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items.c
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/* -*- Mode: C; tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
* arcus-memcached - Arcus memory cache server
* Copyright 2010-2014 NAVER Corp.
*
* 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.
*/
#include "config.h"
#include <fcntl.h>
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <assert.h>
#include <inttypes.h>
#include <sys/time.h> /* gettimeofday() */
#include "default_engine.h"
/* item unlink cause */
enum item_unlink_cause {
ITEM_UNLINK_NORMAL = 1, /* unlink by normal request */
ITEM_UNLINK_EVICT, /* unlink by eviction */
ITEM_UNLINK_INVALID, /* unlink by invalidation such like expiration/flush */
ITEM_UNLINK_REPLACE, /* unlink by replacement of set/replace command,
* simple kv type only
*/
ITEM_UNLINK_ABORT, /* unlink by abortion of creating a collection
* collection type only
*/
ITEM_UNLINK_EMPTY, /* unlink by empty collection
* collection type only
*/
ITEM_UNLINK_STALE /* unlink by staleness */
};
/* element delete cause */
enum elem_delete_cause {
ELEM_DELETE_NORMAL = 1, /* delete by normal request */
ELEM_DELETE_COLL, /* delete by collection deletion */
ELEM_DELETE_TRIM /* delete by overflow trim */
};
/* Forward Declarations */
static void item_link_q(struct default_engine *engine, hash_item *it);
static void item_unlink_q(struct default_engine *engine, hash_item *it);
static hash_item *do_item_alloc(struct default_engine *engine,
const void *key, const size_t nkey,
const int flags, const rel_time_t exptime,
const int nbytes, const void *cookie);
static hash_item *do_item_get(struct default_engine *engine,
const char *key, const size_t nkey,
bool LRU_reposition);
static ENGINE_ERROR_CODE do_item_link(struct default_engine *engine, hash_item *it);
static void do_item_unlink(struct default_engine *engine, hash_item *it,
enum item_unlink_cause cause);
static void do_item_release(struct default_engine *engine, hash_item *it);
static void do_item_update(struct default_engine *engine, hash_item *it);
static void do_item_lru_reposition(struct default_engine *engine, hash_item *it);
static ENGINE_ERROR_CODE do_item_replace(struct default_engine *engine,
hash_item *it, hash_item *new_it);
static void do_item_free(struct default_engine *engine, hash_item *it);
static void push_coll_del_queue(struct default_engine *engine, hash_item *it);
static void do_coll_all_elem_delete(struct default_engine *engine, hash_item *it);
extern int genhash_string_hash(const void* p, size_t nkey);
/*
* We only reposition items in the LRU queue if they haven't been repositioned
* in this many seconds. That saves us from churning on frequently-accessed
* items.
*/
#define ITEM_UPDATE_INTERVAL 60
/* LRU id of small memory items */
#define LRU_CLSID_FOR_SMALL 0
/* item type checking */
#define IS_LIST_ITEM(it) (((it)->iflag & ITEM_IFLAG_LIST) != 0)
#define IS_SET_ITEM(it) (((it)->iflag & ITEM_IFLAG_SET) != 0)
#define IS_BTREE_ITEM(it) (((it)->iflag & ITEM_IFLAG_BTREE) != 0)
#define IS_COLL_ITEM(it) (((it)->iflag & ITEM_IFLAG_COLL) != 0)
/* btree item status */
#define BTREE_ITEM_STATUS_USED 2
#define BTREE_ITEM_STATUS_UNLINK 1
#define BTREE_ITEM_STATUS_FREE 0
/* btree scan direction */
#define BTREE_DIRECTION_PREV 2
#define BTREE_DIRECTION_NEXT 1
#define BTREE_DIRECTION_NONE 0
/* bkey type */
#define BKEY_TYPE_UNKNOWN 0
#define BKEY_TYPE_UINT64 1
#define BKEY_TYPE_BINARY 2
/* binary bkey min & max length */
#define BKEY_MIN_BINARY_LENG 1
#define BKEY_MAX_BINARY_LENG MAX_BKEY_LENG
/* uint64 bkey min & max value */
#define BTREE_UINT64_MIN_BKEY 0
#define BTREE_UINT64_MAX_BKEY (uint64_t)((int64_t)-1) /* need check */
/* btree element item or btree node item */
#define BTREE_GET_ELEM_ITEM(node, indx) ((btree_elem_item *)((node)->item[indx]))
#define BTREE_GET_NODE_ITEM(node, indx) ((btree_indx_node *)((node)->item[indx]))
/* get bkey real size */
#define BTREE_REAL_NBKEY(nbkey) ((nbkey)==0 ? sizeof(uint64_t) : (nbkey))
/* overflow type */
#define OVFL_TYPE_NONE 0
#define OVFL_TYPE_COUNT 1
#define OVFL_TYPE_RANGE 2
