glusterfs: Use gcc builtin ATOMIC operator to increase/decreate refcount.

Problem: In glusterfs code base we call mutex_lock/unlock to take
         reference/dereference for a object.Sometime it could be
         reason for lock contention also.

Solution: There is no need to use mutex to increase/decrease ref
          counter, instead of using mutex use gcc builtin ATOMIC
          operation.

Test:   I have not observed yet how much performance gain after apply
        this patch specific to glusterfs but i have tested same
        with below small program(mutex and atomic both) and
        get good difference.

static int numOuterLoops;
static void *
threadFunc(void *arg)
{
    int j;

    for (j = 0; j < numOuterLoops; j++) {
            __atomic_add_fetch (&glob, 1,__ATOMIC_ACQ_REL);
    }
    return NULL;
}

int
main(int argc, char *argv[])
{
    int opt, s, j;
    int numThreads;
    pthread_t *thread;
    int verbose;
    int64_t n = 0;

    if (argc < 2 ) {
     printf(" Please provide 2 args Num of threads && Outer Loop\n");
     exit (-1);
    }
    numThreads = atoi(argv[1]);
    numOuterLoops = atoi (argv[2]);

    if (1) {
        printf("\tthreads: %d; outer loops: %d;\n",
                numThreads, numOuterLoops);
    }

    thread = calloc(numThreads, sizeof(pthread_t));
    if (thread == NULL) {
        printf ("calloc error so exit\n");
        exit (-1);
    }

    __atomic_store (&glob, &n, __ATOMIC_RELEASE);
    for (j = 0; j < numThreads; j++) {
        s = pthread_create(&thread[j], NULL, threadFunc, NULL);
        if (s != 0) {
            printf ("pthread_create failed so exit\n");
            exit (-1);
        }
    }

    for (j = 0; j < numThreads; j++) {
        s = pthread_join(thread[j], NULL);
        if (s != 0) {
            printf ("pthread_join failed so exit\n");
            exit (-1);
        }
    }
    printf("glob value is %ld\n",__atomic_load_n (&glob,__ATOMIC_RELAXED));

    exit(0);
}

   time ./thr_count 800 800000
   threads: 800; outer loops: 800000;
   glob value is 640000000

real	1m10.288s
user	0m57.269s
sys	3m31.565s

time ./thr_count_atomic 800 800000
     threads: 800; outer loops: 800000;
glob value is 640000000

real	0m20.313s
user	1m20.558s
sys	0m0.028

Change-Id: Ie5030a52ea264875e002e108dd4b207b15ab7cc7
Signed-off-by: Mohit Agrawal <moagrawa@redhat.com>

9 files changed, 35 insertions, 162 deletions

diff --git a/libglusterfs/src/dict.c b/libglusterfs/src/dict.c
index a47c8529709..d0be267d2ee 100644
--- a/libglusterfs/src/dict.c
+++ b/libglusterfs/src/dict.c
@@ -579,8 +579,8 @@ dict_destroy (dict_t *this)
         data_pair_t *pair = this->members_list;
         data_pair_t *prev = this->members_list;
         glusterfs_ctx_t *ctx = NULL;
-        uint32_t total_pairs = 0;
         uint64_t current_max = 0;
+        uint32_t total_pairs = 0;
 
         LOCK_DESTROY (&this->lock);
 
@@ -629,7 +629,7 @@ dict_destroy (dict_t *this)
 void
 dict_unref (dict_t *this)
 {
-        int32_t ref;
+        uint64_t ref = 0;
 
         if (!this) {
                 gf_msg_callingfn ("dict", GF_LOG_WARNING, EINVAL,
@@ -637,12 +637,7 @@ dict_unref (dict_t *this)
                 return;
         }
 
-        LOCK (&this->lock);
-
-        this->refcount--;
-        ref = this->refcount;
-
-        UNLOCK (&this->lock);
+        ref = GF_ATOMIC_DEC (this->refcount);
 
         if (!ref)
                 dict_destroy (this);
@@ -657,12 +652,7 @@ dict_ref (dict_t *this)
                 return NULL;
         }
 
-        LOCK (&this->lock);
-
-        this->refcount++;
-
-        UNLOCK (&this->lock);
-
+        GF_ATOMIC_INC (this->refcount);
         return this;
 }
 
@@ -678,12 +668,7 @@ data_unref (data_t *this)
                 return;
         }
 
-        LOCK (&this->lock);
-
-        this->refcount--;
-        ref = this->refcount;
-
-        UNLOCK (&this->lock);
+        ref = GF_ATOMIC_DEC (this->refcount);
 
         if (!ref)
                 data_destroy (this);
@@ -698,11 +683,7 @@ data_ref (data_t *this)
                 return NULL;
         }
 
