in txn, use a "naked" value without an update record whenever possible

diff --git a/include/common.h b/include/common.h
index bf3d04ecc17a2960298f7916fd9b235f612a2cf1..faebe4c807160d7f093bb34a85acd0e584dcc305 100644 (file)
--- a/include/common.h
+++ b/include/common.h
@@ -31,10 +31,11 @@
 #define TRUE  1
 #define FALSE 0
 
 #define TRUE  1
 #define FALSE 0
 

-#define TAG          (1ULL << 63)
-#define TAG_VALUE(v) ((uint64_t)(v) |  TAG)
-#define IS_TAGGED(v) ((uint64_t)(v) &  TAG)
-#define STRIP_TAG(v) ((uint64_t)(v) & ~TAG)
+#define TAG1         (1ULL << 63)
+#define TAG2         (1ULL << 62)
+#define TAG_VALUE(v, tag) ((uint64_t)(v) |  tag)
+#define IS_TAGGED(v, tag) ((uint64_t)(v) &  tag)
+#define STRIP_TAG(v, tag) ((uint64_t)(v) & ~tag)

 
 #define DOES_NOT_EXIST 0
 #define ERROR_INVALID_OPTION (-1)
 
 #define DOES_NOT_EXIST 0
 #define ERROR_INVALID_OPTION (-1)

diff --git a/makefile b/makefile
index ba6ad3184dc71b240a6ce50c0f5dcc4ae94ea17e..82d921ebd2b15365a28b456437c50cd94c42e188 100644 (file)
--- a/makefile
+++ b/makefile
@@ -7,7 +7,7 @@
 OPT       := -fwhole-program -combine -03 #-DNDEBUG
 CFLAGS := -g -Wall -Werror -std=c99 -m64 $(OPT) #-DENABLE_TRACE
 INCS   := $(addprefix -I, include)
 OPT       := -fwhole-program -combine -03 #-DNDEBUG
 CFLAGS := -g -Wall -Werror -std=c99 -m64 $(OPT) #-DENABLE_TRACE
 INCS   := $(addprefix -I, include)

-TESTS  := output/map_test1 output/map_test2 output/rcu_test output/txn_test
+TESTS  := output/map_test1 output/map_test2 output/txn_test

 EXES   := $(TESTS)
 
 RUNTIME_SRCS := runtime/runtime.c runtime/rcu.c runtime/lwt.c runtime/mem.c datatype/nstring.c 
 EXES   := $(TESTS)
 
 RUNTIME_SRCS := runtime/runtime.c runtime/rcu.c runtime/lwt.c runtime/mem.c datatype/nstring.c 

diff --git a/map/hashtable.c b/map/hashtable.c
index 17339415cc44cd0030ddba4f804a12a7d101494d..f9bf715e7aeeee79310c8e9e3256a21a30258af3 100644 (file)
--- a/map/hashtable.c
+++ b/map/hashtable.c
@@ -42,7 +42,7 @@ struct ht {
 };
 
 static const uint64_t COPIED_VALUE           = -1;
 };
 
 static const uint64_t COPIED_VALUE           = -1;

-static const uint64_t TOMBSTONE              = STRIP_TAG(-1);
+static const uint64_t TOMBSTONE              = STRIP_TAG(-1, TAG1);

 
 static const unsigned ENTRIES_PER_BUCKET     = CACHE_LINE_SIZE/sizeof(entry_t);
 static const unsigned ENTRIES_PER_COPY_CHUNK = CACHE_LINE_SIZE/sizeof(entry_t)*2;
 
 static const unsigned ENTRIES_PER_BUCKET     = CACHE_LINE_SIZE/sizeof(entry_t);
 static const unsigned ENTRIES_PER_COPY_CHUNK = CACHE_LINE_SIZE/sizeof(entry_t)*2;


@@ -201,7 +201,7 @@ static int hti_copy_entry (hti_t *ht1, volatile entry_t *ht1_ent, uint32_t key_h
     }
 
     // Tag the value in the old entry to indicate a copy is in progress.
     }
 
     // Tag the value in the old entry to indicate a copy is in progress.