/* bkey range type */
#define BKEY_RANGE_TYPE_SIN 1 /* single bkey */
#define BKEY_RANGE_TYPE_ASC 2 /* ascending bkey range */
#define BKEY_RANGE_TYPE_DSC 3 /* descending bkey range */
/* special address for representing unlinked status */
#define ADDR_MEANS_UNLINKED 1
/* collection meta flag */
#define COLL_META_FLAG_READABLE 2
#define COLL_META_FLAG_STICKY 4
#define COLL_META_FLAG_TRIMMED 8
/** How long an object can reasonably be assumed to be locked before
* harvesting it on a low memory condition. */
#define TAIL_REPAIR_TIME (3 * 3600)
/* btree position debugging */
static bool btree_position_debug = false;
/* min & max bkey constants */
static uint64_t btree_uint64_min_bkey = BTREE_UINT64_MIN_BKEY;
static uint64_t btree_uint64_max_bkey = BTREE_UINT64_MAX_BKEY;
static unsigned char btree_binary_min_bkey[BKEY_MIN_BINARY_LENG] = { 0x00 };
static unsigned char btree_binary_max_bkey[BKEY_MAX_BINARY_LENG] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
/* maximum collection size */
static int32_t coll_size_limit = 100000;
static int32_t max_list_size = 50000;
static int32_t max_set_size = 50000;
static int32_t max_btree_size = 50000;
/* default collection size */
static int32_t default_list_size = 4000;
static int32_t default_set_size = 4000;
static int32_t default_btree_size = 4000;
static EXTENSION_LOGGER_DESCRIPTOR *logger;
/*
* Static functions
*/
/* warning: don't use these macros with a function, as it evals its arg twice */
static inline size_t ITEM_ntotal(struct default_engine *engine, const hash_item *item)
{
size_t ret;
if (IS_COLL_ITEM(item)) {
ret = sizeof(*item) + META_OFFSET_IN_ITEM(item->nkey, item->nbytes);
if (IS_LIST_ITEM(item)) ret += sizeof(list_meta_info);
else if (IS_SET_ITEM(item)) ret += sizeof(set_meta_info);
else /* BTREE_ITEM */ ret += sizeof(btree_meta_info);
} else {
ret = sizeof(*item) + item->nkey + item->nbytes;
}
if (engine->config.use_cas) {
ret += sizeof(uint64_t);
}
return ret;
}
static inline size_t ITEM_stotal(struct default_engine *engine, const hash_item *item)
{
size_t ntotal = ITEM_ntotal(engine, item);
size_t stotal = slabs_space_size(engine, ntotal);
if (IS_COLL_ITEM(item)) {
coll_meta_info *info = (coll_meta_info *)item_get_meta(item);
stotal += info->stotal;
}
return stotal;
}
/* Get the next CAS id for a new item. */
static uint64_t get_cas_id(void)
{
static uint64_t cas_id = 0;
return ++cas_id;
}
/* Enable this for reference-count debugging. */
#if 0
# define DEBUG_REFCNT(it,op) \
fprintf(stderr, "item %x refcnt(%c) %d %c%c%c\n", \
it, op, it->refcount, \
(it->it_flags & ITEM_LINKED) ? 'L' : ' ', \
(it->it_flags & ITEM_SLABBED) ? 'S' : ' ')
#else
# define DEBUG_REFCNT(it,op) while(0)
#endif
static void increase_collection_space(struct default_engine *engine, ENGINE_ITEM_TYPE item_type,
coll_meta_info *info, const size_t inc_space)
{
info->stotal += inc_space;
/* Currently, stats.lock is useless since global cache lock is held. */
//pthread_mutex_lock(&engine->stats.lock);
#ifdef ENABLE_STICKY_ITEM
if ((info->mflags & COLL_META_FLAG_STICKY) != 0)
engine->stats.sticky_bytes += inc_space;
#endif
assoc_prefix_update_size(info->prefix, item_type, inc_space, true);
engine->stats.curr_bytes += inc_space;
//pthread_mutex_unlock(&engine->stats.lock);
}
static void decrease_collection_space(struct default_engine *engine, ENGINE_ITEM_TYPE item_type,
coll_meta_info *info, const size_t dec_space)
{
assert(info->stotal >= dec_space);
info->stotal -= dec_space;
/* Currently, stats.lock is useless since global cache lock is held. */
//pthread_mutex_lock(&engine->stats.lock);
#ifdef ENABLE_STICKY_ITEM
if ((info->mflags & COLL_META_FLAG_STICKY) != 0)
engine->stats.sticky_bytes -= dec_space;
#endif
assoc_prefix_update_size(info->prefix, item_type, dec_space, false);
engine->stats.curr_bytes -= dec_space;
//pthread_mutex_unlock(&engine->stats.lock);
}
static bool do_item_isvalid(struct default_engine *engine, hash_item *it, rel_time_t current_time)
{
/* check if it's expired */
#ifdef ENABLE_STICKY_ITEM
/* The sticky item has an exptime((rel_tiem_t)(-1)) larger than current_item.
