Re: [dpdk-dev] [PATCH v4 1/4] hash: add kv hash library

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

> Hi Vladimir,
> 
> > --- /dev/null
> > +++ b/lib/librte_hash/k32v64_hash.c
> > @@ -0,0 +1,277 @@
> > +/* SPDX-License-Identifier: BSD-3-Clause
> > + * Copyright(c) 2020 Intel Corporation
> > + */
> > +
> > +#include <string.h>
> > +
> > +#include <rte_errno.h>
> > +#include <rte_malloc.h>
> > +#include <rte_memory.h>
> > +
> > +#include "k32v64_hash.h"
> > +
> > +static inline int
> > +k32v64_hash_lookup(struct k32v64_hash_table *table, uint32_t key,
> > +	uint32_t hash, uint64_t *value)
> > +{
> > +	return __k32v64_hash_lookup(table, key, hash, value, __kv_cmp_keys);
> > +}
> > +
> > +static int
> > +k32v64_hash_bulk_lookup(struct rte_kv_hash_table *ht, void *keys_p,
> > +	uint32_t *hashes, void *values_p, unsigned int n)
> > +{
> > +	struct k32v64_hash_table *table = (struct k32v64_hash_table *)ht;
> > +	uint32_t *keys = keys_p;
> > +	uint64_t *values = values_p;
> > +	int ret, cnt = 0;
> > +	unsigned int i;
> > +
> > +	if (unlikely((table == NULL) || (keys == NULL) || (hashes == NULL) ||
> > +			(values == NULL)))
> > +		return -EINVAL;


As a nit - this formal parameter checking better to do in public function
(rte_kv_hash_bulk_lookup) before de-refencing table and calling actual lookup().  
Same story for modify() - formal parameter checking can be done at the top of public function.
BTW, why to unite add/delete into modify(), if internally you have 2 different functions
(for add/delete) anyway?

> > +
> > +	for (i = 0; i < n; i++) {
> > +		ret = k32v64_hash_lookup(table, keys[i], hashes[i],
> > +			&values[i]);
> > +		if (ret == 0)
> > +			cnt++;
> > +	}
> > +	return cnt;
> > +}
> > +
> > +#ifdef CC_AVX512VL_SUPPORT
> > +int
> > +k32v64_hash_bulk_lookup_avx512vl(struct rte_kv_hash_table *ht,
> > +	void *keys_p, uint32_t *hashes, void *values_p, unsigned int n);
> > +#endif
> > +
> > +static rte_kv_hash_bulk_lookup_t
> > +get_lookup_bulk_fn(void)
> > +{
> > +#ifdef CC_AVX512VL_SUPPORT
> > +	if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_AVX512VL))
> > +		return k32v64_hash_bulk_lookup_avx512vl;
> > +#endif
> > +	return k32v64_hash_bulk_lookup;
> > +}
> > +
> > +static int
> > +k32v64_hash_add(struct k32v64_hash_table *table, uint32_t key,
> > +	uint32_t hash, uint64_t value, uint64_t *old_value, int *found)
> > +{
> > +	uint32_t bucket;
> > +	int i, idx, ret;
> > +	uint8_t msk;
> > +	struct k32v64_ext_ent *tmp, *ent, *prev = NULL;
> > +
> > +	if (table == NULL)
> > +		return -EINVAL;
> > +
> > +	bucket = hash & table->bucket_msk;
> > +	/* Search key in table. Update value if exists */
> > +	for (i = 0; i < K32V64_KEYS_PER_BUCKET; i++) {
> > +		if ((key == table->t[bucket].key[i]) &&
> > +				(table->t[bucket].key_mask & (1 << i))) {
> > +			*old_value = table->t[bucket].val[i];
> > +			*found = 1;
> > +			__atomic_fetch_add(&table->t[bucket].cnt, 1,
> > +				__ATOMIC_ACQUIRE);

After another thought - atomic add is probably an overkill here.
Something like:
void update_start(struct k32v64_hash_bucket *bkt)
{
	bkt->cnt++;
        __atomic_thread_fence(__ATOMIC_ACQ_REL);
}

void update_finish(struct k32v64_hash_bucket *bkt)
{
	__atomic_thread_fence(__ATOMIC_ACQ_REL);
	bkt->cnt++;
}

I think should be sufficient here.