-    ht1_ent_val = SYNC_FETCH_AND_OR(&ht1_ent->val, TAG_VALUE(0));
+    ht1_ent_val = SYNC_FETCH_AND_OR(&ht1_ent->val, TAG_VALUE(0, TAG1));

     TRACE("h2", "hti_copy_entry: tagged the value %p in old entry %p", ht1_ent_val, ht1_ent);
     if (ht1_ent_val == COPIED_VALUE) {
         TRACE("h1", "hti_copy_entry: entry %p already copied to table %p", ht1_ent, ht2);
     TRACE("h2", "hti_copy_entry: tagged the value %p in old entry %p", ht1_ent_val, ht1_ent);
     if (ht1_ent_val == COPIED_VALUE) {
         TRACE("h1", "hti_copy_entry: entry %p already copied to table %p", ht1_ent, ht2);


@@ -213,7 +213,7 @@ static int hti_copy_entry (hti_t *ht1, volatile entry_t *ht1_ent, uint32_t key_h
     void *key = (ht1->ht->key_type == NULL) ? (void *)ht1_ent_key : GET_PTR(ht1_ent_key);
 
     // The old table's dead entries don't need to be copied to the new table, but their keys need to be freed.
     void *key = (ht1->ht->key_type == NULL) ? (void *)ht1_ent_key : GET_PTR(ht1_ent_key);
 
     // The old table's dead entries don't need to be copied to the new table, but their keys need to be freed.

-    assert(COPIED_VALUE == TAG_VALUE(TOMBSTONE));
+    assert(COPIED_VALUE == TAG_VALUE(TOMBSTONE, TAG1));

     if (ht1_ent_val == TOMBSTONE) {
         TRACE("h1", "hti_copy_entry: entry %p old value was deleted, now freeing key %p", ht1_ent, key);
         if (EXPECT_FALSE(ht1->ht->key_type != NULL)) {
     if (ht1_ent_val == TOMBSTONE) {
         TRACE("h1", "hti_copy_entry: entry %p old value was deleted, now freeing key %p", ht1_ent, key);
         if (EXPECT_FALSE(ht1->ht->key_type != NULL)) {


@@ -251,7 +251,7 @@ static int hti_copy_entry (hti_t *ht1, volatile entry_t *ht1_ent, uint32_t key_h
     }
 
     // Copy the value to the entry in the new table.
     }
 
     // Copy the value to the entry in the new table.

-    ht1_ent_val = STRIP_TAG(ht1_ent_val);
+    ht1_ent_val = STRIP_TAG(ht1_ent_val, TAG1);

     uint64_t old_ht2_ent_val = SYNC_CAS(&ht2_ent->val, DOES_NOT_EXIST, ht1_ent_val);
 
     // If there is a nested copy in progress, we might have installed the key into a dead entry.
     uint64_t old_ht2_ent_val = SYNC_CAS(&ht2_ent->val, DOES_NOT_EXIST, ht1_ent_val);
 
     // If there is a nested copy in progress, we might have installed the key into a dead entry.


@@ -294,7 +294,7 @@ static uint64_t hti_cas (hti_t *hti, void *key, uint32_t key_hash, uint64_t expe
     TRACE("h1", "hti_cas: hti %p key %p", hti, key);
     TRACE("h1", "hti_cas: value %p expect %p", new, expected);
     assert(hti);
     TRACE("h1", "hti_cas: hti %p key %p", hti, key);
     TRACE("h1", "hti_cas: value %p expect %p", new, expected);
     assert(hti);

-    assert(!IS_TAGGED(new));
+    assert(!IS_TAGGED(new, TAG1));

     assert(key);
 
     int is_empty;
     assert(key);
 
     int is_empty;


@@ -346,7 +346,7 @@ static uint64_t hti_cas (hti_t *hti, void *key, uint32_t key_hash, uint64_t expe
 
     // If the entry is in the middle of a copy, the copy must be completed first.
     uint64_t ent_val = ent->val;
 
     // If the entry is in the middle of a copy, the copy must be completed first.
     uint64_t ent_val = ent->val;

-    if (EXPECT_FALSE(IS_TAGGED(ent_val))) {
+    if (EXPECT_FALSE(IS_TAGGED(ent_val, TAG1))) {

         if (ent_val != COPIED_VALUE) {
             int did_copy = hti_copy_entry(hti, ent, key_hash, ((volatile hti_t *)hti)->next);
             if (did_copy) {
         if (ent_val != COPIED_VALUE) {
             int did_copy = hti_copy_entry(hti, ent, key_hash, ((volatile hti_t *)hti)->next);
             if (did_copy) {


