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/* -*- Mode: C; tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
* Slabs memory allocation, based on powers-of-N. Slabs are up to 1MB in size
* and are divided into chunks. The chunk sizes start off at the size of the
* "item" structure plus space for a small key and value. They increase by
* a multiplier factor from there, up to half the maximum slab size. The last
* slab size is always 1MB, since that's the maximum item size allowed by the
* memcached protocol.
*/
#include "memcached.h"
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/signal.h>
#include <sys/resource.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <pthread.h>
/* powers-of-N allocation structures */
typedef struct {
unsigned int size; /* sizes of items */
unsigned int perslab; /* how many items per slab */
void *slots; /* list of item ptrs */
unsigned int sl_curr; /* total free items in list */
unsigned int slabs; /* how many slabs were allocated for this class */
void **slab_list; /* array of slab pointers */
unsigned int list_size; /* size of prev array */
unsigned int killing; /* index+1 of dying slab, or zero if none */
size_t requested; /* The number of requested bytes */
} slabclass_t;
static slabclass_t slabclass[MAX_NUMBER_OF_SLAB_CLASSES];
static size_t mem_limit = 0;
static size_t mem_malloced = 0;
static int power_largest;
static void *mem_base = NULL;
static void *mem_current = NULL;
static size_t mem_avail = 0;
/**
* Access to the slab allocator is protected by this lock
*/
static pthread_mutex_t slabs_lock = PTHREAD_MUTEX_INITIALIZER;
static pthread_mutex_t slabs_rebalance_lock = PTHREAD_MUTEX_INITIALIZER;
/*
* Forward Declarations
*/
static int do_slabs_newslab(const unsigned int id);
static void *memory_allocate(size_t size);
static void do_slabs_free(void *ptr, const size_t size, unsigned int id);
/* Preallocate as many slab pages as possible (called from slabs_init)
on start-up, so users don't get confused out-of-memory errors when
they do have free (in-slab) space, but no space to make new slabs.
if maxslabs is 18 (POWER_LARGEST - POWER_SMALLEST + 1), then all
slab types can be made. if max memory is less than 18 MB, only the
smaller ones will be made. */
static void slabs_preallocate (const unsigned int maxslabs);
/*
* Figures out which slab class (chunk size) is required to store an item of
* a given size.
*
* Given object size, return id to use when allocating/freeing memory for object
* 0 means error: can't store such a large object
*/
unsigned int slabs_clsid(const size_t size) {
int res = POWER_SMALLEST;
if (size == 0)
return 0;
while (size > slabclass[res].size)
if (res++ == power_largest) /* won't fit in the biggest slab */
return 0;
return res;
}
/**
* Determines the chunk sizes and initializes the slab class descriptors
* accordingly.
*/
void slabs_init(const size_t limit, const double factor, const bool prealloc) {
int i = POWER_SMALLEST - 1;
unsigned int size = sizeof(item) + settings.chunk_size;
mem_limit = limit;
if (prealloc) {
/* Allocate everything in a big chunk with malloc */
mem_base = malloc(mem_limit);
if (mem_base != NULL) {
mem_current = mem_base;
mem_avail = mem_limit;
} else {
fprintf(stderr, "Warning: Failed to allocate requested memory in"
" one large chunk.\nWill allocate in smaller chunks\n");