-        LOCK (&this->lock);
-
-        this->refcount++;
-
-        UNLOCK (&this->lock);
+        GF_ATOMIC_INC (this->refcount);
 
         return this;
 }
diff --git a/libglusterfs/src/dict.h b/libglusterfs/src/dict.h
index 713da61d4ce..48c6f242723 100644
--- a/libglusterfs/src/dict.h
+++ b/libglusterfs/src/dict.h
@@ -67,7 +67,7 @@ struct _data {
         unsigned char  is_const:1;
         int32_t        len;
         char          *data;
-        int32_t        refcount;
+        gf_atomic_t    refcount;
         gf_lock_t      lock;
 };
 
@@ -84,7 +84,7 @@ struct _dict {
         unsigned char   is_static:1;
         int32_t         hash_size;
         int32_t         count;
-        int32_t         refcount;
+        gf_atomic_t     refcount;
         data_pair_t   **members;
         data_pair_t    *members_list;
         char           *extra_free;
@@ -93,7 +93,7 @@ struct _dict {
         data_pair_t    *members_internal;
         data_pair_t     free_pair;
         gf_boolean_t    free_pair_in_use;
-        uint32_t        max_count;
+        uint64_t        max_count;
 };
 
 typedef gf_boolean_t (*dict_match_t) (dict_t *d, char *k, data_t *v,
diff --git a/libglusterfs/src/event-epoll.c b/libglusterfs/src/event-epoll.c
index 7fc53ffeaf6..45f724ab055 100644
--- a/libglusterfs/src/event-epoll.c
+++ b/libglusterfs/src/event-epoll.c
@@ -32,7 +32,7 @@ struct event_slot_epoll {
 	int fd;
 	int events;
 	int gen;
-	int ref;
+	gf_atomic_t ref;
 	int do_close;
 	int in_handler;
         int handled_error;
@@ -197,12 +197,7 @@ event_slot_get (struct event_pool *event_pool, int idx)
 		return NULL;
 
 	slot = &table[offset];
-
-	LOCK (&slot->lock);
-	{
-		slot->ref++;
-	}
-	UNLOCK (&slot->lock);
+        GF_ATOMIC_INC (slot->ref);
 
 	return slot;
 }
@@ -216,9 +211,10 @@ event_slot_unref (struct event_pool *event_pool, struct event_slot_epoll *slot,
 	int fd = -1;
 	int do_close = 0;
 
+        ref = GF_ATOMIC_DEC (slot->ref);
+
 	LOCK (&slot->lock);
 	{
-		ref = --slot->ref;
 		fd = slot->fd;
 		do_close = slot->do_close;
 	}
diff --git a/libglusterfs/src/fd-lk.c b/libglusterfs/src/fd-lk.c
index 358cf3b616a..e516f64bff6 100644
--- a/libglusterfs/src/fd-lk.c
+++ b/libglusterfs/src/fd-lk.c
@@ -65,15 +65,11 @@ fd_lk_ctx_unref (fd_lk_ctx_t *lk_ctx)
 
         GF_VALIDATE_OR_GOTO ("fd-lk", lk_ctx, err);
 
-        LOCK (&lk_ctx->lock);
-        {
-                ref = --lk_ctx->ref;
-                if (ref < 0)
-                        GF_ASSERT (!ref);
-                if (ref == 0)
-                        _fd_lk_destroy_lock_list (lk_ctx);
-        }
-        UNLOCK (&lk_ctx->lock);
+        ref = GF_ATOMIC_DEC (lk_ctx->ref);
+        if (ref < 0)
+                GF_ASSERT (!ref);
+        if (ref == 0)
+                _fd_lk_destroy_lock_list (lk_ctx);
 
         if (ref == 0) {
                 LOCK_DESTROY (&lk_ctx->lock);
@@ -86,58 +82,17 @@ err:
 }
 
 fd_lk_ctx_t *
-_fd_lk_ctx_ref (fd_lk_ctx_t *lk_ctx)
-{
-        if (!lk_ctx) {
-                gf_msg_callingfn ("fd-lk", GF_LOG_WARNING, EINVAL,
-                                  LG_MSG_INVALID_ARG, "invalid argument");
-                return NULL;
-        }
-
-        ++lk_ctx->ref;
-
-        return lk_ctx;
-}
-
-fd_lk_ctx_t *
 fd_lk_ctx_ref (fd_lk_ctx_t *lk_ctx)
 {
-        fd_lk_ctx_t *new_lk_ctx = NULL;
-
         if (!lk_ctx) {
                 gf_msg_callingfn ("fd-lk", GF_LOG_WARNING, EINVAL,
                                   LG_MSG_INVALID_ARG, "invalid argument");
                 return NULL;
         }
 
