Re: [PATCH 2/3] eal: implement functions for get/set thread affinity

[Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>]

2022-04-01 06:29 (UTC-0700), Tyler Retzlaff:
> Implement functions for getting/setting thread affinity.
> Threads can be pinned to specific cores by setting their
> affinity attribute.
> 
> Signed-off-by: Narcisa Vasile <navasile@microsoft.com>
> Signed-off-by: Tyler Retzlaff <roretzla@linux.microsoft.com>

Acked-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>

Please see some small comments below.

> ---
>  lib/eal/include/rte_thread.h     |  45 ++++++++++
>  lib/eal/unix/rte_thread.c        |  16 ++++
>  lib/eal/version.map              |   4 +
>  lib/eal/windows/eal_lcore.c      | 173 +++++++++++++++++++++++++++++----------
>  lib/eal/windows/eal_windows.h    |  10 +++
>  lib/eal/windows/include/rte_os.h |   2 +
>  lib/eal/windows/rte_thread.c     | 131 ++++++++++++++++++++++++++++-
>  7 files changed, 336 insertions(+), 45 deletions(-)
> 
> diff --git a/lib/eal/include/rte_thread.h b/lib/eal/include/rte_thread.h
> index 8be8ed8..4eb113f 100644
> --- a/lib/eal/include/rte_thread.h
> +++ b/lib/eal/include/rte_thread.h
> @@ -2,6 +2,8 @@
>   * Copyright(c) 2021 Mellanox Technologies, Ltd
>   */
>  
> +#include <stdint.h>
> +
>  #include <rte_os.h>
>  #include <rte_compat.h>
>  
> @@ -21,6 +23,13 @@
>  #endif
>  
>  /**
> + * Thread id descriptor.
> + */
> +typedef struct rte_thread_tag {
> +	uintptr_t opaque_id; /**< thread identifier */
> +} rte_thread_t;
> +
> +/**
>   * TLS key type, an opaque pointer.
>   */
>  typedef struct eal_tls_key *rte_thread_key;
> @@ -28,6 +37,42 @@
>  #ifdef RTE_HAS_CPUSET
>  
>  /**

Missing a common part for experimental functions:

 * @warning
 * @b EXPERIMENTAL: this API may change without prior notice.

> + * Set the affinity of thread 'thread_id' to the cpu set
> + * specified by 'cpuset'.
> + *
> + * @param thread_id
> + *    Id of the thread for which to set the affinity.
> + *
> + * @param cpuset
> + *   Pointer to CPU affinity to set.
> + *
> + * @return
> + *   On success, return 0.
> + *   On failure, return a positive errno-style error number.
> + */
> +__rte_experimental
> +int rte_thread_set_affinity_by_id(rte_thread_t thread_id,
> +		const rte_cpuset_t *cpuset);
> +
> +/**

Same here.

> + * Get the affinity of thread 'thread_id' and store it
> + * in 'cpuset'.
> + *
> + * @param thread_id
> + *    Id of the thread for which to get the affinity.
> + *
> + * @param cpuset
> + *   Pointer for storing the affinity value.
> + *
> + * @return
> + *   On success, return 0.
> + *   On failure, return a positive errno-style error number.
> + */
> +__rte_experimental
> +int rte_thread_get_affinity_by_id(rte_thread_t thread_id,
> +		rte_cpuset_t *cpuset);
> +
> +/**
>   * Set core affinity of the current thread.
>   * Support both EAL and non-EAL thread and update TLS.
>   *

[...]

> +static int
> +eal_query_group_affinity(void)
> +{
> +	SYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX *infos = NULL;
> +	unsigned int *cpu_count = &cpu_map.cpu_count;
> +	DWORD infos_size = 0;
> +	int ret = 0;
> +	USHORT group_count;
> +	KAFFINITY affinity;
> +	USHORT group_no;
> +	unsigned int i;
> +
> +	if (!GetLogicalProcessorInformationEx(RelationGroup, NULL,
> +			&infos_size)) {
> +		DWORD error = GetLastError();
> +		if (error != ERROR_INSUFFICIENT_BUFFER) {
> +			log_early("Cannot get group information size, "
> +				"error %lu\n", error);

Please don't break string constants for easy search.

> +			rte_errno = EINVAL;
> +			ret = -1;
> +			goto cleanup;
> +		}
> +	}
[...]

> +static bool
> +eal_create_lcore_map(const SYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX *info)
> +{
> +	const unsigned int node_id = info->NumaNode.NodeNumber;
> +	const GROUP_AFFINITY *cores = &info->NumaNode.GroupMask;
> +	struct lcore_map *lcore;
> +	unsigned int socket_id;
> +	unsigned int i;
> +
> +	/* NUMA node may be reported multiple times if it includes
> +	 * cores from different processor groups, e. g. 80 cores
> +	 * of a physical processor comprise one NUMA node, but two
> +	 * processor groups, because group size is limited by 32/64.
> +	 */
> +	for (socket_id = 0; socket_id < cpu_map.socket_count; socket_id++) {
> +		if (cpu_map.sockets[socket_id].node_id == node_id)
> +			break;
> +	}

Nit: multi-line comments should start with a line containing just "/*",
and {} are no needed here.

[...]
> +static int
> +rte_convert_cpuset_to_affinity(const rte_cpuset_t *cpuset,
> +		PGROUP_AFFINITY affinity)
> +{
> +	int ret = 0;
> +	PGROUP_AFFINITY cpu_affinity = NULL;
> +	unsigned int cpu_idx;
> +
> +	memset(affinity, 0, sizeof(GROUP_AFFINITY));
> +	affinity->Group = (USHORT)-1;
> +
> +	/* Check that all cpus of the set belong to the same processor group and
> +	 * accumulate thread affinity to be applied.
> +	 */
> +	for (cpu_idx = 0; cpu_idx < CPU_SETSIZE; cpu_idx++) {
> +		if (!CPU_ISSET(cpu_idx, cpuset))
> +			continue;
> +
> +		cpu_affinity = eal_get_cpu_affinity(cpu_idx);
> +
> +		if (affinity->Group == (USHORT)-1) {
> +			affinity->Group = cpu_affinity->Group;
> +		} else if (affinity->Group != cpu_affinity->Group) {
> +			ret = EINVAL;

Should it be ENOTSUP, because we don't support this case?
This limitation is also worth documenting in the commit log.

> +			goto cleanup;
> +		}
> +
> +		affinity->Mask |= cpu_affinity->Mask;
> +	}
> +
> +	if (affinity->Mask == 0) {
> +		ret = EINVAL;
> +		goto cleanup;
> +	}
> +
> +cleanup:
> +	return ret;
> +}
[...]