}
}
memset(slabclass, 0, sizeof(slabclass));
while (++i < POWER_LARGEST && size <= settings.item_size_max / factor) {
/* Make sure items are always n-byte aligned */
if (size % CHUNK_ALIGN_BYTES)
size += CHUNK_ALIGN_BYTES - (size % CHUNK_ALIGN_BYTES);
slabclass[i].size = size;
slabclass[i].perslab = settings.item_size_max / slabclass[i].size;
size *= factor;
if (settings.verbose > 1) {
fprintf(stderr, "slab class %3d: chunk size %9u perslab %7u\n",
i, slabclass[i].size, slabclass[i].perslab);
}
}
power_largest = i;
slabclass[power_largest].size = settings.item_size_max;
slabclass[power_largest].perslab = 1;
if (settings.verbose > 1) {
fprintf(stderr, "slab class %3d: chunk size %9u perslab %7u\n",
i, slabclass[i].size, slabclass[i].perslab);
}
/* for the test suite: faking of how much we've already malloc'd */
{
char *t_initial_malloc = getenv("T_MEMD_INITIAL_MALLOC");
if (t_initial_malloc) {
mem_malloced = (size_t)atol(t_initial_malloc);
}
}
if (prealloc) {
slabs_preallocate(power_largest);
}
}
static void slabs_preallocate (const unsigned int maxslabs) {
int i;
unsigned int prealloc = 0;
/* pre-allocate a 1MB slab in every size class so people don't get
confused by non-intuitive "SERVER_ERROR out of memory"
messages. this is the most common question on the mailing
list. if you really don't want this, you can rebuild without
these three lines. */
for (i = POWER_SMALLEST; i <= POWER_LARGEST; i++) {
if (++prealloc > maxslabs)
return;
if (do_slabs_newslab(i) == 0) {
fprintf(stderr, "Error while preallocating slab memory!\n"
"If using -L or other prealloc options, max memory must be "
"at least %d megabytes.\n", power_largest);
exit(1);
}
}
}
static int grow_slab_list (const unsigned int id) {
slabclass_t *p = &slabclass[id];
if (p->slabs == p->list_size) {
size_t new_size = (p->list_size != 0) ? p->list_size * 2 : 16;
void *new_list = realloc(p->slab_list, new_size * sizeof(void *));
if (new_list == 0) return 0;
p->list_size = new_size;
p->slab_list = new_list;
}
return 1;
}
static void split_slab_page_into_freelist(char *ptr, const unsigned int id) {
slabclass_t *p = &slabclass[id];
int x;
for (x = 0; x < p->perslab; x++) {
do_slabs_free(ptr, 0, id);
ptr += p->size;
}
}
static int do_slabs_newslab(const unsigned int id) {
slabclass_t *p = &slabclass[id];
int len = settings.slab_reassign ? settings.item_size_max
: p->size * p->perslab;
char *ptr;
if ((mem_limit && mem_malloced + len > mem_limit && p->slabs > 0) ||
(grow_slab_list(id) == 0) ||
((ptr = memory_allocate((size_t)len)) == 0)) {
MEMCACHED_SLABS_SLABCLASS_ALLOCATE_FAILED(id);
return 0;
}
memset(ptr, 0, (size_t)len);
split_slab_page_into_freelist(ptr, id);
p->slab_list[p->slabs++] = ptr;
mem_malloced += len;
MEMCACHED_SLABS_SLABCLASS_ALLOCATE(id);
return 1;
}
/*@null@*/
static void *do_slabs_alloc(const size_t size, unsigned int id) {
slabclass_t *p;
void *ret = NULL;
item *it = NULL;
if (id < POWER_SMALLEST || id > power_largest) {
MEMCACHED_SLABS_ALLOCATE_FAILED(size, 0);
return NULL;
}
p = &slabclass[id];
assert(p->sl_curr == 0 || ((item *)p->slots)->slabs_clsid == 0);
/* fail unless we have space at the end of a recently allocated page,
we have something on our freelist, or we could allocate a new page */
if (! (p->sl_curr != 0 || do_slabs_newslab(id) != 0)) {
/* We don't have more memory available */
ret = NULL;