-        LOCK (&lk_ctx->lock);
-        {
-                new_lk_ctx = _fd_lk_ctx_ref (lk_ctx);
-        }
-        UNLOCK (&lk_ctx->lock);
-
-        return new_lk_ctx;
-}
-
-fd_lk_ctx_t *
-fd_lk_ctx_try_ref (fd_lk_ctx_t *lk_ctx)
-{
-        int         ret         = -1;
-        fd_lk_ctx_t *new_lk_ctx = NULL;
-
-        if (!lk_ctx) {
-                goto out;
-        }
-
-        ret = TRY_LOCK (&lk_ctx->lock);
-        if (ret)
-                goto out;
+        GF_ATOMIC_INC (lk_ctx->ref);
 
-        new_lk_ctx = _fd_lk_ctx_ref (lk_ctx);
-        UNLOCK (&lk_ctx->lock);
-
-out:
-        return new_lk_ctx;
+        return lk_ctx;
 }
 
 fd_lk_ctx_t *
diff --git a/libglusterfs/src/fd-lk.h b/libglusterfs/src/fd-lk.h
index 51f62991681..11d864dc207 100644
--- a/libglusterfs/src/fd-lk.h
+++ b/libglusterfs/src/fd-lk.h
@@ -30,7 +30,7 @@ struct _fd;
 
 struct fd_lk_ctx {
         struct list_head lk_list;
-        int   ref;
+        gf_atomic_t ref;
         gf_lock_t lock;
 };
 typedef struct fd_lk_ctx fd_lk_ctx_t;
@@ -45,16 +45,11 @@ struct fd_lk_ctx_node {
 };
 typedef struct fd_lk_ctx_node fd_lk_ctx_node_t;
 
-fd_lk_ctx_t *
-_fd_lk_ctx_ref (fd_lk_ctx_t *lk_ctx);
 
 fd_lk_ctx_t *
 fd_lk_ctx_ref (fd_lk_ctx_t *lk_ctx);
 
 fd_lk_ctx_t *
-fd_lk_ctx_try_ref (fd_lk_ctx_t *lk_ctx);
-
-fd_lk_ctx_t *
 fd_lk_ctx_create (void);
 
 int
diff --git a/libglusterfs/src/fd.c b/libglusterfs/src/fd.c
index a8a88b0f96f..c6b1a4de611 100644
--- a/libglusterfs/src/fd.c
+++ b/libglusterfs/src/fd.c
@@ -435,7 +435,7 @@ gf_fd_fdptr_get (fdtable_t *fdtable, int64_t fd)
 fd_t *
 __fd_ref (fd_t *fd)
 {
-        ++fd->refcount;
+        GF_ATOMIC_INC (fd->refcount);
 
         return fd;
 }
@@ -444,28 +444,13 @@ __fd_ref (fd_t *fd)
 fd_t *
 fd_ref (fd_t *fd)
 {
-        fd_t *refed_fd = NULL;
-
         if (!fd) {
                 gf_msg_callingfn ("fd", GF_LOG_ERROR, EINVAL,
                                   LG_MSG_INVALID_ARG, "null fd");
                 return NULL;
         }
 
-        LOCK (&fd->inode->lock);
-        refed_fd = __fd_ref (fd);
-        UNLOCK (&fd->inode->lock);
-
-        return refed_fd;
-}
-
-
-fd_t *
-__fd_unref (fd_t *fd)
-{
-        GF_ASSERT (fd->refcount);
-
-        --fd->refcount;
+        GF_ATOMIC_INC (fd->refcount);
 
         return fd;
 }
@@ -551,8 +536,7 @@ fd_unref (fd_t *fd)
 
         LOCK (&fd->inode->lock);
         {
-                __fd_unref (fd);
-                refcount = fd->refcount;
+                refcount = GF_ATOMIC_DEC (fd->refcount);
                 if (refcount == 0) {
                         if (!list_empty (&fd->inode_list)) {
                                 list_del_init (&fd->inode_list);
@@ -1186,7 +1170,7 @@ fdentry_dump_to_dict (fdentry_t *fdentry, char *prefix, dict_t *dict,
 
                 memset (key, 0, sizeof (key));
                 snprintf (key, sizeof (key), "%s.refcount", prefix);
-                ret = dict_set_int32 (dict, key, fdentry->fd->refcount);
+                ret = dict_set_int32 (dict, key, GF_ATOMIC_GET (fdentry->fd->refcount));
                 if (ret)
                         return;
 
diff --git a/libglusterfs/src/fd.h b/libglusterfs/src/fd.h
index 3b4acf762ae..3f68b1c4997 100644
--- a/libglusterfs/src/fd.h
+++ b/libglusterfs/src/fd.h
@@ -40,7 +40,7 @@ struct _fd_ctx {
 struct _fd {
         uint64_t          pid;
 	int32_t           flags;
-        int32_t           refcount;
+        gf_atomic_t       refcount;
         struct list_head  inode_list;
         struct _inode    *inode;
         gf_lock_t         lock; /* used ONLY for manipulating
diff --git a/libglusterfs/src/iobuf.c b/libglusterfs/src/iobuf.c
index 76584fc9cde..d4f0d89c338 100644
--- a/libglusterfs/src/iobuf.c
+++ b/libglusterfs/src/iobuf.c
@@ -126,7 +126,7 @@ __iobuf_arena_destroy_iobufs (struct iobuf_arena *iobuf_arena)
 
         iobuf = iobuf_arena->iobufs;
         for (i = 0; i < iobuf_cnt; i++) {
-                GF_ASSERT (iobuf->ref == 0);
+                GF_ASSERT (GF_ATOMIC_GET(iobuf->ref) == 0);
 