@@ -413,7 +413,7 @@ static uint64_t hti_get (hti_t *hti, void *key, uint32_t key_hash) {
 
     // If the entry is being copied, finish the copy and retry on the next table.
     uint64_t ent_val = ent->val;
 
     // If the entry is being copied, finish the copy and retry on the next table.
     uint64_t ent_val = ent->val;

-    if (EXPECT_FALSE(IS_TAGGED(ent_val))) {
+    if (EXPECT_FALSE(IS_TAGGED(ent_val, TAG1))) {

         if (EXPECT_FALSE(ent_val != COPIED_VALUE)) {
             int did_copy = hti_copy_entry(hti, ent, key_hash, ((volatile hti_t *)hti)->next);
             if (did_copy) {
         if (EXPECT_FALSE(ent_val != COPIED_VALUE)) {
             int did_copy = hti_copy_entry(hti, ent, key_hash, ((volatile hti_t *)hti)->next);
             if (did_copy) {


@@ -438,7 +438,7 @@ uint64_t ht_cas (hashtable_t *ht, void *key, uint64_t expected_val, uint64_t new
     TRACE("h2", "ht_cas: key %p ht %p", key, ht);
     TRACE("h2", "ht_cas: expected val %p new val %p", expected_val, new_val);
     assert(key != DOES_NOT_EXIST);
     TRACE("h2", "ht_cas: key %p ht %p", key, ht);
     TRACE("h2", "ht_cas: expected val %p new val %p", expected_val, new_val);
     assert(key != DOES_NOT_EXIST);

-    assert(!IS_TAGGED(new_val) && new_val != DOES_NOT_EXIST && new_val != TOMBSTONE);
+    assert(!IS_TAGGED(new_val, TAG1) && new_val != DOES_NOT_EXIST && new_val != TOMBSTONE);

 
     hti_t *hti = ht->hti;
 
 
     hti_t *hti = ht->hti;
 


@@ -538,7 +538,7 @@ void ht_free (hashtable_t *ht) {
     hti_t *hti = ht->hti;
     do {
         for (uint32_t i = 0; i < (1 << hti->scale); ++i) {
     hti_t *hti = ht->hti;
     do {
         for (uint32_t i = 0; i < (1 << hti->scale); ++i) {

-            assert(hti->table[i].val == COPIED_VALUE || !IS_TAGGED(hti->table[i].val));
+            assert(hti->table[i].val == COPIED_VALUE || !IS_TAGGED(hti->table[i].val, TAG1));

             if (ht->key_type != NULL && hti->table[i].key != DOES_NOT_EXIST) {
                 nbd_free(GET_PTR(hti->table[i].key));
             }
             if (ht->key_type != NULL && hti->table[i].key != DOES_NOT_EXIST) {
                 nbd_free(GET_PTR(hti->table[i].key));
             }

diff --git a/map/list.c b/map/list.c
index 0982e59810bab669599a20583e52cb9df9768f69..a94d2d00594274b2e2b7b661b697667ab8802d26 100644 (file)
--- a/map/list.c
+++ b/map/list.c
@@ -42,7 +42,7 @@ list_t *ll_alloc (const datatype_t *key_type) {
 void ll_free (list_t *ll) {
     node_t *item = ll->head->next;
     while (item) {
 void ll_free (list_t *ll) {
     node_t *item = ll->head->next;
     while (item) {

-        node_t *next = (node_t *)STRIP_TAG(item->next);
+        node_t *next = (node_t *)STRIP_TAG(item->next, TAG1);

         nbd_free(item);
         item = next;
     }
         nbd_free(item);
         item = next;
     }


@@ -52,10 +52,10 @@ uint64_t ll_count (list_t *ll) {
     uint64_t count = 0;
     node_t *item = ll->head->next;
     while (item) {
     uint64_t count = 0;
     node_t *item = ll->head->next;
     while (item) {

-        if (!IS_TAGGED(item->next)) {
+        if (!IS_TAGGED(item->next, TAG1)) {

             count++;
         }
             count++;
         }

-        item = (node_t *)STRIP_TAG(item->next);
+        item = (node_t *)STRIP_TAG(item->next, TAG1);

     }
     return count;
 }
     }
     return count;
 }


@@ -69,11 +69,11 @@ static int find_pred (node_t **pred_ptr, node_t **item_ptr, list_t *ll, void *ke
         node_t *next = item->next;
 
         // A tag means an item is logically removed but not physically unlinked yet.
         node_t *next = item->next;
 
         // A tag means an item is logically removed but not physically unlinked yet.

