Re: [PATCH v2 2/3] eal/freebsd: Avoid claiming memseg holes

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 8/14/2025 11:32 PM, Jake Freeland wrote:
> When need_hole is false, memseg searches will only be done for a single
> element. If the search starts at beginning of the list, an element that
> was previously reserved as a hole may be wrongly claimed.
> 
> To avoid this, begin the search following the last used entry. This way,
> we ignore all pre-existing holes.
> 
> Signed-off-by: Jake Freeland <jfree@FreeBSD.org>
> ---
>   lib/eal/freebsd/eal_memory.c | 19 +++++++++++++++++--
>   1 file changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/eal/freebsd/eal_memory.c b/lib/eal/freebsd/eal_memory.c
> index be3bde2cb9..b159e9ef4e 100644
> --- a/lib/eal/freebsd/eal_memory.c
> +++ b/lib/eal/freebsd/eal_memory.c
> @@ -143,6 +143,7 @@ rte_eal_hugepage_init(void)
>   
>   			for (msl_idx = 0; msl_idx < RTE_MAX_MEMSEG_LISTS;
>   					msl_idx++) {
> +				int start_idx, num_elems;
>   				bool empty, need_hole;
>   				msl = &mcfg->memsegs[msl_idx];
>   				arr = &msl->memseg_arr;
> @@ -157,10 +158,24 @@ rte_eal_hugepage_init(void)
>   				 * adjacent to current one.
>   				 */
>   				need_hole = !empty && !is_adjacent;
> +				if (need_hole) {
> +					start_idx = 0;
> +					/* we need 1, plus hole */
> +					num_elems = 2;
> +				} else {
> +					/* begin our search after the last used
> +					 * element in the list, skipping over
> +					 * any previously placed holes
> +					 */
> +					start_idx = rte_fbarray_find_prev_n_used(
> +							arr, arr->len - 1, 1) + 1;
> +					if (start_idx < 0)
> +						start_idx = 0;

Actually, I think this check is largely redundant, because even if 
find_prev_n_used returns -1 (empty array case), we immediately +1 the 
result, so it's always 0 at a minimum.

> +					num_elems = 1;
> +				}
>   
> -				/* we need 1, plus hole if not adjacent */
>   				ms_idx = rte_fbarray_find_next_n_free(arr,
> -						0, 1 + (need_hole ? 1 : 0));
> +						start_idx, num_elems);
>   
>   				/* memseg list is full? */
>   				if (ms_idx < 0)


-- 
Thanks,
Anatoly