                 LOCK_DESTROY (&iobuf->lock);
                 list_del_init (&iobuf->list);
@@ -529,23 +529,6 @@ out:
 
 
 struct iobuf *
-__iobuf_ref (struct iobuf *iobuf)
-{
-        iobuf->ref++;
-
-        return iobuf;
-}
-
-
-struct iobuf *
-__iobuf_unref (struct iobuf *iobuf)
-{
-        iobuf->ref--;
-
-        return iobuf;
-}
-
-struct iobuf *
 __iobuf_get (struct iobuf_arena *iobuf_arena, size_t page_size)
 {
         struct iobuf      *iobuf        = NULL;
@@ -619,7 +602,7 @@ iobuf_get_from_stdalloc (struct iobuf_pool *iobuf_pool, size_t page_size)
         LOCK_INIT (&iobuf->lock);
 
         /* Hold a ref because you are allocating and using it */
-        iobuf->ref = 1;
+        GF_ATOMIC_INIT (iobuf->ref, 1);
 
         ret = 0;
 out:
@@ -835,12 +818,7 @@ iobuf_unref (struct iobuf *iobuf)
 
         GF_VALIDATE_OR_GOTO ("iobuf", iobuf, out);
 
-        LOCK (&iobuf->lock);
-        {
-                __iobuf_unref (iobuf);
-                ref = iobuf->ref;
-        }
-        UNLOCK (&iobuf->lock);
+        ref = GF_ATOMIC_DEC (iobuf->ref);
 
         if (!ref)
                 iobuf_put (iobuf);
@@ -854,12 +832,7 @@ struct iobuf *
 iobuf_ref (struct iobuf *iobuf)
 {
         GF_VALIDATE_OR_GOTO ("iobuf", iobuf, out);
-
-        LOCK (&iobuf->lock);
-        {
-                __iobuf_ref (iobuf);
-        }
-        UNLOCK (&iobuf->lock);
+        GF_ATOMIC_INC (iobuf->ref);
 
 out:
         return iobuf;
@@ -888,8 +861,7 @@ iobref_new ()
 
         LOCK_INIT (&iobref->lock);
 
-        iobref->ref++;
-
+        GF_ATOMIC_INIT (iobref->ref, 1);
         return iobref;
 }
 
@@ -898,12 +870,7 @@ struct iobref *
 iobref_ref (struct iobref *iobref)
 {
         GF_VALIDATE_OR_GOTO ("iobuf", iobref, out);
-
-        LOCK (&iobref->lock);
-        {
-                iobref->ref++;
-        }
-        UNLOCK (&iobref->lock);
+        GF_ATOMIC_INC (iobref->ref);
 
 out:
         return iobref;
@@ -940,12 +907,7 @@ iobref_unref (struct iobref *iobref)
         int ref = 0;
 
         GF_VALIDATE_OR_GOTO ("iobuf", iobref, out);
-
-        LOCK (&iobref->lock);
-        {
-                ref = (--iobref->ref);
-        }
-        UNLOCK (&iobref->lock);
+        ref = GF_ATOMIC_DEC (iobref->ref);
 
         if (!ref)
                 iobref_destroy (iobref);
diff --git a/libglusterfs/src/iobuf.h b/libglusterfs/src/iobuf.h
index 03aa954bbdd..830904c2fe9 100644
--- a/libglusterfs/src/iobuf.h
+++ b/libglusterfs/src/iobuf.h
@@ -65,7 +65,7 @@ struct iobuf {
         struct iobuf_arena  *iobuf_arena;
 
         gf_lock_t            lock; /* for ->ptr and ->ref */
-        int                  ref;  /* 0 == passive, >0 == active */
+        gf_atomic_t          ref;  /* 0 == passive, >0 == active */
 
         void                *ptr;  /* usable memory region by the consumer */
 
@@ -150,7 +150,7 @@ void iobuf_to_iovec(struct iobuf *iob, struct iovec *iov);
 
 struct iobref {
         gf_lock_t          lock;
-        int                ref;
+        gf_atomic_t        ref;
         struct iobuf     **iobrefs;
 	int                alloced;
 	int                used;