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/*
* Copyright (c) 2012 Cisco and/or its affiliates.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* vppinfra already includes tons of different hash tables.
* MagLev flow table is a bit different. It has to be very efficient
* for both writing and reading operations. But it does not need to
* be 100% reliable (write can fail). It also needs to recycle
* old entries in a lazy way.
*
* This hash table is the most trivial hash table you can do.
* Fixed total size, fixed bucket size.
* Advantage is that it could be very efficient (maybe).
*
*/
#ifndef LB_PLUGIN_LB_LBHASH_H_
#define LB_PLUGIN_LB_LBHASH_H_
#include <vnet/vnet.h>
#include <vppinfra/lb_hash_hash.h>
#if defined (__SSE4_2__)
#include <immintrin.h>
#endif
/*
* @brief Number of entries per bucket.
*/
#define LBHASH_ENTRY_PER_BUCKET 4
#define LB_HASH_DO_NOT_USE_SSE_BUCKETS 0
/*
* @brief One bucket contains 4 entries.
* Each bucket takes one 64B cache line in memory.
*/
typedef struct {
CLIB_CACHE_LINE_ALIGN_MARK (cacheline0);
u32 hash[LBHASH_ENTRY_PER_BUCKET];
u32 timeout[LBHASH_ENTRY_PER_BUCKET];
u32 vip[LBHASH_ENTRY_PER_BUCKET];
u32 value[LBHASH_ENTRY_PER_BUCKET];
} lb_hash_bucket_t;
typedef struct {
u32 buckets_mask;
u32 timeout;
lb_hash_bucket_t buckets[];
} lb_hash_t;
#define lb_hash_nbuckets(h) (((h)->buckets_mask) + 1)
#define lb_hash_size(h) ((h)->buckets_mask + LBHASH_ENTRY_PER_BUCKET)
#define lb_hash_foreach_bucket(h, bucket) \
for (bucket = (h)->buckets; \
bucket < (h)->buckets + lb_hash_nbuckets(h); \
bucket++)
#define lb_hash_foreach_entry(h, bucket, i) \
lb_hash_foreach_bucket(h, bucket) \
for (i = 0; i < LBHASH_ENTRY_PER_BUCKET; i++)
#define lb_hash_foreach_valid_entry(h, bucket, i, now) \
lb_hash_foreach_entry(h, bucket, i) \
if (!clib_u32_loop_gt((now), bucket->timeout[i]))
static_always_inline
lb_hash_t *lb_hash_alloc(u32 buckets, u32 timeout)
{
if (!is_pow2(buckets))
return NULL;
// Allocate 1 more bucket for prefetch
u32 size = ((uword)&((lb_hash_t *)(0))->buckets[0]) +
sizeof(lb_hash_bucket_t) * (buckets + 1);
u8 *mem = 0;
lb_hash_t *h;
vec_validate_aligned (mem, size - 1, CLIB_CACHE_LINE_BYTES);
h = (lb_hash_t *)mem;
h->buckets_mask = (buckets - 1);
h->timeout = timeout;
return h;
}
static_always_inline
void lb_hash_free(lb_hash_t *h)
{
u8 *mem = (u8 *)h;
vec_free(mem);
}
static_always_inline
void lb_hash_prefetch_bucket(lb_hash_t *ht, u32 hash)
{
lb_hash_bucket_t *bucket = &ht->buckets[hash & ht->buckets_mask];
CLIB_PREFETCH(bucket, sizeof(*bucket), READ);
}
static_always_inline
void lb_hash_get(lb_hash_t *ht, u32 hash, u32 vip, u32 time_now,
u32 *available_index, u32 *found_value)
{
lb_hash_bucket_t *bucket = &ht->buckets[hash & ht->buckets_mask];
*found_value = 0;
*available_index = ~0;
#if __SSE4_2__ && LB_HASH_DO_NOT_USE_SSE_BUCKETS == 0
u32 bitmask, found_index;
__m128i mask;
// mask[*] = timeout[*] > now
mask = _mm_cmpgt_epi32(_mm_loadu_si128 ((__m128i *) bucket->timeout),
_mm_set1_epi32 (time_now));
// bitmask[*] = now <= timeout[*/4]
bitmask = (~_mm_movemask_epi8(mask)) & 0xffff;
// Get first index with now <= timeout[*], if any.
*available_index = (bitmask)?__builtin_ctz(bitmask)/4:*available_index;
// mask[*] = (timeout[*] > now) && (hash[*] == hash)
mask = _mm_and_si128(mask,
_mm_cmpeq_epi32(
_mm_loadu_si128 ((__m128i *) bucket->hash),
_mm_set1_epi32 (hash)));
// Load the array of vip values
// mask[*] = (timeout[*] > now) && (hash[*] == hash) && (vip[*] == vip)
mask = _mm_and_si128(mask,
_mm_cmpeq_epi32(
_mm_loadu_si128 ((__m128i *) bucket->vip),
_mm_set1_epi32 (vip)));
// mask[*] = (timeout[*x4] > now) && (hash[*x4] == hash) && (vip[*x4] == vip)
bitmask = _mm_movemask_epi8(mask);
// Get first index, if any
found_index = (bitmask)?__builtin_ctzll(bitmask)/4:0;
ASSERT(found_index < 4);
*found_value = (bitmask)?bucket->value[found_index]:*found_value;
bucket->timeout[found_index] =
(bitmask)?time_now + ht->timeout:bucket->timeout[found_index];
#else
u32 i;
for (i = 0; i < LBHASH_ENTRY_PER_BUCKET; i++) {
u8 cmp = (bucket->hash[i] == hash && bucket->vip[i] == vip);
u8 timeouted = clib_u32_loop_gt(time_now, bucket->timeout[i]);
*found_value = (cmp || timeouted)?*found_value:bucket->value[i];
bucket->timeout[i] = (cmp || timeouted)?time_now + ht->timeout:bucket->timeout[i];
*available_index = (timeouted && (*available_index == ~0))?i:*available_index;
if (!cmp)
return;
}
#endif
}
static_always_inline
u32 lb_hash_available_value(lb_hash_t *h, u32 hash, u32 available_index)
{
return h->buckets[hash & h->buckets_mask].value[available_index];
}
static_always_inline
void lb_hash_put(lb_hash_t *h, u32 hash, u32 value, u32 vip,
u32 available_index, u32 time_now)
{
lb_hash_bucket_t *bucket = &h->buckets[hash & h->buckets_mask];
bucket->hash[available_index] = hash;
bucket->value[available_index] = value;
bucket->timeout[available_index] = time_now + h->timeout;
bucket->vip[available_index] = vip;
}
static_always_inline
u32 lb_hash_elts(lb_hash_t *h, u32 time_now)
{
u32 tot = 0;
lb_hash_bucket_t *bucket;
u32 i;
lb_hash_foreach_valid_entry(h, bucket, i, time_now) {
tot++;
}
return tot;
}
#endif /* LB_PLUGIN_LB_LBHASH_H_ */
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