* documentation. */
/* TODO:
+ *
+ * WARNING: most of the following todo items and design issues are no
+ * longer relevant with the new design. Here as a checklist to see if
+ * some old ideas still apply.
*
* - The WATCH helper will be used to signal the cache system
* we need to flush a given key/dbid into disk, adding this key/dbid
* - What happens with MULTI/EXEC?
*
* Good question.
+ *
+ * - If dsSet() fails on the write thread log the error and reschedule the
+ * key for flush.
+ *
+ * - Check why INCR will not update the LRU info for the object.
+ *
+ * - Fix/Check the following race condition: a key gets a DEL so there is
+ * a write operation scheduled against this key. Later the same key will
+ * be the argument of a GET, but the write operation was still not
+ * completed (to delete the file). If the GET will be for some reason
+ * a blocking loading (via lookup) we can load the old value on memory.
+ *
+ * This problems can be fixed with negative caching. We can use it
+ * to optimize the system, but also when a key is deleted we mark
+ * it as non existing on disk as well (in a way that this cache
+ * entry can't be evicted, setting time to 0), then we avoid looking at
+ * the disk at all if the key can't be there. When an IO Job complete
+ * a deletion, we set the time of the negative caching to a non zero
+ * value so it will be evicted later.
+ *
+ * Are there other patterns like this where we load stale data?
+ *
+ * Also, make sure that key preloading is ONLY done for keys that are
+ * not marked as cacheKeyDoesNotExist(), otherwise, again, we can load
+ * data from disk that should instead be deleted.
+ *
+ * - dsSet() use rename(2) in order to avoid corruptions.
*/
/* Virtual Memory is composed mainly of two subsystems:
* as a fully non-blocking VM.
*/
+void spawnIOThread(void);
+
/* =================== Virtual Memory - Blocking Side ====================== */
-void vmInit(void) {
- off_t totsize;
+void dsInit(void) {
int pipefds[2];
size_t stacksize;
- struct flock fl;
- if (server.vm_max_threads != 0)
- zmalloc_enable_thread_safeness(); /* we need thread safe zmalloc() */
+ zmalloc_enable_thread_safeness(); /* we need thread safe zmalloc() */
- redisLog(REDIS_NOTICE,"Using '%s' as swap file",server.vm_swap_file);
- /* Try to open the old swap file, otherwise create it */
- if ((server.vm_fp = fopen(server.vm_swap_file,"r+b")) == NULL) {
- server.vm_fp = fopen(server.vm_swap_file,"w+b");
- }
- if (server.vm_fp == NULL) {
- redisLog(REDIS_WARNING,
- "Can't open the swap file: %s. Exiting.",
- strerror(errno));
+ redisLog(REDIS_NOTICE,"Opening Disk Store: %s", server.ds_path);
+ /* Open Disk Store */
+ if (dsOpen() != REDIS_OK) {
+ redisLog(REDIS_WARNING,"Fatal error opening disk store. Exiting.");
exit(1);
- }
- server.vm_fd = fileno(server.vm_fp);
- /* Lock the swap file for writing, this is useful in order to avoid
- * another instance to use the same swap file for a config error. */
- fl.l_type = F_WRLCK;
- fl.l_whence = SEEK_SET;
- fl.l_start = fl.l_len = 0;
- if (fcntl(server.vm_fd,F_SETLK,&fl) == -1) {
- redisLog(REDIS_WARNING,
- "Can't lock the swap file at '%s': %s. Make sure it is not used by another Redis instance.", server.vm_swap_file, strerror(errno));
- exit(1);
- }
- /* Initialize */
- server.vm_next_page = 0;
- server.vm_near_pages = 0;
- server.vm_stats_used_pages = 0;
- server.vm_stats_swapped_objects = 0;
- server.vm_stats_swapouts = 0;
- server.vm_stats_swapins = 0;
- totsize = server.vm_pages*server.vm_page_size;
- redisLog(REDIS_NOTICE,"Allocating %lld bytes of swap file",totsize);
- if (ftruncate(server.vm_fd,totsize) == -1) {
- redisLog(REDIS_WARNING,"Can't ftruncate swap file: %s. Exiting.",
- strerror(errno));
- exit(1);
- } else {
- redisLog(REDIS_NOTICE,"Swap file allocated with success");
- }
- server.vm_bitmap = zcalloc((server.vm_pages+7)/8);
- redisLog(REDIS_VERBOSE,"Allocated %lld bytes page table for %lld pages",
- (long long) (server.vm_pages+7)/8, server.vm_pages);
+ };
- /* Initialize threaded I/O (used by Virtual Memory) */
+ /* Initialize threaded I/O for Object Cache */
server.io_newjobs = listCreate();
server.io_processing = listCreate();
server.io_processed = listCreate();
server.io_ready_clients = listCreate();
pthread_mutex_init(&server.io_mutex,NULL);
- pthread_mutex_init(&server.io_swapfile_mutex,NULL);
+ pthread_cond_init(&server.io_condvar,NULL);
server.io_active_threads = 0;
if (pipe(pipefds) == -1) {
- redisLog(REDIS_WARNING,"Unable to intialized VM: pipe(2): %s. Exiting."
