On 2012年07月26日 15:55, Liu Yuan wrote:
> On 07/26/2012 03:17 PM, levin li wrote:
>> +static inline int cache_is_flushing(struct object_cache *cache)
>> +{
>> + return cache->in_flush;
>> +}
>> +
>
> better renamed as cache_in_flush()
>
>> +static inline int entry_is_reclaiming(struct object_cache_entry *entry)
>> +{
>> + int flags = uatomic_read(&entry->flags);
>> + if (flags & ENTRY_RECLAIM_BIT)
>> + return 1;
>> + return 0;
>> +}
>> +
>
> ditto, entry_in_flush()
>
>> +static inline int entry_is_dirty(struct object_cache_entry *entry)
>> +{
>> + return !!entry->bmap;
>> +}
>> +
>> +static inline void mark_entry_reclaiming(struct object_cache_entry *entry)
>> +{
>> + int flags = uatomic_read(&entry->flags);
>> + flags |= ENTRY_RECLAIM_BIT;
>> + uatomic_set(&entry->flags, flags);
>> +}
>> +
>
> I think mark_entry_reclaim() would be simpler.
>
>> +static int check_cache_status(struct object_cache *oc,
>> + struct object_cache_entry *entry)
>> +{
>> + if (cache_is_flushing(oc)) {
>> + dprintf("cache %" PRIx32 " is flushing, don't reclaim it.\n",
>> + oc->vid);
>> + return SD_RES_CACHE_FLUSHING;
>> + }
>> +
>> + /* If entry is being accessed, we don't reclaim it */
>> + if (uatomic_read(&entry->refcnt) > 0) {
>> + dprintf("cache object %" PRIx32 "(%08" PRIx32 ") "
>> + "can't be reclaimed, refcnt: %d\n",
>> + oc->vid, entry->idx, uatomic_read(&entry->refcnt));
>> + return SD_RES_CACHE_REFERENCING;
>> + }
>
> use a variable for uatomic_read(&entry->refcnt), we should avoid use
> uatomic_read(&entry->refcnt in dprintf().
>
>> +
>> + return SD_RES_SUCCESS;
>> +}
>> +
>> +static int reclaim_object(struct object_cache_entry *entry)
>> +{
>> + struct object_cache *oc = entry->oc;
>> + uint32_t idx = entry->idx;
>> + int ret = SD_RES_SUCCESS;
>> +
>> + pthread_rwlock_wrlock(&oc->lock);
>> + dprintf("reclaiming /%06"PRIx32"/%08"PRIx32", cache_size: %ld\n",
>> + oc->vid, idx, uatomic_read(&sys_cache.cache_size));
>> +
>> + ret = check_cache_status(oc, entry);
>> + if (ret != SD_RES_SUCCESS)
>> + goto out;
>> +
>> + if (entry_is_dirty(entry)) {
>> + uint64_t bmap = entry->bmap;
>> + int create = entry->flags & ENTRY_CREATE_BIT;
>> +
>> + entry->bmap = 0;
>> + del_from_dirty_tree_and_list(entry, &oc->dirty_tree);
>> + pthread_rwlock_unlock(&oc->lock);
>> +
>> + ret = push_cache_object(oc->vid, idx, bmap, create);
>> +
>> + pthread_rwlock_wrlock(&oc->lock);
>> + if (ret == SD_RES_SUCCESS) {
>> + entry->flags &= ~ENTRY_CREATE_BIT;
>> + /* dirty again */
>> + if (entry_is_dirty(entry)) {
>> + dprintf("object cache is dirty again %06" PRIx32 "\n", idx);
>> + ret = SD_RES_CACHE_REFERENCING;
>> + goto out;
>> + }
>> + } else {
>> + /* still dirty */
>> + entry->bmap |= bmap;
>> + ret = SD_RES_CACHE_REFERENCING;
>> + goto out;
>> + }
>> +
>> + /* Now we get lock again, check cache status again */
>> + ret = check_cache_status(oc, entry);
>> + if (ret != SD_RES_SUCCESS)
>> + goto out;
>> + }
>> +
>> + mark_entry_reclaiming(entry);
>> +
>> + ret = remove_cache_object(oc, idx);
>> + if (ret == SD_RES_SUCCESS)
>> + del_from_object_tree_and_list(entry, &oc->object_tree);
>> +out:
>> + pthread_rwlock_unlock(&oc->lock);
>> + return ret;
>> +}
>> +
>> +static void reclaim_work(struct work *work)
>> +{
>> + struct object_cache_entry *entry, *n;
>> + int ret;
>> +