* So, it cannot be expired.
**/
#endif
if (it->exptime != 0 && it->exptime <= current_time) {
return false; /* expired */
}
/* check flushed items as well as expired items */
if (engine->config.oldest_live != 0) {
if (engine->config.oldest_live <= current_time && it->time <= engine->config.oldest_live)
return false; /* flushed by flush_all */
}
/* check if prefix is valid */
if (assoc_prefix_isvalid(engine, it) == false) {
return false;
}
return true; /* Yes, it's a valid item */
}
static hash_item *do_item_reclaim(struct default_engine *engine, hash_item *it,
const size_t ntotal, const unsigned int clsid,
const unsigned int lruid)
{
/* increment # of reclaimed */
pthread_mutex_lock(&engine->stats.lock);
engine->stats.reclaimed++;
pthread_mutex_unlock(&engine->stats.lock);
engine->items.itemstats[lruid].reclaimed++;
/* it->refcount == 0 */
#ifdef USE_SINGLE_LRU_LIST
#else
if (lruid != LRU_CLSID_FOR_SMALL) {
it->refcount = 1;
slabs_adjust_mem_requested(engine, it->slabs_clsid, ITEM_ntotal(engine,it), ntotal);
do_item_unlink(engine, it, ITEM_UNLINK_INVALID);
/* Initialize the item block: */
it->slabs_clsid = 0;
it->refcount = 0;
return it;
}
/* collection item or small-sized kv item */
#endif
if (IS_COLL_ITEM(it))
do_coll_all_elem_delete(engine, it);
do_item_unlink(engine, it, ITEM_UNLINK_INVALID);
/* allocate from slab allocator */
it = slabs_alloc(engine, ntotal, clsid);
return it;
}
static void do_item_evict(struct default_engine *engine, hash_item *it,
const unsigned int lruid,
rel_time_t current_time, const void *cookie)
{
/* increment # of evicted */
engine->items.itemstats[lruid].evicted++;
engine->items.itemstats[lruid].evicted_time = current_time - it->time;
if (it->exptime != 0) {
engine->items.itemstats[lruid].evicted_nonzero++;
}
pthread_mutex_lock(&engine->stats.lock);
engine->stats.evictions++;
pthread_mutex_unlock(&engine->stats.lock);
if (cookie != NULL) {
engine->server.stat->evicting(cookie, item_get_key(it), it->nkey);
}
/* unlink the item */
if (IS_COLL_ITEM(it))
do_coll_all_elem_delete(engine, it);
do_item_unlink(engine, it, ITEM_UNLINK_EVICT);
}
static void do_item_repair(struct default_engine *engine, hash_item *it,
const unsigned int lruid)
{
/* increment # of repaired */
engine->items.itemstats[lruid].tailrepairs++;
it->refcount = 0;
/* unlink the item */
if (IS_COLL_ITEM(it))
do_coll_all_elem_delete(engine, it);
do_item_unlink(engine, it, ITEM_UNLINK_EVICT);
}
static void do_item_invalidate(struct default_engine *engine, hash_item *it,
const unsigned int lruid, bool immediate)
{
/* increment # of reclaimed */
pthread_mutex_lock(&engine->stats.lock);
engine->stats.reclaimed++;
pthread_mutex_unlock(&engine->stats.lock);
engine->items.itemstats[lruid].reclaimed++;
/* it->refcount == 0 */
if (immediate) {
if (IS_COLL_ITEM(it)) {
do_coll_all_elem_delete(engine, it);
}
}
do_item_unlink(engine, it, ITEM_UNLINK_INVALID);
}
static void *do_item_alloc_internal(struct default_engine *engine,
const size_t ntotal, const unsigned int clsid,
const void *cookie)
{
hash_item *it = NULL;
/* do a quick check if we have any expired items in the tail.. */
int tries;
hash_item *search;
hash_item *previt = NULL;
rel_time_t current_time = engine->server.core->get_current_time();
#ifdef USE_SINGLE_LRU_LIST
unsigned int id = 1;
unsigned int clsid_based_on_ntotal = 1;
if ((it = slabs_alloc(engine, ntotal, clsid_based_on_ntotal)) != NULL) {
it->slabs_clsid = 0;
return (void*)it;
}
#else
unsigned int id;
unsigned int clsid_based_on_ntotal;
if (clsid == LRU_CLSID_FOR_SMALL) {
clsid_based_on_ntotal = slabs_clsid(engine, ntotal);
id = clsid;
} else {
clsid_based_on_ntotal = clsid;
if (ntotal <= MAX_SM_VALUE_SIZE) {
