/* -*- Mode: C; tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/* $Id$ */
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <sys/signal.h>
#include <sys/resource.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include <errno.h>
#include <time.h>
#include <event.h>
#include <assert.h>
#include "memcached.h"
/*
* 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
#define LARGEST_ID 255
static item *heads[LARGEST_ID];
static item *tails[LARGEST_ID];
unsigned int sizes[LARGEST_ID];
void item_init(void) {
int i;
for(i=0; i<LARGEST_ID; i++) {
heads[i]=0;
tails[i]=0;
sizes[i]=0;
}
}
/*
* Generates the variable-sized part of the header for an object.
*
* key - The key
* nkey - The length of the key
* flags - key flags
* nbytes - Number of bytes to hold value and addition CRLF terminator
* suffix - Buffer for the "VALUE" line suffix (flags, size).
* nsuffix - The length of the suffix is stored here.
*
* Returns the total size of the header.
*/
int item_make_header(char *key, uint8_t nkey, int flags, int nbytes,
char *suffix, int *nsuffix) {
*nsuffix = sprintf(suffix, " %u %u\r\n", flags, nbytes - 2);
return sizeof(item) + nkey + *nsuffix + nbytes;
}
item *item_alloc(char *key, size_t nkey, int flags, rel_time_t exptime, int nbytes) {
int nsuffix, ntotal;
item *it;
unsigned int id;
char suffix[40];
ntotal = item_make_header(key, nkey + 1, flags, nbytes, suffix, &nsuffix);
id = slabs_clsid(ntotal);
if (id == 0)
return 0;
it = slabs_alloc(ntotal);
if (it == 0) {
int tries = 50;
item *search;
/* If requested to not push old items out of cache when memory runs out,
* we're out of luck at this point...
*/
if (!settings.evict_to_free) return 0;
/*
* 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
*/
if (id > LARGEST_ID) return 0;
if (tails[id]==0) return 0;
for (search = tails[id]; tries>0 && search; tries--, search=search->prev) {
if (search->refcount==0) {
item_unlink(search);
break;
}
}
it = slabs_alloc(ntotal);
if (it==0) return 0;
}
assert(it->slabs_clsid == 0);
it->slabs_clsid = id;
assert(it != heads[it->slabs_clsid]);
it->next = it->prev = it->h_next = 0;
it->refcount = 0;
it->it_flags = 0;
it->nkey = nkey;
it->nbytes = nbytes;
strcpy(ITEM_key(it), key);
it->exptime = exptime;
memcpy(ITEM_suffix(it), suffix, nsuffix);
it->nsuffix = nsuffix;
return it;
}
void item_free(item *it) {
unsigned int ntotal = ITEM_ntotal(it);
assert((it->it_flags & ITEM_LINKED) == 0);
assert(it != heads[it->slabs_clsid]);
assert(it != tails[it->slabs_clsid]);
assert(it->refcount == 0);
/* so slab size changer can tell later if item is already free or not */
it->slabs_clsid = 0;
it->it_flags |= ITEM_SLABBED;
slabs_free(it, ntotal);
}
/*
* Returns true if an item will fit in the cache (its size does not exceed
* the maximum for a cache entry.)
*/
int item_size_ok(char *key, size_t nkey, int flags, int nbytes) {
char prefix[40];
int nsuffix;
return slabs_clsid(item_make_header(key, nkey + 1, flags, nbytes,
prefix, &nsuffix)) != 0;
}
void item_link_q(item *it) { /* item is the new head */
item **head, **tail;
/* always true, warns: assert(it->slabs_clsid <= LARGEST_ID); */
assert((it->it_flags & ITEM_SLABBED) == 0);
head = &heads[it->slabs_clsid];
tail = &tails[it->slabs_clsid];
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;
sizes[it->slabs_clsid]++;
return;
}
void item_unlink_q(item *it) {
item **head, **tail;
/* always true, warns: assert(it->slabs_clsid <= LARGEST_ID); */
head = &heads[it->slabs_clsid];
tail = &tails[it->slabs_clsid];
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;
sizes[it->slabs_clsid]--;
return;
}
int item_link(item *it) {
assert((it->it_flags & (ITEM_LINKED|ITEM_SLABBED)) == 0);
assert(it->nbytes < 1048576);
it->it_flags |= ITEM_LINKED;