-        while (EXPECT_FALSE(IS_TAGGED(next))) {
+        while (EXPECT_FALSE(IS_TAGGED(next, TAG1))) {

 
             // Skip over logically removed items.
             if (!help_remove) {
 
             // Skip over logically removed items.
             if (!help_remove) {

-                item = (node_t *)STRIP_TAG(item->next);
+                item = (node_t *)STRIP_TAG(item->next, TAG1);

                 if (EXPECT_FALSE(item == NULL))
                     break;
                 TRACE("l3", "find_pred: skipping marked item %p (next is %p)", item, next);
                 if (EXPECT_FALSE(item == NULL))
                     break;
                 TRACE("l3", "find_pred: skipping marked item %p (next is %p)", item, next);


@@ -84,9 +84,9 @@ static int find_pred (node_t **pred_ptr, node_t **item_ptr, list_t *ll, void *ke
             // Unlink logically removed items.
             node_t *other;
             TRACE("l3", "find_pred: unlinking marked item %p next is %p", item, next);
             // Unlink logically removed items.
             node_t *other;
             TRACE("l3", "find_pred: unlinking marked item %p next is %p", item, next);

-            if ((other = SYNC_CAS(&pred->next, item, STRIP_TAG(next))) == item) {
+            if ((other = SYNC_CAS(&pred->next, item, STRIP_TAG(next, TAG1))) == item) {

                 TRACE("l2", "find_pred: unlinked item %p from pred %p", item, pred);
                 TRACE("l2", "find_pred: unlinked item %p from pred %p", item, pred);

-                item = (node_t *)STRIP_TAG(next);
+                item = (node_t *)STRIP_TAG(next, TAG1);

                 if (EXPECT_FALSE(item == NULL))
                     break;
                 next = item->next;
                 if (EXPECT_FALSE(item == NULL))
                     break;
                 next = item->next;


@@ -100,7 +100,7 @@ static int find_pred (node_t **pred_ptr, node_t **item_ptr, list_t *ll, void *ke
             } else {
                 TRACE("l2", "find_pred: lost a race to unlink item %p from pred %p", item, pred);
                 TRACE("l2", "find_pred: pred's link changed to %p", other, 0);
             } else {
                 TRACE("l2", "find_pred: lost a race to unlink item %p from pred %p", item, pred);
                 TRACE("l2", "find_pred: pred's link changed to %p", other, 0);

-                if (IS_TAGGED(other))
+                if (IS_TAGGED(other, TAG1))

                     return find_pred(pred_ptr, item_ptr, ll, key, help_remove); // retry
                 item = other;
                 if (EXPECT_FALSE(item == NULL))
                     return find_pred(pred_ptr, item_ptr, ll, key, help_remove); // retry
                 item = other;
                 if (EXPECT_FALSE(item == NULL))


@@ -252,14 +252,14 @@ uint64_t ll_remove (list_t *ll, void *key) {
     node_t *old_next = item->next;
     do {
         next = old_next;
     node_t *old_next = item->next;
     do {
         next = old_next;

-        old_next = SYNC_CAS(&item->next, next, TAG_VALUE(next));
-        if (IS_TAGGED(old_next)) {
+        old_next = SYNC_CAS(&item->next, next, TAG_VALUE(next, TAG1));
+        if (IS_TAGGED(old_next, TAG1)) {

             TRACE("l1", "ll_remove: lost a race -- %p is already marked for removal by another thread", item, 0);
             return DOES_NOT_EXIST;
         }
     } while (next != old_next);
     TRACE("l2", "ll_remove: logically removed item %p", item, 0);
             TRACE("l1", "ll_remove: lost a race -- %p is already marked for removal by another thread", item, 0);
             return DOES_NOT_EXIST;
         }
     } while (next != old_next);
     TRACE("l2", "ll_remove: logically removed item %p", item, 0);

-    ASSERT(IS_TAGGED(item->next));
+    ASSERT(IS_TAGGED(item->next, TAG1));

 
     // Atomically swap out the item's value in case another thread is updating the item while we are 
     // removing it. This establishes which operation occurs first logically, the update or the remove. 
 