id = LRU_CLSID_FOR_SMALL;
} else {
id = clsid;
}
}
#endif
int space_shortage_level = slabs_space_shortage_level();
if (space_shortage_level > 0 &&
id == LRU_CLSID_FOR_SMALL && engine->config.evict_to_free != 0)
{
tries = space_shortage_level;
search = engine->items.tails[id];
while (search != NULL) {
if (search->refcount == 0 && search->nkey > 0) {
previt = search->prev;
if (do_item_isvalid(engine, search, current_time) == false) {
do_item_invalidate(engine, search, id, true);
} else {
do_item_evict(engine, search, id, current_time, cookie);
}
search = previt;
} else { /* search->nkey == 0: scrub cursor item */
search = search->prev; /* ignore it */
}
if ((--tries) == 0) break;
}
}
#ifdef ENABLE_STICKY_ITEM
/* reclaim the flushed sticky items */
if (engine->items.sticky_curMK[id] != NULL) {
tries = 20;
while (engine->items.sticky_curMK[id] != NULL) {
search = engine->items.sticky_curMK[id];
engine->items.sticky_curMK[id] = search->prev;
if (search->nkey > 0 && search->refcount == 0 &&
do_item_isvalid(engine, search, current_time) == false) {
it = do_item_reclaim(engine, search, ntotal, clsid_based_on_ntotal, id);
if (it != NULL) break; /* allocated */
}
if ((--tries) == 0) break;
}
if (it != NULL) {
/* try one more invalidation */
search = engine->items.sticky_curMK[id];
if (search != NULL && search->nkey > 0 && search->refcount == 0 &&
do_item_isvalid(engine, search, current_time) == false) {
do_item_invalidate(engine, search, id, false);
}
it->slabs_clsid = 0;
return (void*)it;
}
}
#endif
if (engine->items.curMK[id] != NULL) {
assert(engine->items.lowMK[id] != NULL);
/* step 1) reclaim items from lowMK position */
tries = 20;
search = engine->items.lowMK[id];
while (search != NULL && search != engine->items.curMK[id]) {
if (search->nkey > 0 && search->refcount == 0 &&
do_item_isvalid(engine, search, current_time) == false) {
previt = search->prev;
it = do_item_reclaim(engine, search, ntotal, clsid_based_on_ntotal, id);
if (it != NULL) break; /* allocated */
search = previt;
} else {
if (search->exptime == 0 && search == engine->items.lowMK[id]) {
/* The scrub cursor item also corresponds to this case. */
engine->items.lowMK[id] = search->prev; /* move lowMK position upward */
}
search = search->prev;
}
if ((--tries) == 0) break;
}
if (it != NULL) {
/* try one more invalidation */
if (previt != NULL && previt->nkey > 0 && previt->refcount == 0 &&
do_item_isvalid(engine, previt, current_time) == false) {
do_item_invalidate(engine, previt, id, false);
}
it->slabs_clsid = 0;
return (void *)it;
}
/* step 2) reclaim items from curMK position */
tries += 20;
while (engine->items.curMK[id] != NULL) {
search = engine->items.curMK[id];
engine->items.curMK[id] = search->prev;
if (search->nkey > 0 && search->refcount == 0 &&
do_item_isvalid(engine, search, current_time) == false) {
it = do_item_reclaim(engine, search, ntotal, clsid_based_on_ntotal, id);
if (it != NULL) break; /* allocated */
}
if ((--tries) == 0) break;
}
if (engine->items.curMK[id] == NULL) {
engine->items.curMK[id] = engine->items.lowMK[id];
}
if (it != NULL) {
/* try one more invalidation */
search = engine->items.curMK[id];
if (search != NULL && search->nkey > 0 && search->refcount == 0 &&
do_item_isvalid(engine, search, current_time) == false) {
do_item_invalidate(engine, search, id, false);
}
it->slabs_clsid = 0;
return (void *)it;
}
}
it = slabs_alloc(engine, ntotal, clsid_based_on_ntotal);
if (it == NULL) {
/*
** Could not find an expired item at the tail, and memory allocation
** failed. Try to evict some items!
*/
/* If requested to not push old items out of cache when memory runs out,
* we're out of luck at this point...
