On Thu, 24 May 2018, Linus Torvalds wrote:
This doesn't seem to be taking 'param->min_size' into account.
It was in that rounded_hashtable_size() does, however, after more thought I think we can do better by taking it much more into account.
I'm not sure that matters, but right now, if you have nelem_hint set and a min_size, the min_size is honored (if you have just min_size it's already ignored because the rhashtable always starts with HASH_DEFAULT_SIZE). So I could imagine that somebody uses it to guarantee something. The docs say that "min_size" is the minimum size for *shrinking* not for initializing, so I guess it's debatable. Also, wouldn't it make sense to make this all be a while loop? Or are you just depending on the knowledge that HASH_DEFAULT_SIZE / 2 is already guaranteed to be so small that there's no point? A comment to that effect would be good, perhaps.
Yes, this is why I didn't loop. With the default size of 64 buckets, we allocate 640 + 128 = 768 bytes for the tbl and the lock array, respectively. By halving this, upon retrying, I was relying on it being to "small to fail". However, after how about the resize being based on HASH_MIN_SIZE instead of HASH_DEFAULT_SIZE? That way the initial table would be a _lot_ smaller and aid the allocator that much more; which is why we're here in the first place. Any performance costs of collisions would be completely unimportant in this scenario. Considering that some users set p.min_size to be rather large-ish (up to 1024 buckets afaict), we'd need the following: size = min(ht->p.min_size, HASH_MIN_SIZE); Which takes into account the min_size = max(ht->p.min_size, HASH_MIN_SIZE) which came before, thus p.min_size == 0 is already taken into account. Thanks, Davidlohr -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