} else if (p->sl_curr != 0) {
/* return off our freelist */
it = (item *)p->slots;
p->slots = it->next;
if (it->next) it->next->prev = 0;
p->sl_curr--;
ret = (void *)it;
}
if (ret) {
p->requested += size;
MEMCACHED_SLABS_ALLOCATE(size, id, p->size, ret);
} else {
MEMCACHED_SLABS_ALLOCATE_FAILED(size, id);
}
return ret;
}
static void do_slabs_free(void *ptr, const size_t size, unsigned int id) {
slabclass_t *p;
item *it;
assert(((item *)ptr)->slabs_clsid == 0);
assert(id >= POWER_SMALLEST && id <= power_largest);
if (id < POWER_SMALLEST || id > power_largest)
return;
MEMCACHED_SLABS_FREE(size, id, ptr);
p = &slabclass[id];
it = (item *)ptr;
it->it_flags |= ITEM_SLABBED;
it->prev = 0;
it->next = p->slots;
if (it->next) it->next->prev = it;
p->slots = it;
p->sl_curr++;
p->requested -= size;
return;
}
static int nz_strcmp(int nzlength, const char *nz, const char *z) {
int zlength=strlen(z);
return (zlength == nzlength) && (strncmp(nz, z, zlength) == 0) ? 0 : -1;
}
bool get_stats(const char *stat_type, int nkey, ADD_STAT add_stats, void *c) {
bool ret = true;
if (add_stats != NULL) {
if (!stat_type) {
/* prepare general statistics for the engine */
STATS_LOCK();
APPEND_STAT("bytes", "%llu", (unsigned long long)stats.curr_bytes);
APPEND_STAT("curr_items", "%u", stats.curr_items);
APPEND_STAT("total_items", "%u", stats.total_items);
STATS_UNLOCK();
item_stats_totals(add_stats, c);
} else if (nz_strcmp(nkey, stat_type, "items") == 0) {
item_stats(add_stats, c);
} else if (nz_strcmp(nkey, stat_type, "slabs") == 0) {
slabs_stats(add_stats, c);
} else if (nz_strcmp(nkey, stat_type, "sizes") == 0) {
item_stats_sizes(add_stats, c);
} else {
ret = false;
}
} else {
ret = false;
}
return ret;
}
/*@null@*/
static void do_slabs_stats(ADD_STAT add_stats, void *c) {
int i, total;
/* Get the per-thread stats which contain some interesting aggregates */
struct thread_stats thread_stats;
threadlocal_stats_aggregate(&thread_stats);
total = 0;
for(i = POWER_SMALLEST; i <= power_largest; i++) {
slabclass_t *p = &slabclass[i];
if (p->slabs != 0) {
uint32_t perslab, slabs;
slabs = p->slabs;
perslab = p->perslab;
char key_str[STAT_KEY_LEN];
char val_str[STAT_VAL_LEN];
int klen = 0, vlen = 0;
APPEND_NUM_STAT(i, "chunk_size", "%u", p->size);
APPEND_NUM_STAT(i, "chunks_per_page", "%u", perslab);
APPEND_NUM_STAT(i, "total_pages", "%u", slabs);
APPEND_NUM_STAT(i, "total_chunks", "%u", slabs * perslab);
APPEND_NUM_STAT(i, "used_chunks", "%u",
slabs*perslab - p->sl_curr);
APPEND_NUM_STAT(i, "free_chunks", "%u", p->sl_curr);
/* Stat is dead, but displaying zero instead of removing it. */
APPEND_NUM_STAT(i, "free_chunks_end", "%u", 0);
APPEND_NUM_STAT(i, "mem_requested", "%llu",
(unsigned long long)p->requested);
APPEND_NUM_STAT(i, "get_hits", "%llu",
(unsigned long long)thread_stats.slab_stats[i].get_hits);
APPEND_NUM_STAT(i, "cmd_set", "%llu",
(unsigned long long)thread_stats.slab_stats[i].set_cmds);
APPEND_NUM_STAT(i, "delete_hits", "%llu",
(unsigned long long)thread_stats.slab_stats[i].delete_hits);
APPEND_NUM_STAT(i, "incr_hits", "%llu",
(unsigned long long)thread_stats.slab_stats[i].incr_hits);
APPEND_NUM_STAT(i, "decr_hits", "%llu",
(unsigned long long)thread_stats.slab_stats[i].decr_hits);
APPEND_NUM_STAT(i, "cas_hits", "%llu",
(unsigned long long)thread_stats.slab_stats[i].cas_hits);
APPEND_NUM_STAT(i, "cas_badval", "%llu",