it->time = current_time;
assoc_insert(it);
stats.curr_bytes += ITEM_ntotal(it);
stats.curr_items += 1;
stats.total_items += 1;
item_link_q(it);
return 1;
}
void item_unlink(item *it) {
if (it->it_flags & ITEM_LINKED) {
it->it_flags &= ~ITEM_LINKED;
stats.curr_bytes -= ITEM_ntotal(it);
stats.curr_items -= 1;
assoc_delete(ITEM_key(it), it->nkey);
item_unlink_q(it);
}
if (it->refcount == 0) item_free(it);
}
void item_remove(item *it) {
assert((it->it_flags & ITEM_SLABBED) == 0);
if (it->refcount) it->refcount--;
assert((it->it_flags & ITEM_DELETED) == 0 || it->refcount);
if (it->refcount == 0 && (it->it_flags & ITEM_LINKED) == 0) {
item_free(it);
}
}
void item_update(item *it) {
if (it->time < current_time - ITEM_UPDATE_INTERVAL) {
assert((it->it_flags & ITEM_SLABBED) == 0);
item_unlink_q(it);
it->time = current_time;
item_link_q(it);
}
}
int item_replace(item *it, item *new_it) {
assert((it->it_flags & ITEM_SLABBED) == 0);
item_unlink(it);
return item_link(new_it);
}
char *item_cachedump(unsigned int slabs_clsid, unsigned int limit, unsigned int *bytes) {
int memlimit = 2*1024*1024;
char *buffer;
int bufcurr;
item *it;
int len;
int shown = 0;
char temp[512];
if (slabs_clsid > LARGEST_ID) return 0;
it = heads[slabs_clsid];
buffer = malloc(memlimit);
if (buffer == 0) return 0;
bufcurr = 0;
while (it && (!limit || shown < limit)) {
len = sprintf(temp, "ITEM %s [%u b; %lu s]\r\n", ITEM_key(it), it->nbytes - 2, it->time + stats.started);
if (bufcurr + len + 6 > memlimit) /* 6 is END\r\n\0 */
break;
strcpy(buffer + bufcurr, temp);
bufcurr+=len;
shown++;
it = it->next;
}
strcpy(buffer+bufcurr, "END\r\n");
bufcurr+=5;
*bytes = bufcurr;
return buffer;
}
void item_stats(char *buffer, int buflen) {
int i;
char *bufcurr = buffer;
rel_time_t now = current_time;
if (buflen < 4096) {
strcpy(buffer, "SERVER_ERROR out of memory");
return;
}
for (i=0; i<LARGEST_ID; i++) {
if (tails[i])
bufcurr += sprintf(bufcurr, "STAT items:%u:number %u\r\nSTAT items:%u:age %u\r\n",
i, sizes[i], i, now - tails[i]->time);
}
strcpy(bufcurr, "END");
return;
}
/* dumps out a list of objects of each size, with granularity of 32 bytes */
char* item_stats_sizes(int *bytes) {
int num_buckets = 32768; /* max 1MB object, divided into 32 bytes size buckets */
unsigned int *histogram = (unsigned int*) malloc(num_buckets * sizeof(int));
char *buf = (char*) malloc(1024*1024*2*sizeof(char));
int i;
if (histogram == 0 || buf == 0) {
if (histogram) free(histogram);
if (buf) free(buf);
return 0;
}
/* build the histogram */
memset(histogram, 0, num_buckets * sizeof(int));
for (i=0; i<LARGEST_ID; i++) {
item *iter = heads[i];
while (iter) {
int ntotal = ITEM_ntotal(iter);
int bucket = ntotal / 32;
if (ntotal % 32) bucket++;
if (bucket < num_buckets) histogram[bucket]++;
iter = iter->next;
}
}
/* write the buffer */
*bytes = 0;
for (i=0; i<num_buckets; i++) {
if (histogram[i]) {
*bytes += sprintf(&buf[*bytes], "%u %u\r\n", i*32, histogram[i]);
}
}
*bytes += sprintf(&buf[*bytes], "END\r\n");
free(histogram);
return buf;
}
/* expires items that are more recent than the oldest_live setting. */
void item_flush_expired() {
int i;
item *iter, *next;
if (! settings.oldest_live)
return;
for (i = 0; i < LARGEST_ID; i++) {
/* The LRU is sorted in decreasing time order, and an item's timestamp
* is never newer than its last access time, so we only need to walk
* back until we hit an item older than the oldest_live time.
* The oldest_live checking will auto-expire the remaining items.
*/
for (iter = heads[i]; iter != NULL; iter = next) {
if (iter->time >= settings.oldest_live) {
next = iter->next;
if ((iter->it_flags & ITEM_SLABBED) == 0) {
item_unlink(iter);
}
} else {
/* We've hit the first old item. Continue to the next queue. */
break;
}
}
}
}