+ redisLog(REDIS_WARNING,"Unable to intialized DS: pipe(2): %s. Exiting."
,strerror(errno));
exit(1);
}
if (aeCreateFileEvent(server.el, server.io_ready_pipe_read, AE_READABLE,
vmThreadedIOCompletedJob, NULL) == AE_ERR)
oom("creating file event");
-}
-
-/* Write the specified object at the specified page of the swap file */
-int vmWriteObjectOnSwap(robj *o, off_t page) {
- if (server.vm_enabled) pthread_mutex_lock(&server.io_swapfile_mutex);
- if (fseeko(server.vm_fp,page*server.vm_page_size,SEEK_SET) == -1) {
- if (server.vm_enabled) pthread_mutex_unlock(&server.io_swapfile_mutex);
- redisLog(REDIS_WARNING,
- "Critical VM problem in vmWriteObjectOnSwap(): can't seek: %s",
- strerror(errno));
- return REDIS_ERR;
- }
- rdbSaveObject(server.vm_fp,o);
- fflush(server.vm_fp);
- if (server.vm_enabled) pthread_mutex_unlock(&server.io_swapfile_mutex);
- return REDIS_OK;
-}
-
-/* Transfers the 'val' object to disk. Store all the information
- * a 'vmpointer' object containing all the information needed to load the
- * object back later is returned.
- *
- * If we can't find enough contiguous empty pages to swap the object on disk
- * NULL is returned. */
-vmpointer *vmSwapObjectBlocking(robj *val) {
- off_t pages = rdbSavedObjectPages(val);
- off_t page;
- vmpointer *vp;
-
- redisAssert(val->storage == REDIS_VM_MEMORY);
- redisAssert(val->refcount == 1);
- if (vmFindContiguousPages(&page,pages) == REDIS_ERR) return NULL;
- if (vmWriteObjectOnSwap(val,page) == REDIS_ERR) return NULL;
-
- vp = createVmPointer(val->type);
- vp->page = page;
- vp->usedpages = pages;
- decrRefCount(val); /* Deallocate the object from memory. */
- vmMarkPagesUsed(page,pages);
- redisLog(REDIS_DEBUG,"VM: object %p swapped out at %lld (%lld pages)",
- (void*) val,
- (unsigned long long) page, (unsigned long long) pages);
- server.vm_stats_swapped_objects++;
- server.vm_stats_swapouts++;
- return vp;
-}
-
-robj *vmReadObjectFromSwap(off_t page, int type) {
- robj *o;
-
- if (server.vm_enabled) pthread_mutex_lock(&server.io_swapfile_mutex);
- if (fseeko(server.vm_fp,page*server.vm_page_size,SEEK_SET) == -1) {
- redisLog(REDIS_WARNING,
- "Unrecoverable VM problem in vmReadObjectFromSwap(): can't seek: %s",
- strerror(errno));
- _exit(1);
- }
- o = rdbLoadObject(type,server.vm_fp);
- if (o == NULL) {
- redisLog(REDIS_WARNING, "Unrecoverable VM problem in vmReadObjectFromSwap(): can't load object from swap file: %s", strerror(errno));
- _exit(1);
- }
- if (server.vm_enabled) pthread_mutex_unlock(&server.io_swapfile_mutex);
- return o;
-}
-
-/* Load the specified object from swap to memory.
- * The newly allocated object is returned.
- *
- * If preview is true the unserialized object is returned to the caller but
- * the pages are not marked as freed, nor the vp object is freed. */
-robj *vmGenericLoadObject(vmpointer *vp, int preview) {
- robj *val;
-
- redisAssert(vp->type == REDIS_VMPOINTER &&
- (vp->storage == REDIS_VM_SWAPPED || vp->storage == REDIS_VM_LOADING));
- val = vmReadObjectFromSwap(vp->page,vp->vtype);
- if (!preview) {
- redisLog(REDIS_DEBUG, "VM: object %p loaded from disk", (void*)vp);
- vmMarkPagesFree(vp->page,vp->usedpages);
- zfree(vp);
- server.vm_stats_swapped_objects--;
- } else {
- redisLog(REDIS_DEBUG, "VM: object %p previewed from disk", (void*)vp);
- }
- server.vm_stats_swapins++;
- return val;
-}
-
-/* Plain object loading, from swap to memory.
- *
- * 'o' is actually a redisVmPointer structure that will be freed by the call.
- * The return value is the loaded object. */
-robj *vmLoadObject(robj *o) {
- /* If we are loading the object in background, stop it, we
- * need to load this object synchronously ASAP. */
- if (o->storage == REDIS_VM_LOADING)
- vmCancelThreadedIOJob(o);
- return vmGenericLoadObject((vmpointer*)o,0);
-}
-/* Just load the value on disk, without to modify the key.