> > +			table->t[bucket].val[i] = value;
> > +			__atomic_fetch_add(&table->t[bucket].cnt, 1,
> > +				__ATOMIC_RELEASE);
> > +			return 0;
> > +		}
> > +	}
> > +
> > +	if (!SLIST_EMPTY(&table->t[bucket].head)) {
> > +		SLIST_FOREACH(ent, &table->t[bucket].head, next) {
> > +			if (ent->key == key) {
> > +				*old_value = ent->val;
> > +				*found = 1;
> > +				__atomic_fetch_add(&table->t[bucket].cnt, 1,
> > +					__ATOMIC_ACQUIRE);
> > +				ent->val = value;
> > +				__atomic_fetch_add(&table->t[bucket].cnt, 1,
> > +					__ATOMIC_RELEASE);
> > +				return 0;
> > +			}
> > +		}
> > +	}
> > +
> > +	msk = ~table->t[bucket].key_mask & VALID_KEY_MSK;
> > +	if (msk) {
> > +		idx = __builtin_ctz(msk);
> > +		table->t[bucket].key[idx] = key;
> > +		table->t[bucket].val[idx] = value;
> > +		__atomic_or_fetch(&table->t[bucket].key_mask, 1 << idx,
> > +			__ATOMIC_RELEASE);
> 
> I think this case also has to guarded with table->t[bucket].cnt updates.
> 
> > +		table->nb_ent++;
> > +		*found = 0;
> > +		return 0;
> > +	}
> > +
> > +	ret = rte_mempool_get(table->ext_ent_pool, (void **)&ent);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	SLIST_NEXT(ent, next) = NULL;
> > +	ent->key = key;
> > +	ent->val = value;
> > +	rte_smp_wmb();
> 
> __atomic_thread_fence(__ATOMIC_RELEASE);
> ?
> 
> > +	SLIST_FOREACH(tmp, &table->t[bucket].head, next)
> > +		prev = tmp;
> > +
> > +	if (prev == NULL)
> > +		SLIST_INSERT_HEAD(&table->t[bucket].head, ent, next);
> > +	else
> > +		SLIST_INSERT_AFTER(prev, ent, next);
> > +
> > +	table->nb_ent++;
> > +	table->nb_ext_ent++;
> > +	*found = 0;
> > +	return 0;
> > +}
> > +
> > +static int
> > +k32v64_hash_delete(struct k32v64_hash_table *table, uint32_t key,
> > +	uint32_t hash, uint64_t *old_value)
> > +{
> > +	uint32_t bucket;
> > +	int i;
> > +	struct k32v64_ext_ent *ent;
> > +
> > +	if (table == NULL)
> > +		return -EINVAL;
> > +
> > +	bucket = hash & table->bucket_msk;
> > +
> > +	for (i = 0; i < K32V64_KEYS_PER_BUCKET; i++) {
> > +		if ((key == table->t[bucket].key[i]) &&
> > +				(table->t[bucket].key_mask & (1 << i))) {
> > +			*old_value = table->t[bucket].val[i];
> > +			ent = SLIST_FIRST(&table->t[bucket].head);
> > +			if (ent) {
> > +				__atomic_fetch_add(&table->t[bucket].cnt, 1,
> > +					__ATOMIC_ACQUIRE);
> > +				table->t[bucket].key[i] = ent->key;
> > +				table->t[bucket].val[i] = ent->val;
> > +				SLIST_REMOVE_HEAD(&table->t[bucket].head, next);
> > +				__atomic_fetch_add(&table->t[bucket].cnt, 1,
> > +					__ATOMIC_RELEASE);
> > +				table->nb_ext_ent--;
> > +			} else
> > +				__atomic_and_fetch(&table->t[bucket].key_mask,
> > +					~(1 << i), __ATOMIC_RELEASE);
> 
> Same thought as above - safer to guard this mask update with cnt update.
> 
> > +			if (ent)
> > +				rte_mempool_put(table->ext_ent_pool, ent);
> 
> Can't this 'if(ent)' be merged with previous 'if (ent) {...}' above?
> 
> > +			table->nb_ent--;
> > +			return 0;
> > +		}
> > +	}
> > +
> > +	SLIST_FOREACH(ent, &table->t[bucket].head, next)
> > +		if (ent->key == key)
> > +			break;
> > +
> > +	if (ent == NULL)
> > +		return -ENOENT;
> > +
> > +	*old_value = ent->val;
> > +
> > +	__atomic_fetch_add(&table->t[bucket].cnt, 1, __ATOMIC_ACQUIRE);
> > +	SLIST_REMOVE(&table->t[bucket].head, ent, k32v64_ext_ent, next);
> > +	__atomic_fetch_add(&table->t[bucket].cnt, 1, __ATOMIC_RELEASE);
> > +	rte_mempool_put(table->ext_ent_pool, ent);
> > +
> > +	table->nb_ext_ent--;
> > +	table->nb_ent--;
> > +
> > +	return 0;
> > +}
> > +