*/
if (engine->config.evict_to_free == 0) {
engine->items.itemstats[clsid_based_on_ntotal].outofmemory++;
return NULL;
}
/*
* try to get one off the right LRU
* don't necessariuly unlink the tail because it may be locked: refcount>0
* search up from tail an item with refcount==0 and unlink it; give up after 50
* tries
*/
tries = 200;
search = engine->items.tails[id];
while (search != NULL) {
if (search->refcount == 0 && search->nkey > 0) {
previt = search->prev;
if (do_item_isvalid(engine, search, current_time) == false) {
it = do_item_reclaim(engine, search, ntotal, clsid_based_on_ntotal, id);
} else {
do_item_evict(engine, search, id, current_time, cookie);
it = slabs_alloc(engine, ntotal, clsid_based_on_ntotal);
}
if (it != NULL) break; /* allocated */
search = previt;
} else { /* search->nkey == 0: scrub cursor item */
search = search->prev; /* ignore it */
}
if ((--tries) == 0) break;
}
}
if (it == NULL) {
engine->items.itemstats[id].outofmemory++;
/* Last ditch effort. There is a very rare bug which causes
* refcount leaks. We've fixed most of them, but it still happens,
* and it may happen in the future.
* We can reasonably assume no item can stay locked for more than
* three hours, so if we find one in the tail which is that old,
* free it anyway.
*/
if (id <= POWER_LARGEST) {
tries = 50;
search = engine->items.tails[id];
while (search != NULL) {
if (search->nkey > 0 && search->refcount != 0 &&
search->time + TAIL_REPAIR_TIME < current_time) {
previt = search->prev;
do_item_repair(engine, search, id);
it = slabs_alloc(engine, ntotal, clsid_based_on_ntotal);
if (it != NULL) break; /* allocated */
search = previt;
} else {
search = search->prev;
}
if ((--tries) == 0) break;
}
}
}
if (it != NULL) {
it->slabs_clsid = 0;
}
return (void *)it;
}
/*@null@*/
static hash_item *do_item_alloc(struct default_engine *engine,
const void *key, const size_t nkey,
const int flags, const rel_time_t exptime,
const int nbytes, const void *cookie)
{
hash_item *it = NULL;
size_t ntotal = sizeof(hash_item) + nkey + nbytes;
if (engine->config.use_cas) {
ntotal += sizeof(uint64_t);
}
unsigned int id = slabs_clsid(engine, ntotal);
if (id == 0) {
return NULL;
}
#ifdef ENABLE_STICKY_ITEM
/* sticky memory limit check */
if (exptime == (rel_time_t)(-1)) { /* sticky item */
if (engine->stats.sticky_bytes >= engine->config.sticky_limit)
return NULL;
}
#endif
it = do_item_alloc_internal(engine, ntotal, id, cookie);
if (it == NULL) {
return NULL;
}
assert(it->slabs_clsid == 0);
it->slabs_clsid = id;
assert(it != engine->items.heads[it->slabs_clsid]);
it->next = it->prev = it->h_next = 0;
it->refcount = 1; /* the caller will have a reference */
DEBUG_REFCNT(it, '*');
it->iflag = engine->config.use_cas ? ITEM_WITH_CAS : 0;
it->nkey = nkey;
it->nbytes = nbytes;
it->flags = flags;
memcpy((void*)item_get_key(it), key, nkey);
it->exptime = exptime;
it->nprefix = 0;
return it;
}
static void do_item_free(struct default_engine *engine, hash_item *it)
{
size_t ntotal = ITEM_ntotal(engine, it);
unsigned int clsid;
assert((it->iflag & ITEM_LINKED) == 0);
assert(it != engine->items.heads[it->slabs_clsid]);
assert(it != engine->items.tails[it->slabs_clsid]);
assert(it->refcount == 0);
if (IS_COLL_ITEM(it)) {
coll_meta_info *info = (coll_meta_info *)item_get_meta(it);
if (info->ccnt > 0) { /* NOT empty collection (list or set) */
push_coll_del_queue(engine, it);
return;
}
}