- * This is useful when we want to perform some operation on the value
- * without to really bring it from swap to memory, like while saving the
- * dataset or rewriting the append only log. */
-robj *vmPreviewObject(robj *o) {
- return vmGenericLoadObject((vmpointer*)o,1);
+ /* Spawn our I/O thread */
+ spawnIOThread();
}
-/* How a good candidate is this object for swapping?
- * The better candidate it is, the greater the returned value.
- *
- * Currently we try to perform a fast estimation of the object size in
- * memory, and combine it with aging informations.
- *
- * Basically swappability = idle-time * log(estimated size)
- *
- * Bigger objects are preferred over smaller objects, but not
- * proportionally, this is why we use the logarithm. This algorithm is
- * just a first try and will probably be tuned later. */
+/* Compute how good candidate the specified object is for eviction.
+ * An higher number means a better candidate. */
double computeObjectSwappability(robj *o) {
/* actual age can be >= minage, but not < minage. As we use wrapping
* 21 bit clocks with minutes resolution for the LRU. */
return (double) estimateObjectIdleTime(o);
}
-/* Try to swap an object that's a good candidate for swapping.
- * Returns REDIS_OK if the object was swapped, REDIS_ERR if it's not possible
- * to swap any object at all.
- *
- * If 'usethreaded' is true, Redis will try to swap the object in background
- * using I/O threads. */
-int vmSwapOneObject(int usethreads) {
+/* Try to free one entry from the diskstore object cache */
+int cacheFreeOneEntry(void) {
int j, i;
struct dictEntry *best = NULL;
double best_swappability = 0;
for (i = 0; i < 5; i++) {
dictEntry *de;
double swappability;
+ robj keyobj;
+ sds keystr;
if (maxtries) maxtries--;
de = dictGetRandomKey(db->dict);
+ keystr = dictGetEntryKey(de);
val = dictGetEntryVal(de);
- /* Only swap objects that are currently in memory.
- *
- * Also don't swap shared objects: not a good idea in general and
- * we need to ensure that the main thread does not touch the
- * object while the I/O thread is using it, but we can't
- * control other keys without adding additional mutex. */
- if (val->storage != REDIS_VM_MEMORY || val->refcount != 1) {
+ initStaticStringObject(keyobj,keystr);
+
+ /* Don't remove objects that are currently target of a
+ * read or write operation. */
+ if (cacheScheduleIOGetFlags(db,&keyobj) != 0) {
if (maxtries) i--; /* don't count this try */
continue;
}
}
}
}
- if (best == NULL) return REDIS_ERR;
+ if (best == NULL) {
+ /* FIXME: If there are objects marked as DS_DIRTY or DS_SAVING
+ * let's wait for this objects to be clear and retry...
+ *
+ * Object cache vm limit is considered an hard limit. */
+ return REDIS_ERR;
+ }
key = dictGetEntryKey(best);
val = dictGetEntryVal(best);
- redisLog(REDIS_DEBUG,"Key with best swappability: %s, %f",
+ redisLog(REDIS_DEBUG,"Key selected for cache eviction: %s swappability:%f",
key, best_swappability);
- /* Swap it */
- if (usethreads) {
- robj *keyobj = createStringObject(key,sdslen(key));
- vmSwapObjectThreaded(keyobj,val,best_db);
- decrRefCount(keyobj);
- return REDIS_OK;
- } else {
- vmpointer *vp;
-
- if ((vp = vmSwapObjectBlocking(val)) != NULL) {
- dictGetEntryVal(best) = vp;
- return REDIS_OK;
- } else {
- return REDIS_ERR;
- }
+ /* Delete this key from memory */
+ {
+ robj *kobj = createStringObject(key,sdslen(key));
+ dbDelete(best_db,kobj);
+ decrRefCount(kobj);
}
-}
-
-int vmSwapOneObjectBlocking() {
- return vmSwapOneObject(0);
-}
-
-int vmSwapOneObjectThreaded() {
- return vmSwapOneObject(1);
+ return REDIS_OK;
}
/* Return true if it's safe to swap out objects in a given moment.
* Basically we don't want to swap objects out while there is a BGSAVE
* or a BGAEOREWRITE running in backgroud. */
-int vmCanSwapOut(void) {
+int dsCanTouchDiskStore(void) {
return (server.bgsavechildpid == -1 && server.bgrewritechildpid == -1);
}
-/* =================== Virtual Memory - Threaded I/O ======================= */
+/* ==================== Disk store negative caching ========================
+ *
+ * When disk store is enabled, we need negative caching, that is, to remember
+ * keys that are for sure *not* on the disk key-value store.
+ *
+ * This is usefuls because without negative caching cache misses will cost us
+ * a disk lookup, even if the same non existing key is accessed again and again.
