID_ANY.

>  
>  	return rte_socket_id_by_idx(0);
>  }