>> + if (node_in_recovery())
>> + return;
>> +
>> + list_for_each_entry_revert_safe_rcu(entry, n,
>> + &sys_cache.cache_lru_list, lru_list) {
>> + /* Reclaim cache to 80% of max size */
>> + if (uatomic_read(&sys_cache.cache_size) <=
>> + sys->cache_size * 8 / 10)
>> + break;
>> +
>> + ret = reclaim_object(entry);
>> + if (ret == SD_RES_CACHE_FLUSHING)
>> + /* If cache is flushing, stop reclaiming. */
>> + break;
>> +
>> + if (ret == SD_RES_SUCCESS) {
>> + unsigned data_length;
>> + if (idx_has_vdi_bit(entry->idx))
>> + data_length = SD_INODE_SIZE;
>> + else
>> + data_length = SD_DATA_OBJ_SIZE;
>> +
>> + uatomic_sub(&sys_cache.cache_size, data_length);
>> + free(entry);
>> + }
>> + }
>> +
>> + dprintf("cache reclaim complete\n");
>> +}
>> +
>> +static void reclaim_done(struct work *work)
>> +{
>> + uatomic_set(&sys_cache.reclaiming, 0);
>> + free(work);
>> +}
>> +
>> static struct object_cache_entry *
>> dirty_tree_insert(struct object_cache *oc, uint32_t idx,
>> uint64_t bmap, int create)
>> @@ -183,6 +556,8 @@ dirty_tree_insert(struct object_cache *oc, uint32_t idx,
>> else {
>> /* already has this entry, merge bmap */
>> entry->bmap |= bmap;
>> + if (create)
>> + entry->flags |= ENTRY_CREATE_BIT;
>> return entry;
>> }
>> }
>> @@ -192,7 +567,8 @@ dirty_tree_insert(struct object_cache *oc, uint32_t idx,
>> return NULL;
>>
>> entry->bmap |= bmap;
>> - entry->flags |= ENTRY_CREATE_BIT;
>> + if (create)
>> + entry->flags |= ENTRY_CREATE_BIT;
>> rb_link_node(&entry->dirty_node, parent, p);
>> rb_insert_color(&entry->dirty_node, &oc->dirty_tree);
>> list_add(&entry->list, &oc->dirty_list);
>> @@ -200,26 +576,6 @@ dirty_tree_insert(struct object_cache *oc, uint32_t idx,
>> return entry;
>> }
>>
>> -static struct object_cache_entry *dirty_tree_search(struct rb_root *root,
>> - uint32_t idx)
>> -{
>> - struct rb_node *n = root->rb_node;
>> - struct object_cache_entry *t;
>> -
>> - while (n) {
>> - t = rb_entry(n, struct object_cache_entry, dirty_node);
>> -
>> - if (idx < t->idx)
>> - n = n->rb_left;
>> - else if (idx > t->idx)
>> - n = n->rb_right;
>> - else
>> - return t; /* found it */
>> - }
>> -
>> - return NULL;
>> -}
>> -
>> static int create_dir_for(uint32_t vid)
>> {
>> int ret = 0;
>> @@ -257,6 +613,7 @@ not_found:
>> if (create) {
>> cache = xzalloc(sizeof(*cache));
>> cache->vid = vid;
>> + cache->object_tree = RB_ROOT;
>> create_dir_for(vid);
>>
>> cache->dirty_tree = RB_ROOT;
>> @@ -271,14 +628,6 @@ out:
>> return cache;
>> }
>>
>> -static inline void
>> -del_from_dirty_tree_and_list(struct object_cache_entry *entry,
>> - struct rb_root *dirty_tree)
>> -{
>> - rb_erase(&entry->dirty_node, dirty_tree);
>> - list_del(&entry->list);
>> -}
>> -
>> /* Caller should hold the oc->lock */
>> static inline void
>> add_to_dirty_tree_and_list(struct object_cache *oc, uint32_t idx,
>> @@ -289,6 +638,9 @@ add_to_dirty_tree_and_list(struct object_cache *oc, uint32_t idx,
>> if (!entry)
>> panic("Can not find object entry %" PRIx32 "\n", idx);
>>
>> + if (cache_in_reclaim(0))
>> + return;
>> +
>> /* If cache isn't in reclaiming, move it
>> * to the head of lru list */
>> cds_list_del_rcu(&entry->lru_list);
>> @@ -312,15 +664,18 @@ static void add_to_object_cache(struct object_cache *oc, uint32_t idx)
>> uint32_t data_length;
>>
>> if (idx_has_vdi_bit(idx))