+ *
+ * With negative caching we remember that the key is not on disk, so if it's
+ * not in memory and we have a negative cache entry, we don't try a disk
+ * access at all.
+ */
-void freeIOJob(iojob *j) {
- if ((j->type == REDIS_IOJOB_PREPARE_SWAP ||
- j->type == REDIS_IOJOB_DO_SWAP ||
- j->type == REDIS_IOJOB_LOAD) && j->val != NULL)
- {
- /* we fix the storage type, otherwise decrRefCount() will try to
- * kill the I/O thread Job (that does no longer exists). */
- if (j->val->storage == REDIS_VM_SWAPPING)
- j->val->storage = REDIS_VM_MEMORY;
- decrRefCount(j->val);
+/* Returns true if the specified key may exists on disk, that is, we don't
+ * have an entry in our negative cache for this key */
+int cacheKeyMayExist(redisDb *db, robj *key) {
+ return dictFind(db->io_negcache,key) == NULL;
+}
+
+/* Set the specified key as an entry that may possibily exist on disk, that is,
+ * remove the negative cache entry for this key if any. */
+void cacheSetKeyMayExist(redisDb *db, robj *key) {
+ dictDelete(db->io_negcache,key);
+}
+
+/* Set the specified key as non existing on disk, that is, create a negative
+ * cache entry for this key. */
+void cacheSetKeyDoesNotExist(redisDb *db, robj *key) {
+ if (dictReplace(db->io_negcache,key,(void*)time(NULL))) {
+ incrRefCount(key);
}
+}
+
+/* ================== Disk store cache - Threaded I/O ====================== */
+
+void freeIOJob(iojob *j) {
decrRefCount(j->key);
+ /* j->val can be NULL if the job is about deleting the key from disk. */
+ if (j->val) decrRefCount(j->val);
zfree(j);
}
/* Every time a thread finished a Job, it writes a byte into the write side
* of an unix pipe in order to "awake" the main thread, and this function
- * is called.
- *
- * Note that this is called both by the event loop, when a I/O thread
- * sends a byte in the notification pipe, and is also directly called from
- * waitEmptyIOJobsQueue().
- *
- * In the latter case we don't want to swap more, so we use the
- * "privdata" argument setting it to a not NULL value to signal this
- * condition. */
+ * is called. */
void vmThreadedIOCompletedJob(aeEventLoop *el, int fd, void *privdata,
int mask)
{
char buf[1];
- int retval, processed = 0, toprocess = -1, trytoswap = 1;
+ int retval, processed = 0, toprocess = -1;
REDIS_NOTUSED(el);
REDIS_NOTUSED(mask);
REDIS_NOTUSED(privdata);
- if (privdata != NULL) trytoswap = 0; /* check the comments above... */
-
/* For every byte we read in the read side of the pipe, there is one
* I/O job completed to process. */
while((retval = read(fd,buf,1)) == 1) {
iojob *j;
listNode *ln;
- struct dictEntry *de;
redisLog(REDIS_DEBUG,"Processing I/O completed job");
j = ln->value;
listDelNode(server.io_processed,ln);
unlockThreadedIO();
- /* If this job is marked as canceled, just ignore it */
- if (j->canceled) {
- freeIOJob(j);
- continue;
- }
+
/* Post process it in the main thread, as there are things we
* can do just here to avoid race conditions and/or invasive locks */
- redisLog(REDIS_DEBUG,"COMPLETED Job type: %d, ID %p, key: %s", j->type, (void*)j->id, (unsigned char*)j->key->ptr);
- de = dictFind(j->db->dict,j->key->ptr);
- redisAssert(de != NULL);
+ redisLog(REDIS_DEBUG,"COMPLETED Job type %s, key: %s",
+ (j->type == REDIS_IOJOB_LOAD) ? "load" : "save",
+ (unsigned char*)j->key->ptr);
if (j->type == REDIS_IOJOB_LOAD) {
- redisDb *db;
- vmpointer *vp = dictGetEntryVal(de);
-
- /* Key loaded, bring it at home */
- vmMarkPagesFree(vp->page,vp->usedpages);
- redisLog(REDIS_DEBUG, "VM: object %s loaded from disk (threaded)",
- (unsigned char*) j->key->ptr);
- server.vm_stats_swapped_objects--;
- server.vm_stats_swapins++;
- dictGetEntryVal(de) = j->val;
- incrRefCount(j->val);
- db = j->db;
- /* Handle clients waiting for this key to be loaded. */
- handleClientsBlockedOnSwappedKey(db,j->key);
- freeIOJob(j);
- zfree(vp);
- } else if (j->type == REDIS_IOJOB_PREPARE_SWAP) {
- /* Now we know the amount of pages required to swap this object.