/* so slab size changer can tell later if item is already free or not */
clsid = it->slabs_clsid;
it->slabs_clsid = 0;
it->iflag |= ITEM_SLABBED;
DEBUG_REFCNT(it, 'F');
slabs_free(engine, it, ntotal, clsid);
}
static void item_link_q(struct default_engine *engine, hash_item *it)
{
hash_item **head, **tail;
assert(it->slabs_clsid <= POWER_LARGEST);
assert((it->iflag & ITEM_SLABBED) == 0);
#ifdef USE_SINGLE_LRU_LIST
int clsid = 1;
#else
int clsid = it->slabs_clsid;
if (IS_COLL_ITEM(it) || ITEM_ntotal(engine, it) <= MAX_SM_VALUE_SIZE) {
clsid = LRU_CLSID_FOR_SMALL;
}
#endif
#ifdef ENABLE_STICKY_ITEM
if (it->exptime == (rel_time_t)(-1)) {
head = &engine->items.sticky_heads[clsid];
tail = &engine->items.sticky_tails[clsid];
engine->items.sticky_sizes[clsid]++;
} else {
#endif
head = &engine->items.heads[clsid];
tail = &engine->items.tails[clsid];
engine->items.sizes[clsid]++;
if (it->exptime > 0) { /* expirable item */
if (engine->items.lowMK[clsid] == NULL) {
/* set lowMK and curMK pointer in LRU */
engine->items.lowMK[clsid] = it;
engine->items.curMK[clsid] = it;
}
}
#ifdef ENABLE_STICKY_ITEM
}
#endif
assert(it != *head);
assert((*head && *tail) || (*head == 0 && *tail == 0));
it->prev = 0;
it->next = *head;
if (it->next) it->next->prev = it;
*head = it;
if (*tail == 0) *tail = it;
return;
}
static void item_unlink_q(struct default_engine *engine, hash_item *it)
{
hash_item **head, **tail;
assert(it->slabs_clsid <= POWER_LARGEST);
#ifdef USE_SINGLE_LRU_LIST
int clsid = 1;
#else
int clsid = it->slabs_clsid;
if (IS_COLL_ITEM(it) || ITEM_ntotal(engine, it) <= MAX_SM_VALUE_SIZE) {
clsid = LRU_CLSID_FOR_SMALL;
}
#endif
#ifdef ENABLE_STICKY_ITEM
if (it->exptime == (rel_time_t)(-1)) {
head = &engine->items.sticky_heads[clsid];
tail = &engine->items.sticky_tails[clsid];
engine->items.sticky_sizes[clsid]--;
/* move curMK, srcub pointer in LRU */
if (engine->items.sticky_curMK[clsid] == it)
engine->items.sticky_curMK[clsid] = it->prev;
if (engine->items.sticky_scrub[clsid] == it)
engine->items.sticky_scrub[clsid] = it->next; /* move forward */
} else {
#endif
head = &engine->items.heads[clsid];
tail = &engine->items.tails[clsid];
engine->items.sizes[clsid]--;
/* move lowMK, curMK, srcub pointer in LRU */
if (engine->items.lowMK[clsid] == it)
engine->items.lowMK[clsid] = it->prev;
if (engine->items.curMK[clsid] == it) {
engine->items.curMK[clsid] = it->prev;
if (engine->items.curMK[clsid] == NULL)
engine->items.curMK[clsid] = engine->items.lowMK[clsid];
}
if (engine->items.scrub[clsid] == it)
engine->items.scrub[clsid] = it->next; /* move forward */
#ifdef ENABLE_STICKY_ITEM
}
#endif
if (*head == it) {
assert(it->prev == 0);
*head = it->next;
}
if (*tail == it) {
assert(it->next == 0);
*tail = it->prev;
}
assert(it->next != it);
assert(it->prev != it);
if (it->next) it->next->prev = it->prev;
if (it->prev) it->prev->next = it->next;
return;
}
static ENGINE_ERROR_CODE do_item_link(struct default_engine *engine, hash_item *it)
{
MEMCACHED_ITEM_LINK(item_get_key(it), it->nkey, it->nbytes);
assert((it->iflag & (ITEM_LINKED|ITEM_SLABBED)) == 0);
assert(it->nbytes < (1024 * 1024)); /* 1MB max size */
size_t stotal = ITEM_stotal(engine, it);
/* link given item to prefix */
prefix_t *pt;
ENGINE_ERROR_CODE ret = assoc_prefix_link(engine, it, stotal, &pt);
if (ret != ENGINE_SUCCESS) {
return ret;
}
if (IS_COLL_ITEM(it)) {
coll_meta_info *info = (coll_meta_info *)item_get_meta(it);