>> - data_length = SD_INODE_SIZE / 1024;
>> + data_length = SD_INODE_SIZE;
>> else
>> - data_length = SD_DATA_OBJ_SIZE / 1024;
>> + data_length = SD_DATA_OBJ_SIZE;
>>
>> entry = xzalloc(sizeof(*entry));
>> entry->oc = oc;
>> entry->idx = idx;
>> CDS_INIT_LIST_HEAD(&entry->lru_list);
>>
>> + dprintf("cache object for vdi %" PRIx32 ", idx %08" PRIx32 "added\n",
>> + oc->vid, idx);
>> +
>> pthread_rwlock_wrlock(&oc->lock);
>> old = object_cache_insert(&oc->object_tree, entry);
>> if (!old) {
>> @@ -331,20 +686,51 @@ static void add_to_object_cache(struct object_cache *oc, uint32_t idx)
>> entry = old;
>> }
>> pthread_rwlock_unlock(&oc->lock);
>> +
>> + dprintf("sys_cache.cache_size %" PRIx64 ", sys->cache_size %" PRIx64 "\n",
>> + uatomic_read(&sys_cache.cache_size), sys->cache_size);
>> + if (sys->cache_size &&
>> + uatomic_read(&sys_cache.cache_size) > sys->cache_size &&
>> + !cache_in_reclaim(1)) {
>> + struct work *work = xzalloc(sizeof(struct work));
>> + work->fn = reclaim_work;
>> + work->done = reclaim_done;
>> + queue_work(sys->reclaim_wqueue, work);
>> + }
>> +}
>> +
>> +static inline struct object_cache_entry *
>> +find_cache_entry(struct object_cache *oc, uint32_t idx)
>> +{
>> + struct object_cache_entry *entry;
>> +
>> + entry = object_tree_search(&oc->object_tree, idx);
>> + if (!entry || entry_is_reclaiming(entry))
>> + return NULL;
>> +
>> + return entry;
>> }
>>
>> static int object_cache_lookup(struct object_cache *oc, uint32_t idx,
>> int create)
>> {
>> struct strbuf buf;
>> - int fd, ret = 0, flags = def_open_flags;
>> + int fd, ret = SD_RES_SUCCESS, flags = def_open_flags;
>> + unsigned data_length;
>> +
>> + if (!create) {
>> + pthread_rwlock_wrlock(&oc->lock);
>> + if (!find_cache_entry(oc, idx))
>> + ret = SD_RES_NO_CACHE;
>> + pthread_rwlock_unlock(&oc->lock);
>> + return ret;
>> + }
>>
>> strbuf_init(&buf, PATH_MAX);
>> strbuf_addstr(&buf, cache_dir);
>> strbuf_addf(&buf, "/%06"PRIx32"/%08"PRIx32, oc->vid, idx);
>>
>> - if (create)
>> - flags |= O_CREAT | O_TRUNC;
>> + flags |= O_CREAT | O_TRUNC;
>>
>> fd = open(buf.buf, flags, def_fmode);
>> if (fd < 0) {
>> @@ -352,26 +738,22 @@ static int object_cache_lookup(struct object_cache *oc, uint32_t idx,
>> goto out;
>> }
>>
>> - if (create) {
>> - unsigned data_length;
>> -
>> - if (idx_has_vdi_bit(idx))
>> - data_length = SD_INODE_SIZE;
>> - else
>> - data_length = SD_DATA_OBJ_SIZE;
>> + if (idx_has_vdi_bit(idx))
>> + data_length = SD_INODE_SIZE;
>> + else
>> + data_length = SD_DATA_OBJ_SIZE;
>>
>> - ret = prealloc(fd, data_length);
>> - if (ret != SD_RES_SUCCESS)
>> - ret = -1;
>> - else {
>> - uint64_t bmap = UINT64_MAX;
>> + ret = prealloc(fd, data_length);
>> + if (ret != SD_RES_SUCCESS)
>> + ret = -1;
>> + else {
>> + uint64_t bmap = UINT64_MAX;
>>
>> - add_to_object_cache(oc, idx);
>> + add_to_object_cache(oc, idx);
>>
>> - pthread_rwlock_wrlock(&oc->lock);
>> - add_to_dirty_tree_and_list(oc, idx, bmap, 1);
>> - pthread_rwlock_unlock(&oc->lock);
>> - }
>> + pthread_rwlock_wrlock(&oc->lock);
>> + add_to_dirty_tree_and_list(oc, idx, bmap, 1);
>> + pthread_rwlock_unlock(&oc->lock);
>> }
>> close(fd);
>> out:
>> @@ -379,97 +761,6 @@ out:
>> return ret;
>> }
>>
>> -static int write_cache_object(uint32_t vid, uint32_t idx, void *buf,
>> - size_t count, off_t offset)