- * Let's find some space for it, and queue this task again
- * rebranded as REDIS_IOJOB_DO_SWAP. */
- if (!vmCanSwapOut() ||
- vmFindContiguousPages(&j->page,j->pages) == REDIS_ERR)
- {
- /* Ooops... no space or we can't swap as there is
- * a fork()ed Redis trying to save stuff on disk. */
- j->val->storage = REDIS_VM_MEMORY; /* undo operation */
- freeIOJob(j);
+ /* Create the key-value pair in the in-memory database */
+ if (j->val != NULL) {
+ /* Note: it's possible that the key is already in memory
+ * due to a blocking load operation. */
+ if (dbAdd(j->db,j->key,j->val) == REDIS_OK) {
+ incrRefCount(j->val);
+ if (j->expire != -1) setExpire(j->db,j->key,j->expire);
+ }
} else {
- /* Note that we need to mark this pages as used now,
- * if the job will be canceled, we'll mark them as freed
- * again. */
- vmMarkPagesUsed(j->page,j->pages);
- j->type = REDIS_IOJOB_DO_SWAP;
- lockThreadedIO();
- queueIOJob(j);
- unlockThreadedIO();
- }
- } else if (j->type == REDIS_IOJOB_DO_SWAP) {
- vmpointer *vp;
-
- /* Key swapped. We can finally free some memory. */
- if (j->val->storage != REDIS_VM_SWAPPING) {
- vmpointer *vp = (vmpointer*) j->id;
- printf("storage: %d\n",vp->storage);
- printf("key->name: %s\n",(char*)j->key->ptr);
- printf("val: %p\n",(void*)j->val);
- printf("val->type: %d\n",j->val->type);
- printf("val->ptr: %s\n",(char*)j->val->ptr);
+ /* The key does not exist. Create a negative cache entry
+ * for this key. */
+ cacheSetKeyDoesNotExist(j->db,j->key);
}
- redisAssert(j->val->storage == REDIS_VM_SWAPPING);
- vp = createVmPointer(j->val->type);
- vp->page = j->page;
- vp->usedpages = j->pages;
- dictGetEntryVal(de) = vp;
- /* Fix the storage otherwise decrRefCount will attempt to
- * remove the associated I/O job */
- j->val->storage = REDIS_VM_MEMORY;
- decrRefCount(j->val);
- redisLog(REDIS_DEBUG,
- "VM: object %s swapped out at %lld (%lld pages) (threaded)",
- (unsigned char*) j->key->ptr,
- (unsigned long long) j->page, (unsigned long long) j->pages);
- server.vm_stats_swapped_objects++;
- server.vm_stats_swapouts++;
+ cacheScheduleIODelFlag(j->db,j->key,REDIS_IO_LOADINPROG);
+ handleClientsBlockedOnSwappedKey(j->db,j->key);
freeIOJob(j);
- /* Put a few more swap requests in queue if we are still
- * out of memory */
- if (trytoswap && vmCanSwapOut() &&
- zmalloc_used_memory() > server.vm_max_memory)
- {
- int more = 1;
- while(more) {
- lockThreadedIO();
- more = listLength(server.io_newjobs) <
- (unsigned) server.vm_max_threads;
- unlockThreadedIO();
- /* Don't waste CPU time if swappable objects are rare. */
- if (vmSwapOneObjectThreaded() == REDIS_ERR) {
- trytoswap = 0;
- break;
- }
- }
+ } else if (j->type == REDIS_IOJOB_SAVE) {
+ if (j->val) {
+ cacheSetKeyMayExist(j->db,j->key);
+ } else {
+ cacheSetKeyDoesNotExist(j->db,j->key);
}
+ cacheScheduleIODelFlag(j->db,j->key,REDIS_IO_SAVEINPROG);
+ freeIOJob(j);
}
processed++;
if (processed == toprocess) return;
REDIS_NOTUSED(arg);
pthread_detach(pthread_self());
+ lockThreadedIO();
while(1) {
/* Get a new job to process */
- lockThreadedIO();
if (listLength(server.io_newjobs) == 0) {
- /* No new jobs in queue, exit. */
- redisLog(REDIS_DEBUG,"Thread %ld exiting, nothing to do",
- (long) pthread_self());
- server.io_active_threads--;
- unlockThreadedIO();
- return NULL;
+ /* Wait for more work to do */
+ pthread_cond_wait(&server.io_condvar,&server.io_mutex);
+ continue;
}
+ redisLog(REDIS_DEBUG,"%ld IO jobs to process",
+ listLength(server.io_newjobs));
ln = listFirst(server.io_newjobs);
j = ln->value;
listDelNode(server.io_newjobs,ln);
/* Add the job in the processing queue */
- j->thread = pthread_self();
listAddNodeTail(server.io_processing,j);
ln = listLast(server.io_processing); /* We use ln later to remove it */
unlockThreadedIO();
- redisLog(REDIS_DEBUG,"Thread %ld got a new job (type %d): %p about key '%s'",
- (long) pthread_self(), j->type, (void*)j, (char*)j->key->ptr);
+
+ redisLog(REDIS_DEBUG,"Thread %ld: new job type %s: %p about key '%s'",
+ (long) pthread_self(),