(unsigned long long)thread_stats.slab_stats[i].cas_badval);
APPEND_NUM_STAT(i, "touch_hits", "%llu",
(unsigned long long)thread_stats.slab_stats[i].touch_hits);
total++;
}
}
/* add overall slab stats and append terminator */
APPEND_STAT("active_slabs", "%d", total);
APPEND_STAT("total_malloced", "%llu", (unsigned long long)mem_malloced);
add_stats(NULL, 0, NULL, 0, c);
}
static void *memory_allocate(size_t size) {
void *ret;
if (mem_base == NULL) {
/* We are not using a preallocated large memory chunk */
ret = malloc(size);
} else {
ret = mem_current;
if (size > mem_avail) {
return NULL;
}
/* mem_current pointer _must_ be aligned!!! */
if (size % CHUNK_ALIGN_BYTES) {
size += CHUNK_ALIGN_BYTES - (size % CHUNK_ALIGN_BYTES);
}
mem_current = ((char*)mem_current) + size;
if (size < mem_avail) {
mem_avail -= size;
} else {
mem_avail = 0;
}
}
return ret;
}
void *slabs_alloc(size_t size, unsigned int id) {
void *ret;
pthread_mutex_lock(&slabs_lock);
ret = do_slabs_alloc(size, id);
pthread_mutex_unlock(&slabs_lock);
return ret;
}
void slabs_free(void *ptr, size_t size, unsigned int id) {
pthread_mutex_lock(&slabs_lock);
do_slabs_free(ptr, size, id);
pthread_mutex_unlock(&slabs_lock);
}
void slabs_stats(ADD_STAT add_stats, void *c) {
pthread_mutex_lock(&slabs_lock);
do_slabs_stats(add_stats, c);
pthread_mutex_unlock(&slabs_lock);
}
void slabs_adjust_mem_requested(unsigned int id, size_t old, size_t ntotal)
{
pthread_mutex_lock(&slabs_lock);
slabclass_t *p;
if (id < POWER_SMALLEST || id > power_largest) {
fprintf(stderr, "Internal error! Invalid slab class\n");
abort();
}
p = &slabclass[id];
p->requested = p->requested - old + ntotal;
pthread_mutex_unlock(&slabs_lock);
}
static pthread_cond_t maintenance_cond = PTHREAD_COND_INITIALIZER;
static pthread_cond_t slab_rebalance_cond = PTHREAD_COND_INITIALIZER;
static volatile int do_run_slab_thread = 1;
static volatile int do_run_slab_rebalance_thread = 1;
#define DEFAULT_SLAB_BULK_CHECK 1
int slab_bulk_check = DEFAULT_SLAB_BULK_CHECK;
static int slab_rebalance_start(void) {
slabclass_t *s_cls;
int no_go = 0;
pthread_mutex_lock(&cache_lock);
pthread_mutex_lock(&slabs_lock);
if (slab_rebal.s_clsid < POWER_SMALLEST ||
slab_rebal.s_clsid > power_largest ||
slab_rebal.d_clsid < POWER_SMALLEST ||
slab_rebal.d_clsid > power_largest ||
slab_rebal.s_clsid == slab_rebal.d_clsid)
no_go = -2;
s_cls = &slabclass[slab_rebal.s_clsid];
if (!grow_slab_list(slab_rebal.d_clsid)) {
no_go = -1;
}
if (s_cls->slabs < 2)
no_go = -3;
if (no_go != 0) {
pthread_mutex_unlock(&slabs_lock);
pthread_mutex_unlock(&cache_lock);
return no_go; /* Should use a wrapper function... */
}
s_cls->killing = 1;
slab_rebal.slab_start = s_cls->slab_list[s_cls->killing - 1];
slab_rebal.slab_end = (char *)slab_rebal.slab_start +
(s_cls->size * s_cls->perslab);
slab_rebal.slab_pos = slab_rebal.slab_start;
slab_rebal.done = 0;
/* Also tells do_item_get to search for items in this slab */
slab_rebalance_signal = 2;
if (settings.verbose > 1) {
fprintf(stderr, "Started a slab rebalance\n");
}
pthread_mutex_unlock(&slabs_lock);
pthread_mutex_unlock(&cache_lock);
STATS_LOCK();
stats.slab_reassign_running = true;
STATS_UNLOCK();
return 0;
}
enum move_status {
MOVE_PASS=0, MOVE_DONE, MOVE_BUSY, MOVE_LOCKED
};
/* refcount == 0 is safe since nobody can incr while cache_lock is held.