info->prefix = (void*)pt;
assert(info->stotal == 0); /* Only empty collection can be linked */
}
it->iflag |= ITEM_LINKED;
it->time = engine->server.core->get_current_time();
assoc_insert(engine, engine->server.core->hash(item_get_key(it), it->nkey, 0), it);
pthread_mutex_lock(&engine->stats.lock);
#ifdef ENABLE_STICKY_ITEM
if (it->exptime == (rel_time_t)(-1)) { /* sticky item */
engine->stats.sticky_bytes += stotal;
engine->stats.sticky_items += 1;
}
#endif
engine->stats.curr_bytes += stotal;
engine->stats.curr_items += 1;
engine->stats.total_items += 1;
pthread_mutex_unlock(&engine->stats.lock);
/* Allocate a new CAS ID on link. */
item_set_cas(it, get_cas_id());
item_link_q(engine, it);
return ENGINE_SUCCESS;
}
static void do_item_unlink(struct default_engine *engine, hash_item *it,
enum item_unlink_cause cause)
{
/* cause: item unlink cause will be used, later
*/
MEMCACHED_ITEM_UNLINK(item_get_key(it), it->nkey, it->nbytes);
if ((it->iflag & ITEM_LINKED) != 0) {
it->iflag &= ~ITEM_LINKED;
size_t stotal = ITEM_stotal(engine, it);
pthread_mutex_lock(&engine->stats.lock);
#ifdef ENABLE_STICKY_ITEM
if (it->exptime == (rel_time_t)(-1)) { /* sticky item */
engine->stats.sticky_bytes -= stotal;
engine->stats.sticky_items -= 1;
}
#endif
engine->stats.curr_bytes -= stotal;
engine->stats.curr_items -= 1;
pthread_mutex_unlock(&engine->stats.lock);
/* unlink given item from prefix */
assoc_prefix_unlink(engine, it, stotal);
if (IS_COLL_ITEM(it)) {
coll_meta_info *info = (coll_meta_info *)item_get_meta(it);
info->prefix = NULL;
info->stotal = 0; /* Don't need to decrease space statistics any more */
}
assoc_delete(engine, engine->server.core->hash(item_get_key(it), it->nkey, 0),
item_get_key(it), it->nkey);
item_unlink_q(engine, it);
if (it->refcount == 0) {
do_item_free(engine, it);
}
}
}
static void do_item_release(struct default_engine *engine, hash_item *it)
{
MEMCACHED_ITEM_REMOVE(item_get_key(it), it->nkey, it->nbytes);
if (it->refcount != 0) {
it->refcount--;
DEBUG_REFCNT(it, '-');
}
if (it->refcount == 0 && (it->iflag & ITEM_LINKED) == 0) {
do_item_free(engine, it);
}
}
static void do_item_update(struct default_engine *engine, hash_item *it)
{
rel_time_t current_time = engine->server.core->get_current_time();
MEMCACHED_ITEM_UPDATE(item_get_key(it), it->nkey, it->nbytes);
if (it->time < current_time - ITEM_UPDATE_INTERVAL) {
assert((it->iflag & ITEM_SLABBED) == 0);
if ((it->iflag & ITEM_LINKED) != 0) {
item_unlink_q(engine, it);
it->time = current_time;
item_link_q(engine, it);
}
}
}
static void do_item_lru_reposition(struct default_engine *engine, hash_item *it)
{
assert((it->iflag & ITEM_SLABBED) == 0);
if ((it->iflag & ITEM_LINKED) != 0) {
item_unlink_q(engine, it);
it->time = engine->server.core->get_current_time();
item_link_q(engine, it);
}
}
static ENGINE_ERROR_CODE do_item_replace(struct default_engine *engine,
hash_item *it, hash_item *new_it)
{
MEMCACHED_ITEM_REPLACE(item_get_key(it), it->nkey, it->nbytes,
item_get_key(new_it), new_it->nkey, new_it->nbytes);
assert((it->iflag & ITEM_SLABBED) == 0);
do_item_unlink(engine, it, ITEM_UNLINK_REPLACE);
ENGINE_ERROR_CODE ret = do_item_link(engine, new_it);
assert(ret == ENGINE_SUCCESS);
return ret;
}
/*@null@*/
static char *do_item_cachedump(struct default_engine *engine, const unsigned int slabs_clsid,
const unsigned int limit, const bool forward, const bool sticky,