+ (j->type == REDIS_IOJOB_LOAD) ? "load" : "save",
+ (void*)j, (char*)j->key->ptr);
/* Process the Job */
if (j->type == REDIS_IOJOB_LOAD) {
- vmpointer *vp = (vmpointer*)j->id;
- j->val = vmReadObjectFromSwap(j->page,vp->vtype);
- } else if (j->type == REDIS_IOJOB_PREPARE_SWAP) {
- j->pages = rdbSavedObjectPages(j->val);
- } else if (j->type == REDIS_IOJOB_DO_SWAP) {
- if (vmWriteObjectOnSwap(j->val,j->page) == REDIS_ERR)
- j->canceled = 1;
+ time_t expire;
+
+ j->val = dsGet(j->db,j->key,&expire);
+ if (j->val) j->expire = expire;
+ } else if (j->type == REDIS_IOJOB_SAVE) {
+ if (j->val) {
+ dsSet(j->db,j->key,j->val);
+ } else {
+ dsDel(j->db,j->key);
+ }
}
/* Done: insert the job into the processed queue */
redisLog(REDIS_DEBUG,"Thread %ld completed the job: %p (key %s)",
(long) pthread_self(), (void*)j, (char*)j->key->ptr);
+
lockThreadedIO();
listDelNode(server.io_processing,ln);
listAddNodeTail(server.io_processed,j);
- unlockThreadedIO();
/* Signal the main thread there is new stuff to process */
redisAssert(write(server.io_ready_pipe_write,"x",1) == 1);
}
- return NULL; /* never reached */
+ /* never reached, but that's the full pattern... */
+ unlockThreadedIO();
+ return NULL;
}
void spawnIOThread(void) {
server.io_active_threads++;
}
-/* We need to wait for the last thread to exit before we are able to
- * fork() in order to BGSAVE or BGREWRITEAOF. */
+/* Wait that all the pending IO Jobs are processed */
void waitEmptyIOJobsQueue(void) {
while(1) {
int io_processed_len;
lockThreadedIO();
if (listLength(server.io_newjobs) == 0 &&
- listLength(server.io_processing) == 0 &&
- server.io_active_threads == 0)
+ listLength(server.io_processing) == 0)
{
unlockThreadedIO();
return;
}
+ /* If there are new jobs we need to signal the thread to
+ * process the next one. */
+ redisLog(REDIS_DEBUG,"waitEmptyIOJobsQueue: new %d, processing %d",
+ listLength(server.io_newjobs),
+ listLength(server.io_processing));
+ /*
+ if (listLength(server.io_newjobs)) {
+ pthread_cond_signal(&server.io_condvar);
+ }
+ */
/* While waiting for empty jobs queue condition we post-process some
* finshed job, as I/O threads may be hanging trying to write against
* the io_ready_pipe_write FD but there are so much pending jobs that
}
}
+/* Process all the IO Jobs already completed by threads but still waiting
+ * processing from the main thread. */
+void processAllPendingIOJobs(void) {
+ while(1) {
+ int io_processed_len;
+
+ lockThreadedIO();
+ io_processed_len = listLength(server.io_processed);
+ unlockThreadedIO();
+ if (io_processed_len == 0) return;
+ vmThreadedIOCompletedJob(NULL,server.io_ready_pipe_read,
+ (void*)0xdeadbeef,0);
+ }
+}
+
/* This function must be called while with threaded IO locked */
void queueIOJob(iojob *j) {
redisLog(REDIS_DEBUG,"Queued IO Job %p type %d about key '%s'\n",
spawnIOThread();
}
-int vmSwapObjectThreaded(robj *key, robj *val, redisDb *db) {
+void dsCreateIOJob(int type, redisDb *db, robj *key, robj *val) {
iojob *j;
j = zmalloc(sizeof(*j));
- j->type = REDIS_IOJOB_PREPARE_SWAP;
+ j->type = type;
j->db = db;
j->key = key;
incrRefCount(key);
- j->id = j->val = val;
- incrRefCount(val);
- j->canceled = 0;
- j->thread = (pthread_t) -1;
- val->storage = REDIS_VM_SWAPPING;
+ j->val = val;
+ if (val) incrRefCount(val);
lockThreadedIO();
queueIOJob(j);
+ pthread_cond_signal(&server.io_condvar);
unlockThreadedIO();
- return REDIS_OK;
}
-/* ============ Virtual Memory - Blocking clients on missing keys =========== */
+/* ============= Disk store cache - Scheduling of IO operations =============
+ *
+ * We use a queue and an hash table to hold the state of IO operations
+ * so that's fast to lookup if there is already an IO operation in queue
+ * for a given key.
+ *
+ * There are two types of IO operations for a given key:
+ * REDIS_IO_LOAD and REDIS_IO_SAVE.
+ *
+ * The function cacheScheduleIO() function pushes the specified IO operation
+ * in the queue, but avoid adding the same key for the same operation
+ * multiple times, thanks to the associated hash table.