* refcount != 0 is impossible since flags/etc can be modified in other
* threads. instead, note we found a busy one and bail. logic in do_item_get
* will prevent busy items from continuing to be busy
*/
static int slab_rebalance_move(void) {
slabclass_t *s_cls;
int x;
int was_busy = 0;
int refcount = 0;
enum move_status status = MOVE_PASS;
pthread_mutex_lock(&cache_lock);
pthread_mutex_lock(&slabs_lock);
s_cls = &slabclass[slab_rebal.s_clsid];
for (x = 0; x < slab_bulk_check; x++) {
item *it = slab_rebal.slab_pos;
status = MOVE_PASS;
if (it->slabs_clsid != 255) {
void *hold_lock = NULL;
uint32_t hv = hash(ITEM_key(it), it->nkey, 0);
if ((hold_lock = item_trylock(hv)) == NULL) {
status = MOVE_LOCKED;
} else {
refcount = refcount_incr(&it->refcount);
if (refcount == 1) { /* item is unlinked, unused */
if (it->it_flags & ITEM_SLABBED) {
/* remove from slab freelist */
if (s_cls->slots == it) {
s_cls->slots = it->next;
}
if (it->next) it->next->prev = it->prev;
if (it->prev) it->prev->next = it->next;
s_cls->sl_curr--;
status = MOVE_DONE;
} else {
status = MOVE_BUSY;
}
} else if (refcount == 2) { /* item is linked but not busy */
if ((it->it_flags & ITEM_LINKED) != 0) {
do_item_unlink_nolock(it, hash(ITEM_key(it), it->nkey, 0));
status = MOVE_DONE;
} else {
/* refcount == 1 + !ITEM_LINKED means the item is being
* uploaded to, or was just unlinked but hasn't been freed
* yet. Let it bleed off on its own and try again later */
status = MOVE_BUSY;
}
} else {
if (settings.verbose > 2) {
fprintf(stderr, "Slab reassign hit a busy item: refcount: %d (%d -> %d)\n",
it->refcount, slab_rebal.s_clsid, slab_rebal.d_clsid);
}
status = MOVE_BUSY;
}
item_trylock_unlock(hold_lock);
}
}
switch (status) {
case MOVE_DONE:
it->refcount = 0;
it->it_flags = 0;
it->slabs_clsid = 255;
break;
case MOVE_BUSY:
refcount_decr(&it->refcount);
case MOVE_LOCKED:
slab_rebal.busy_items++;
was_busy++;
break;
case MOVE_PASS:
break;
}
slab_rebal.slab_pos = (char *)slab_rebal.slab_pos + s_cls->size;
if (slab_rebal.slab_pos >= slab_rebal.slab_end)
break;
}
if (slab_rebal.slab_pos >= slab_rebal.slab_end) {
/* Some items were busy, start again from the top */
if (slab_rebal.busy_items) {
slab_rebal.slab_pos = slab_rebal.slab_start;
slab_rebal.busy_items = 0;
} else {
slab_rebal.done++;
}
}
pthread_mutex_unlock(&slabs_lock);
pthread_mutex_unlock(&cache_lock);
return was_busy;
}
static void slab_rebalance_finish(void) {
slabclass_t *s_cls;
slabclass_t *d_cls;
pthread_mutex_lock(&cache_lock);
pthread_mutex_lock(&slabs_lock);
s_cls = &slabclass[slab_rebal.s_clsid];
d_cls = &slabclass[slab_rebal.d_clsid];
/* At this point the stolen slab is completely clear */
s_cls->slab_list[s_cls->killing - 1] =
s_cls->slab_list[s_cls->slabs - 1];
s_cls->slabs--;
s_cls->killing = 0;
memset(slab_rebal.slab_start, 0, (size_t)settings.item_size_max);
d_cls->slab_list[d_cls->slabs++] = slab_rebal.slab_start;
split_slab_page_into_freelist(slab_rebal.slab_start,
slab_rebal.d_clsid);
slab_rebal.done = 0;
slab_rebal.s_clsid = 0;
slab_rebal.d_clsid = 0;
slab_rebal.slab_start = NULL;
slab_rebal.slab_end = NULL;
slab_rebal.slab_pos = NULL;
slab_rebalance_signal = 0;
pthread_mutex_unlock(&slabs_lock);
pthread_mutex_unlock(&cache_lock);
STATS_LOCK();
stats.slab_reassign_running = false;
stats.slabs_moved++;
STATS_UNLOCK();
if (settings.verbose > 1) {
fprintf(stderr, "finished a slab move\n");
}
}
/* Return 1 means a decision was reached.
