cds_lfht_new() clarification - init vs min

["Ondřej Surý via lttng-dev" <lttng-dev@lists.lttng.org>]

Hi,

as the answer to this might be useful to more people, I am asking here:

The cds_lfht_new documentation specifies 3 sizes.

 * cds_lfht_new - allocate a hash table.
 * @init_size: number of buckets to allocate initially. Must be power of two.
 * @min_nr_alloc_buckets: the minimum number of allocated buckets.
 *                        (must be power of two)
 * @max_nr_buckets: the maximum number of hash table buckets allowed.
 *                  (must be power of two, 0 is accepted, means
 *                  "infinite")

The max number of buckets is obvious, but the interaction between init
and min is confusing.

If I am reading the code right, then init_size < min_nr_alloc_buckets have no
effect, the buckets table will be at least 1 << min_nr_alloc_buckets.

But what happens if init_size > min_nr_alloc_buckets? It feels like it will work
as expected if you pre-populate the table, but if you use it "normally", e.g. there
could be single add / del, the table will shrink immediately.

Do I understand the code correctly?

Ondrej
--
Ondřej Surý (He/Him)
ondrej@sury.org