+ *
+ * We take a set of flags per every key, so when the scheduled IO operation
+ * gets moved from the scheduled queue to the actual IO Jobs queue that
+ * is processed by the IO thread, we flag it as IO_LOADINPROG or
+ * IO_SAVEINPROG.
+ *
+ * So for every given key we always know if there is some IO operation
+ * scheduled, or in progress, for this key.
+ *
+ * NOTE: all this is very important in order to guarantee correctness of
+ * the Disk Store Cache. Jobs are always queued here. Load jobs are
+ * queued at the head for faster execution only in the case there is not
+ * already a write operation of some kind for this job.
+ *
+ * So we have ordering, but can do exceptions when there are no already
+ * operations for a given key. Also when we need to block load a given
+ * key, for an immediate lookup operation, we can check if the key can
+ * be accessed synchronously without race conditions (no IN PROGRESS
+ * operations for this key), otherwise we blocking wait for completion. */
+
+#define REDIS_IO_LOAD 1
+#define REDIS_IO_SAVE 2
+#define REDIS_IO_LOADINPROG 4
+#define REDIS_IO_SAVEINPROG 8
+
+void cacheScheduleIOAddFlag(redisDb *db, robj *key, long flag) {
+ struct dictEntry *de = dictFind(db->io_queued,key);
+
+ if (!de) {
+ dictAdd(db->io_queued,key,(void*)flag);
+ incrRefCount(key);
+ return;
+ } else {
+ long flags = (long) dictGetEntryVal(de);
+
+ if (flags & flag) {
+ redisLog(REDIS_WARNING,"Adding the same flag again: was: %ld, addede: %ld",flags,flag);
+ redisAssert(!(flags & flag));
+ }
+ flags |= flag;
+ dictGetEntryVal(de) = (void*) flags;
+ }
+}
+
+void cacheScheduleIODelFlag(redisDb *db, robj *key, long flag) {
+ struct dictEntry *de = dictFind(db->io_queued,key);
+ long flags;
+
+ redisAssert(de != NULL);
+ flags = (long) dictGetEntryVal(de);
+ redisAssert(flags & flag);
+ flags &= ~flag;
+ if (flags == 0) {
+ dictDelete(db->io_queued,key);
+ } else {
+ dictGetEntryVal(de) = (void*) flags;
+ }
+}
+
+int cacheScheduleIOGetFlags(redisDb *db, robj *key) {
+ struct dictEntry *de = dictFind(db->io_queued,key);
+
+ return (de == NULL) ? 0 : ((long) dictGetEntryVal(de));
+}
+
+void cacheScheduleIO(redisDb *db, robj *key, int type) {
+ ioop *op;
+ long flags;
+
+ if ((flags = cacheScheduleIOGetFlags(db,key)) & type) return;
+
+ redisLog(REDIS_DEBUG,"Scheduling key %s for %s",
+ key->ptr, type == REDIS_IO_LOAD ? "loading" : "saving");
+ cacheScheduleIOAddFlag(db,key,type);
+ op = zmalloc(sizeof(*op));
+ op->type = type;
+ op->db = db;
+ op->key = key;
+ incrRefCount(key);
+ op->ctime = time(NULL);
+
+ /* Give priority to load operations if there are no save already
+ * in queue for the same key. */
+ if (type == REDIS_IO_LOAD && !(flags & REDIS_IO_SAVE)) {
+ listAddNodeHead(server.cache_io_queue, op);
+ } else {
+ /* FIXME: probably when this happens we want to at least move
+ * the write job about this queue on top, and set the creation time
+ * to a value that will force processing ASAP. */
+ listAddNodeTail(server.cache_io_queue, op);
+ }
+}
+
+void cacheCron(void) {
+ time_t now = time(NULL);
+ listNode *ln;
+ int jobs, topush = 0;
+
+ /* Sync stuff on disk, but only if we have less than 100 IO jobs */
+ lockThreadedIO();
+ jobs = listLength(server.io_newjobs);
+ unlockThreadedIO();
+
+ topush = 100-jobs;
+ if (topush < 0) topush = 0;
+ if (topush > (signed)listLength(server.cache_io_queue))
+ topush = listLength(server.cache_io_queue);
+
+ while((ln = listFirst(server.cache_io_queue)) != NULL) {
+ ioop *op = ln->value;
+
+ if (!topush) break;
+ topush--;
+
+ if (op->type == REDIS_IO_LOAD ||
+ (now - op->ctime) >= server.cache_flush_delay)
+ {
+ struct dictEntry *de;
+ robj *val;
+
+ /* Don't add a SAVE job in queue if there is already
+ * a save in progress for the same key. */
+ if (op->type == REDIS_IO_SAVE &&
+ cacheScheduleIOGetFlags(op->db,op->key) & REDIS_IO_SAVEINPROG)
+ {
+ /* Move the operation at the end of the list of there
+ * are other operations. Otherwise break, nothing to do