* Move to its own thread (created/destroyed as needed) once automover is more
* complex.
*/
static int slab_automove_decision(int *src, int *dst) {
static uint64_t evicted_old[POWER_LARGEST];
static unsigned int slab_zeroes[POWER_LARGEST];
static unsigned int slab_winner = 0;
static unsigned int slab_wins = 0;
uint64_t evicted_new[POWER_LARGEST];
uint64_t evicted_diff = 0;
uint64_t evicted_max = 0;
unsigned int highest_slab = 0;
unsigned int total_pages[POWER_LARGEST];
int i;
int source = 0;
int dest = 0;
static rel_time_t next_run;
/* Run less frequently than the slabmove tester. */
if (current_time >= next_run) {
next_run = current_time + 10;
} else {
return 0;
}
item_stats_evictions(evicted_new);
pthread_mutex_lock(&cache_lock);
for (i = POWER_SMALLEST; i < power_largest; i++) {
total_pages[i] = slabclass[i].slabs;
}
pthread_mutex_unlock(&cache_lock);
/* Find a candidate source; something with zero evicts 3+ times */
for (i = POWER_SMALLEST; i < power_largest; i++) {
evicted_diff = evicted_new[i] - evicted_old[i];
if (evicted_diff == 0 && total_pages[i] > 2) {
slab_zeroes[i]++;
if (source == 0 && slab_zeroes[i] >= 3)
source = i;
} else {
slab_zeroes[i] = 0;
if (evicted_diff > evicted_max) {
evicted_max = evicted_diff;
highest_slab = i;
}
}
evicted_old[i] = evicted_new[i];
}
/* Pick a valid destination */
if (slab_winner != 0 && slab_winner == highest_slab) {
slab_wins++;
if (slab_wins >= 3)
dest = slab_winner;
} else {
slab_wins = 1;
slab_winner = highest_slab;
}
if (source && dest) {
*src = source;
*dst = dest;
return 1;
}
return 0;
}
/* Slab rebalancer thread.
* Does not use spinlocks since it is not timing sensitive. Burn less CPU and
* go to sleep if locks are contended
*/
static void *slab_maintenance_thread(void *arg) {
int src, dest;
while (do_run_slab_thread) {
if (settings.slab_automove == 1) {
if (slab_automove_decision(&src, &dest) == 1) {
/* Blind to the return codes. It will retry on its own */
slabs_reassign(src, dest);
}
sleep(1);
} else {
/* Don't wake as often if we're not enabled.
* This is lazier than setting up a condition right now. */
sleep(5);
}
}
return NULL;
}
/* Slab mover thread.
* Sits waiting for a condition to jump off and shovel some memory about
*/
static void *slab_rebalance_thread(void *arg) {
int was_busy = 0;
/* So we first pass into cond_wait with the mutex held */
mutex_lock(&slabs_rebalance_lock);
while (do_run_slab_rebalance_thread) {
if (slab_rebalance_signal == 1) {
if (slab_rebalance_start() < 0) {
/* Handle errors with more specifity as required. */
slab_rebalance_signal = 0;
}
was_busy = 0;
} else if (slab_rebalance_signal && slab_rebal.slab_start != NULL) {
was_busy = slab_rebalance_move();
}
if (slab_rebal.done) {
slab_rebalance_finish();
} else if (was_busy) {
/* Stuck waiting for some items to unlock, so slow down a bit
* to give them a chance to free up */
usleep(50);
}
if (slab_rebalance_signal == 0) {
/* always hold this lock while we're running */
pthread_cond_wait(&slab_rebalance_cond, &slabs_rebalance_lock);
}
}
return NULL;
}
/* Iterate at most once through the slab classes and pick a "random" source.