unsigned int *bytes)
{
unsigned int memlimit = 256 * 1024; /* 256KB max response size */
char *buffer;
unsigned int bufcurr = 0;
hash_item *it;
unsigned int len;
unsigned int shown = 0;
char key_temp[256]; /* KEY_MAX_LENGTH + 1 */
buffer = malloc((size_t)memlimit);
if (buffer == 0) return NULL;
if (sticky) {
it = (forward ? engine->items.sticky_heads[slabs_clsid]
: engine->items.sticky_tails[slabs_clsid]);
} else {
it = (forward ? engine->items.heads[slabs_clsid]
: engine->items.tails[slabs_clsid]);
}
while (it != NULL && (limit == 0 || shown < limit)) {
/* Copy the key since it may not be null-terminated in the struct */
strncpy(key_temp, item_get_key(it), it->nkey);
key_temp[it->nkey] = 0x00; /* terminate */
if (bufcurr + it->nkey + 100 > memlimit) break;
len = sprintf(buffer + bufcurr, "ITEM %s [acctime=%u, exptime=%d]\r\n",
key_temp, it->time, (int32_t)it->exptime);
bufcurr += len;
shown++;
it = (forward ? it->next : it->prev);
}
len = sprintf(buffer + bufcurr, "END [curtime=%u]\r\n",
engine->server.core->get_current_time());
bufcurr += len;
*bytes = bufcurr;
return buffer;
}
static void do_item_stats(struct default_engine *engine, ADD_STAT add_stats, const void *c)
{
const char *prefix = "items";
for (int i = 0; i <= POWER_LARGEST; i++)
{
if (engine->items.tails[i] == NULL && engine->items.sticky_tails[i] == NULL)
continue;
add_statistics(c, add_stats, prefix, i, "number", "%u",
engine->items.sizes[i]+engine->items.sticky_sizes[i]);
#ifdef ENABLE_STICKY_ITEM
add_statistics(c, add_stats, prefix, i, "sticky", "%u",
engine->items.sticky_sizes[i]);
#endif
add_statistics(c, add_stats, prefix, i, "age", "%u",
(engine->items.tails[i] != NULL ? engine->items.tails[i]->time : 0));
add_statistics(c, add_stats, prefix, i, "evicted",
"%u", engine->items.itemstats[i].evicted);
add_statistics(c, add_stats, prefix, i, "evicted_nonzero",
"%u", engine->items.itemstats[i].evicted_nonzero);
add_statistics(c, add_stats, prefix, i, "evicted_time",
"%u", engine->items.itemstats[i].evicted_time);
add_statistics(c, add_stats, prefix, i, "outofmemory",
"%u", engine->items.itemstats[i].outofmemory);
add_statistics(c, add_stats, prefix, i, "tailrepairs",
"%u", engine->items.itemstats[i].tailrepairs);;
add_statistics(c, add_stats, prefix, i, "reclaimed",
"%u", engine->items.itemstats[i].reclaimed);;
}
}
/** dumps out a list of objects of each size, with granularity of 32 bytes */
/*@null@*/
static void do_item_stats_sizes(struct default_engine *engine, ADD_STAT add_stats, const void *c)
{
/* "stats sizes" has too much overhead to execute,
* since it traverses all of the items cached in memory.
* So, we disabled "stats sizes" execution.
*/
return;
#if 0 // disabled below code.
/* max 1MB object, divided into 32 bytes size buckets */
const int num_buckets = 32768;
unsigned int *histogram = calloc(num_buckets, sizeof(int));
if (histogram != NULL) {
int i;
/* build the histogram */
for (i = 0; i <= POWER_LARGEST; i++)
{
hash_item *iter = engine->items.heads[i];
while (iter) {
int ntotal = ITEM_stotal(engine, iter);
int bucket = ntotal / 32;
if ((ntotal % 32) != 0) bucket++;
if (bucket < num_buckets) histogram[bucket]++;
iter = iter->next;
}
#ifdef ENABLE_STICKY_ITEM
iter = engine->items.sticky_heads[i];
while (iter) {
int ntotal = ITEM_stotal(engine, iter);
int bucket = ntotal / 32;
if ((ntotal % 32) != 0) bucket++;
if (bucket < num_buckets) histogram[bucket]++;