+ * here. */
+ if (listLength(server.cache_io_queue) > 1) {
+ listDelNode(server.cache_io_queue,ln);
+ listAddNodeTail(server.cache_io_queue,op);
+ continue;
+ } else {
+ break;
+ }
+ }
+
+ redisLog(REDIS_DEBUG,"Creating IO %s Job for key %s",
+ op->type == REDIS_IO_LOAD ? "load" : "save", op->key->ptr);
+
+ if (op->type == REDIS_IO_LOAD) {
+ dsCreateIOJob(REDIS_IOJOB_LOAD,op->db,op->key,NULL);
+ } else {
+ /* Lookup the key, in order to put the current value in the IO
+ * Job. Otherwise if the key does not exists we schedule a disk
+ * store delete operation, setting the value to NULL. */
+ de = dictFind(op->db->dict,op->key->ptr);
+ if (de) {
+ val = dictGetEntryVal(de);
+ } else {
+ /* Setting the value to NULL tells the IO thread to delete
+ * the key on disk. */
+ val = NULL;
+ }
+ dsCreateIOJob(REDIS_IOJOB_SAVE,op->db,op->key,val);
+ }
+ /* Mark the operation as in progress. */
+ cacheScheduleIODelFlag(op->db,op->key,op->type);
+ cacheScheduleIOAddFlag(op->db,op->key,
+ (op->type == REDIS_IO_LOAD) ? REDIS_IO_LOADINPROG :
+ REDIS_IO_SAVEINPROG);
+ /* Finally remove the operation from the queue.
+ * But we'll have trace of it in the hash table. */
+ listDelNode(server.cache_io_queue,ln);
+ decrRefCount(op->key);
+ zfree(op);
+ } else {
+ break; /* too early */
+ }
+ }
+
+ /* Reclaim memory from the object cache */
+ while (server.ds_enabled && zmalloc_used_memory() >
+ server.cache_max_memory)
+ {
+ if (cacheFreeOneEntry() == REDIS_ERR) break;
+ /* FIXME: also free negative cache entries here. */
+ }
+}
+
+/* ========== Disk store cache - Blocking clients on missing keys =========== */
/* This function makes the clinet 'c' waiting for the key 'key' to be loaded.
- * If there is not already a job loading the key, it is craeted.
- * The key is added to the io_keys list in the client structure, and also
+ * If the key is already in memory we don't need to block.
+ *
+ * FIXME: we should try if it's actually better to suspend the client
+ * accessing an object that is being saved, and awake it only when
+ * the saving was completed.
+ *
+ * Otherwise if the key is not in memory, we block the client and start
+ * an IO Job to load it:
+ *
+ * the key is added to the io_keys list in the client structure, and also
* in the hash table mapping swapped keys to waiting clients, that is,
* server.io_waited_keys. */
int waitForSwappedKey(redisClient *c, robj *key) {
struct dictEntry *de;
- robj *o;
list *l;
- /* If the key does not exist or is already in RAM we don't need to
- * block the client at all. */
+ /* Return ASAP if the key is in memory */
de = dictFind(c->db->dict,key->ptr);
- if (de == NULL) return 0;
- o = dictGetEntryVal(de);
- if (o->storage == REDIS_VM_MEMORY) {
- return 0;
- } else if (o->storage == REDIS_VM_SWAPPING) {
- /* We were swapping the key, undo it! */
- vmCancelThreadedIOJob(o);
- return 0;
- }
+ if (de != NULL) return 0;
- /* OK: the key is either swapped, or being loaded just now. */
+ /* Don't wait for keys we are sure are not on disk either */
+ if (!cacheKeyMayExist(c->db,key)) return 0;
/* Add the key to the list of keys this client is waiting for.
* This maps clients to keys they are waiting for. */
listAddNodeTail(l,c);
/* Are we already loading the key from disk? If not create a job */
- if (o->storage == REDIS_VM_SWAPPED) {
- iojob *j;
- vmpointer *vp = (vmpointer*)o;
-
- o->storage = REDIS_VM_LOADING;
- j = zmalloc(sizeof(*j));
- j->type = REDIS_IOJOB_LOAD;
- j->db = c->db;
- j->id = (robj*)vp;
- j->key = key;
- incrRefCount(key);
- j->page = vp->page;
- j->val = NULL;
- j->canceled = 0;
- j->thread = (pthread_t) -1;
- lockThreadedIO();
- queueIOJob(j);
- unlockThreadedIO();
- }
+ if (de == NULL)
+ cacheScheduleIO(c->db,key,REDIS_IO_LOAD);
return 1;
}
if (listLength(c->io_keys)) {
c->flags |= REDIS_IO_WAIT;
aeDeleteFileEvent(server.el,c->fd,AE_READABLE);
- server.vm_blocked_clients++;
+ server.cache_blocked_clients++;
return 1;
} else {
return 0;
projects / redis.git / blobdiff