* I like this better than calling rand() since rand() is slow enough that we
* can just check all of the classes once instead.
*/
static int slabs_reassign_pick_any(int dst) {
static int cur = POWER_SMALLEST - 1;
int tries = power_largest - POWER_SMALLEST + 1;
for (; tries > 0; tries--) {
cur++;
if (cur > power_largest)
cur = POWER_SMALLEST;
if (cur == dst)
continue;
if (slabclass[cur].slabs > 1) {
return cur;
}
}
return -1;
}
static enum reassign_result_type do_slabs_reassign(int src, int dst) {
if (slab_rebalance_signal != 0)
return REASSIGN_RUNNING;
if (src == dst)
return REASSIGN_SRC_DST_SAME;
/* Special indicator to choose ourselves. */
if (src == -1) {
src = slabs_reassign_pick_any(dst);
/* TODO: If we end up back at -1, return a new error type */
}
if (src < POWER_SMALLEST || src > power_largest ||
dst < POWER_SMALLEST || dst > power_largest)
return REASSIGN_BADCLASS;
if (slabclass[src].slabs < 2)
return REASSIGN_NOSPARE;
slab_rebal.s_clsid = src;
slab_rebal.d_clsid = dst;
slab_rebalance_signal = 1;
pthread_cond_signal(&slab_rebalance_cond);
return REASSIGN_OK;
}
enum reassign_result_type slabs_reassign(int src, int dst) {
enum reassign_result_type ret;
if (pthread_mutex_trylock(&slabs_rebalance_lock) != 0) {
return REASSIGN_RUNNING;
}
ret = do_slabs_reassign(src, dst);
pthread_mutex_unlock(&slabs_rebalance_lock);
return ret;
}
/* If we hold this lock, rebalancer can't wake up or move */
void slabs_rebalancer_pause(void) {
pthread_mutex_lock(&slabs_rebalance_lock);
}
void slabs_rebalancer_resume(void) {
pthread_mutex_unlock(&slabs_rebalance_lock);
}
static pthread_t maintenance_tid;
static pthread_t rebalance_tid;
int start_slab_maintenance_thread(void) {
int ret;
slab_rebalance_signal = 0;
slab_rebal.slab_start = NULL;
char *env = getenv("MEMCACHED_SLAB_BULK_CHECK");
if (env != NULL) {
slab_bulk_check = atoi(env);
if (slab_bulk_check == 0) {
slab_bulk_check = DEFAULT_SLAB_BULK_CHECK;
}
}
if (pthread_cond_init(&slab_rebalance_cond, NULL) != 0) {
fprintf(stderr, "Can't intiialize rebalance condition\n");
return -1;
}
pthread_mutex_init(&slabs_rebalance_lock, NULL);
if ((ret = pthread_create(&maintenance_tid, NULL,
slab_maintenance_thread, NULL)) != 0) {
fprintf(stderr, "Can't create slab maint thread: %s\n", strerror(ret));
return -1;
}
if ((ret = pthread_create(&rebalance_tid, NULL,
slab_rebalance_thread, NULL)) != 0) {
fprintf(stderr, "Can't create rebal thread: %s\n", strerror(ret));
return -1;
}
return 0;
}
void stop_slab_maintenance_thread(void) {
mutex_lock(&cache_lock);
do_run_slab_thread = 0;
do_run_slab_rebalance_thread = 0;
pthread_cond_signal(&maintenance_cond);
pthread_mutex_unlock(&cache_lock);
/* Wait for the maintenance thread to stop */
pthread_join(maintenance_tid, NULL);
pthread_join(rebalance_tid, NULL);
}
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