>> -{
>> - size_t size;
>> - int fd, flags = def_open_flags, ret = SD_RES_SUCCESS;
>> - struct strbuf p;
>> -
>> - strbuf_init(&p, PATH_MAX);
>> - strbuf_addstr(&p, cache_dir);
>> - strbuf_addf(&p, "/%06"PRIx32"/%08"PRIx32, vid, idx);
>> -
>> - if (sys->use_directio && !idx_has_vdi_bit(idx))
>> - flags |= O_DIRECT;
>> -
>> - fd = open(p.buf, flags, def_fmode);
>> - if (fd < 0) {
>> - eprintf("%m\n");
>> - ret = SD_RES_EIO;
>> - goto out;
>> - }
>> -
>> - if (flock(fd, LOCK_EX) < 0) {
>> - ret = SD_RES_EIO;
>> - eprintf("%m\n");
>> - goto out_close;
>> - }
>> - size = xpwrite(fd, buf, count, offset);
>> - if (flock(fd, LOCK_UN) < 0) {
>> - ret = SD_RES_EIO;
>> - eprintf("%m\n");
>> - goto out_close;
>> - }
>> -
>> - if (size != count) {
>> - eprintf("size %zu, count:%zu, offset %jd %m\n",
>> - size, count, (intmax_t)offset);
>> - ret = SD_RES_EIO;
>> - }
>> -out_close:
>> - close(fd);
>> -out:
>> - strbuf_release(&p);
>> - return ret;
>> -}
>> -
>> -static int read_cache_object(uint32_t vid, uint32_t idx, void *buf,
>> - size_t count, off_t offset)
>> -{
>> - size_t size;
>> - int fd, flags = def_open_flags, ret = SD_RES_SUCCESS;
>> - struct strbuf p;
>> -
>> - strbuf_init(&p, PATH_MAX);
>> - strbuf_addstr(&p, cache_dir);
>> - strbuf_addf(&p, "/%06"PRIx32"/%08"PRIx32, vid, idx);
>> -
>> - if (sys->use_directio && !idx_has_vdi_bit(idx))
>> - flags |= O_DIRECT;
>> -
>> - fd = open(p.buf, flags, def_fmode);
>> - if (fd < 0) {
>> - eprintf("%m\n");
>> - ret = SD_RES_EIO;
>> - goto out;
>> - }
>> -
>> - if (flock(fd, LOCK_SH) < 0) {
>> - ret = SD_RES_EIO;
>> - eprintf("%m\n");
>> - goto out_close;
>> - }
>> - size = xpread(fd, buf, count, offset);
>> - if (flock(fd, LOCK_UN) < 0) {
>> - ret = SD_RES_EIO;
>> - eprintf("%m\n");
>> - goto out_close;
>> - }
>> -
>> - if (size != count) {
>> - eprintf("size %zu, count:%zu, offset %jd %m\n",
>> - size, count, (intmax_t)offset);
>> - ret = SD_RES_EIO;
>> - }
>> -
>> -out_close:
>> - close(fd);
>> -out:
>> - strbuf_release(&p);
>> - return ret;
>> -}
>> -
>> static int create_cache_object(struct object_cache *oc, uint32_t idx,
>> void *buffer, size_t buf_size)
>> {
>> @@ -558,75 +849,6 @@ out:
>> return ret;
>> }
>>
>> -static uint64_t idx_to_oid(uint32_t vid, uint32_t idx)
>> -{
>> - if (idx_has_vdi_bit(idx))
>> - return vid_to_vdi_oid(vid);
>> - else
>> - return vid_to_data_oid(vid, idx);
>> -}
>> -
>> -static int push_cache_object(uint32_t vid, uint32_t idx, uint64_t bmap,
>> - int create)
>> -{
>> - struct sd_req hdr;
>> - void *buf;
>> - off_t offset;
>> - unsigned data_length;
>> - int ret = SD_RES_NO_MEM;
>> - uint64_t oid = idx_to_oid(vid, idx);
>> - int first_bit, last_bit;
>> -
>> - dprintf("%"PRIx64", create %d\n", oid, create);
>> -
>> - if (!bmap) {
>> - dprintf("WARN: nothing to flush\n");
>> - return SD_RES_SUCCESS;
>> - }
>> -
>> - first_bit = ffsll(bmap) - 1;
>> - last_bit = fls64(bmap) - 1;
>> -
>> - dprintf("bmap:0x%"PRIx64", first_bit:%d, last_bit:%d\n",
>> - bmap, first_bit, last_bit);
>> - offset = first_bit * CACHE_BLOCK_SIZE;
>> - data_length = (last_bit - first_bit + 1) * CACHE_BLOCK_SIZE;
>> -
>> - /*
>> - * CACHE_BLOCK_SIZE may not be divisible by SD_INODE_SIZE,
>> - * so (offset + data_length) could larger than SD_INODE_SIZE
>> - */
>> - if (is_vdi_obj(oid) && (offset + data_length) > SD_INODE_SIZE)
