/*
* Unlinks an item from the LRU and hashtable.
*/
void item_unlink(item *item) {
uint32_t hv;
hv = hash(ITEM_key(item), item->nkey, 0);
item_lock(hv);
do_item_unlink(item, hv);
item_unlock(hv);
}
/*
* Decrements the reference count on an item and adds it to the freelist if
* needed.
*/
void item_remove(item *item) {
uint32_t hv;
hv = hash(ITEM_key(item), item->nkey);
item_lock(hv);
do_item_remove(item);
item_unlock(hv);
}
item *item_touch(const char *key, size_t nkey, uint32_t exptime) {
item *it;
uint32_t hv;
hv = hash(key, nkey, 0);
item_lock(hv);
it = do_item_touch(key, nkey, exptime, hv);
item_unlock(hv);
return it;
}
/*
* Returns an item if it hasn't been marked as expired,
* lazy-expiring as needed.
*/
item *item_get(const char *key, const size_t nkey, conn *c, const bool do_update) {
item *it;
uint32_t hv;
hv = hash(key, nkey);
item_lock(hv);
it = do_item_get(key, nkey, hv, c, do_update);
item_unlock(hv);
return it;
}
/*
* Returns an item if it hasn't been marked as expired,
* lazy-expiring as needed.
*/
item *item_get(const char *key, const size_t nkey) {
item *it;
uint32_t hv;
hv = hash(key, nkey);
item_lock(hv);
it = do_item_get(key, nkey, hv);
item_unlock(hv);
return it;
}
/*
* Links an item into the LRU and hashtable.
*/
int item_link(item *item) {
int ret;
uint32_t hv;
hv = hash(ITEM_key(item), item->nkey, 0);
item_lock(hv);
ret = do_item_link(item, hv);
item_unlock(hv);
return ret;
}
/*
* Stores an item in the cache (high level, obeys set/add/replace semantics)
*/
enum store_item_type store_item(item *item, int comm, conn* c) {
enum store_item_type ret;
uint32_t hv;
hv = hash(ITEM_key(item), item->nkey);
item_lock(hv);
ret = do_store_item(item, comm, c, hv);
item_unlock(hv);
return ret;
}
/*
* Stores an item in the cache (high level, obeys set/add/replace semantics)
*/
enum store_item_type store_item(item *item, int comm, conn* c) { //注意该函数外层在该函数执行完后一般会调用一次item_remove
enum store_item_type ret;
uint32_t hv;
hv = hash(ITEM_key(item), item->nkey);
item_lock(hv);
ret = do_store_item(item, comm, c, hv);
item_unlock(hv);
return ret;
}
/*
* Does arithmetic on a numeric item value.
*/
enum delta_result_type add_delta(conn *c, const char *key,
const size_t nkey, int incr,
const int64_t delta, char *buf,
uint64_t *cas) {
enum delta_result_type ret;
uint32_t hv;
hv = hash(key, nkey);
item_lock(hv);
ret = do_add_delta(c, key, nkey, incr, delta, buf, cas, hv);
item_unlock(hv);
return ret;
}
/*
* Stores an item in the cache (high level, obeys set/add/replace semantics)
* 在缓存中存储一个数据项
*/
enum store_item_type store_item(item *item, int comm, conn* c) {
enum store_item_type ret;
uint32_t hv;
// 先做一次哈希计算
hv = hash(ITEM_key(item), item->nkey, 0);
item_lock(hv);
// 正真存储数据的方法 do_store_item()
ret = do_store_item(item, comm, c, hv);
item_unlock(hv);
return ret;
}
static void storage_compact_readback(void *storage, logger *l,
bool drop_unread, char *readback_buf,
uint32_t page_id, uint64_t page_version, uint64_t read_size) {
uint64_t offset = 0;
unsigned int rescues = 0;
unsigned int lost = 0;
unsigned int skipped = 0;
while (offset < read_size) {
item *hdr_it = NULL;
item_hdr *hdr = NULL;
item *it = (item *)(readback_buf+offset);
unsigned int ntotal;
// probably zeroed out junk at the end of the wbuf
if (it->nkey == 0) {
break;
}
ntotal = ITEM_ntotal(it);
uint32_t hv = (uint32_t)it->time;
item_lock(hv);
// We don't have a conn and don't need to do most of do_item_get
hdr_it = assoc_find(ITEM_key(it), it->nkey, hv);
if (hdr_it != NULL) {
bool do_write = false;
refcount_incr(hdr_it);
// Check validity but don't bother removing it.
if ((hdr_it->it_flags & ITEM_HDR) && !item_is_flushed(hdr_it) &&
(hdr_it->exptime == 0 || hdr_it->exptime > current_time)) {
hdr = (item_hdr *)ITEM_data(hdr_it);
if (hdr->page_id == page_id && hdr->page_version == page_version) {
// Item header is still completely valid.
extstore_delete(storage, page_id, page_version, 1, ntotal);
// drop inactive items.
if (drop_unread && GET_LRU(hdr_it->slabs_clsid) == COLD_LRU) {
do_write = false;
skipped++;
} else {
do_write = true;
}
}
}
if (do_write) {
bool do_update = false;
int tries;
obj_io io;
io.len = ntotal;
io.mode = OBJ_IO_WRITE;
for (tries = 10; tries > 0; tries--) {
if (extstore_write_request(storage, PAGE_BUCKET_COMPACT, PAGE_BUCKET_COMPACT, &io) == 0) {
memcpy(io.buf, it, io.len);
extstore_write(storage, &io);
do_update = true;
break;
} else {
usleep(1000);
}
}
if (do_update) {
if (it->refcount == 2) {
hdr->page_version = io.page_version;
hdr->page_id = io.page_id;
hdr->offset = io.offset;
rescues++;
} else {
lost++;
// TODO: re-alloc and replace header.
}
} else {
lost++;
}
}
do_item_remove(hdr_it);
}
item_unlock(hv);
offset += ntotal;
if (read_size - offset < sizeof(struct _stritem))
break;
}
STATS_LOCK();
stats.extstore_compact_lost += lost;
stats.extstore_compact_rescues += rescues;
stats.extstore_compact_skipped += skipped;
STATS_UNLOCK();
LOGGER_LOG(l, LOG_SYSEVENTS, LOGGER_COMPACT_READ_END,
NULL, page_id, offset, rescues, lost, skipped);
}