[question] I guess up to the size limit of eBPF Maps.

[Bobcat-yang]

Hello,
I would like to know what is the size limit of eBPF Maps in Linux? How much data can I store when using it?
I did not find the answer in the documentation, so I asked this question here. Hope to get your reply.

Thank you.

[yonghong-song]

There is no documentation. You can see the source code, e.g.,
https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/kernel/bpf/hashtab.c

if ((u64)attr->key_size + attr->value_size >= KMALLOC_MAX_SIZE -
	   sizeof(struct htab_elem))
		/* if key_size + value_size is bigger, the user space won't be
		 * able to access the elements via bpf syscall. This check
		 * also makes sure that the elem_size doesn't overflow and it's
		 * kmalloc-able later in htab_map_update_elem()
		 */
		return -E2BIG;

or

	/* hash table size must be power of 2; roundup_pow_of_two() can overflow
	 * into UB on 32-bit arches, so check that first
	 */
	err = -E2BIG;
	if (htab->map.max_entries > 1UL << 31)
		goto free_htab;

Similarly you can check other files for other map types.