>> - data_length = SD_INODE_SIZE - offset;
>> -
>> - buf = valloc(data_length);
>> - if (buf == NULL) {
>> - eprintf("failed to allocate memory\n");
>> - goto out;
>> - }
>> -
>> - ret = read_cache_object(vid, idx, buf, data_length, offset);
>> - if (ret != SD_RES_SUCCESS)
>> - goto out;
>> -
>> - if (create)
>> - sd_init_req(&hdr, SD_OP_CREATE_AND_WRITE_OBJ);
>> - else
>> - sd_init_req(&hdr, SD_OP_WRITE_OBJ);
>> - hdr.flags = SD_FLAG_CMD_WRITE;
>> - hdr.data_length = data_length;
>> - hdr.obj.oid = oid;
>> - hdr.obj.offset = offset;
>> -
>> - ret = exec_local_req(&hdr, buf);
>> - if (ret != SD_RES_SUCCESS)
>> - eprintf("failed to push object %x\n", ret);
>> -
>> -out:
>> - free(buf);
>> - return ret;
>> -}
>> -
>> /* Push back all the dirty objects to sheep cluster storage */
>> static int object_cache_push(struct object_cache *oc)
>> {
>> @@ -647,20 +869,23 @@ static int object_cache_push(struct object_cache *oc)
>> pthread_rwlock_rdlock(&oc->lock);
>> bmap = entry->bmap;
>> create = entry->flags & ENTRY_CREATE_BIT;
>> + entry->bmap = 0;
>> pthread_rwlock_unlock(&oc->lock);
>>
>> ret = push_cache_object(oc->vid, entry->idx, bmap, create);
>> - if (ret != SD_RES_SUCCESS)
>> - goto push_failed;
>>
>> pthread_rwlock_wrlock(&oc->lock);
>> + if (ret != SD_RES_SUCCESS) {
>> + entry->bmap |= bmap;
>> + goto push_failed;
>> + }
>> + entry->flags &= ~ENTRY_CREATE_BIT;
>> del_from_dirty_tree_and_list(entry, &oc->dirty_tree);
>> pthread_rwlock_unlock(&oc->lock);
>> }
>> return ret;
>>
>> push_failed:
>> - pthread_rwlock_wrlock(&oc->lock);
>> list_splice_init(&inactive_dirty_list, &oc->dirty_list);
>> pthread_rwlock_unlock(&oc->lock);
>>
>> @@ -677,10 +902,10 @@ int object_is_cached(uint64_t oid)
>> if (!cache)
>> return 0;
>>
>> - if (object_cache_lookup(cache, idx, 0) < 0)
>> - return 0;
>> + if (object_cache_lookup(cache, idx, 0) == SD_RES_SUCCESS)
>> + return 1;
>> else
>> - return 1; /* found it */
>> + return 0;
>> }
>>
>> void object_cache_delete(uint32_t vid)
>> @@ -712,6 +937,44 @@ void object_cache_delete(uint32_t vid)
>>
>> }
>>
>> +static void object_cache_flush_begin(struct object_cache *oc)
>> +{
>> + pthread_rwlock_wrlock(&oc->lock);
>> + oc->in_flush = 1;
>> + pthread_rwlock_unlock(&oc->lock);
>> +}
>> +
>> +static void object_cache_flush_end(struct object_cache *oc)
>> +{
>> + pthread_rwlock_wrlock(&oc->lock);
>> + oc->in_flush = 0;
>> + pthread_rwlock_unlock(&oc->lock);
>> +}
>> +
>
> I think we can use uatomic_cmpchg() for oc->in_flush, instead of mutex
> lock.Also, as I have mentioned, if these two helpers only operate on
> oc->in_flush, we'd better fold them into the caller to code the logic
> more explicit.
>
> Thanks,
> Yuan
>
The lock is necessary here, atomic can only guarantee the data is correct,
but not supply a function of barrier, we must make sure that when a cached
object is preparing to reclaim, the flush work should wait until the preparing
work finished, firstly I also didn't use the rwlock but just use atomic to
set this variable, but there's indeed problem causing VM error.
'begin/end' make it easy to understand the behavior, if you have a better
name, suggest one, I don't mind to merge these two helper functions.
thanks,
levin
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