     // Atomically swap out the item's value in case another thread is updating the item while we are 
     // removing it. This establishes which operation occurs first logically, the update or the remove. 


@@ -291,12 +291,12 @@ void ll_print (list_t *ll) {
     int i = 0;
     while (item) {
         node_t *next = item->next;
     int i = 0;
     while (item) {
         node_t *next = item->next;

-        if (IS_TAGGED(item)) {
+        if (IS_TAGGED(item, TAG1)) {

             printf("*");
         }
         printf("%p:%p ", item, item->key);
         fflush(stdout);
             printf("*");
         }
         printf("%p:%p ", item, item->key);
         fflush(stdout);

-        item = (node_t *)STRIP_TAG(next);
+        item = (node_t *)STRIP_TAG(next, TAG1);

         if (i++ > 30) {
             printf("...");
             break;
         if (i++ > 30) {
             printf("...");
             break;

diff --git a/map/skiplist.c b/map/skiplist.c
index 49ef21b3d32bcfe43c0e38cfdad883be1994eda5..62506e146e88aa5a5d58665d7524890fa3357ed5 100644 (file)
--- a/map/skiplist.c
+++ b/map/skiplist.c
@@ -74,7 +74,7 @@ skiplist_t *sl_alloc (const datatype_t *key_type) {
 void sl_free (skiplist_t *sl) {
     node_t *item = sl->head->next[0];
     while (item) {
 void sl_free (skiplist_t *sl) {
     node_t *item = sl->head->next[0];
     while (item) {

-        node_t *next = (node_t *)STRIP_TAG(item->next[0]);
+        node_t *next = (node_t *)STRIP_TAG(item->next[0], TAG1);

         nbd_free(item);
         item = next;
     }
         nbd_free(item);
         item = next;
     }


@@ -84,10 +84,10 @@ uint64_t sl_count (skiplist_t *sl) {
     uint64_t count = 0;
     node_t *item = sl->head->next[0];
     while (item) {
     uint64_t count = 0;
     node_t *item = sl->head->next[0];
     while (item) {

-        if (!IS_TAGGED(item->next[0])) {
+        if (!IS_TAGGED(item->next[0], TAG1)) {

             count++;
         }
             count++;
         }

-        item = (node_t *)STRIP_TAG(item->next[0]);
+        item = (node_t *)STRIP_TAG(item->next[0], TAG1);

     }
     return count;
 }
     }
     return count;
 }


@@ -117,7 +117,7 @@ static node_t *find_preds (node_t **preds, node_t **succs, int n, skiplist_t *sl
     for (int level = start_level; level >= 0; --level) {
         TRACE("s3", "find_preds: level %llu", level, 0);
         item = pred->next[level];
     for (int level = start_level; level >= 0; --level) {
         TRACE("s3", "find_preds: level %llu", level, 0);
         item = pred->next[level];

-        if (EXPECT_FALSE(IS_TAGGED(item))) {
+        if (EXPECT_FALSE(IS_TAGGED(item, TAG1))) {

             TRACE("s2", "find_preds: pred %p is marked for removal (item %p); retry", pred, item);
             return find_preds(preds, succs, n, sl, key, help_remove); // retry
         }
             TRACE("s2", "find_preds: pred %p is marked for removal (item %p); retry", pred, item);
             return find_preds(preds, succs, n, sl, key, help_remove); // retry
         }


@@ -125,11 +125,11 @@ static node_t *find_preds (node_t **preds, node_t **succs, int n, skiplist_t *sl
             node_t *next = item->next[level];
 
             // A tag means an item is logically removed but not physically unlinked yet.
             node_t *next = item->next[level];
 
             // A tag means an item is logically removed but not physically unlinked yet.

-            while (EXPECT_FALSE(IS_TAGGED(next))) {
+            while (EXPECT_FALSE(IS_TAGGED(next, TAG1))) {

 
                 // Skip over logically removed items.
                 if (!help_remove) {
 
                 // Skip over logically removed items.
                 if (!help_remove) {

-                    item = (node_t *)STRIP_TAG(item->next);
+                    item = (node_t *)STRIP_TAG(item->next, TAG1);

                     if (EXPECT_FALSE(item == NULL))
                         break;
                     TRACE("s3", "find_preds: skipping marked item %p (next is %p)", item, next);
                     if (EXPECT_FALSE(item == NULL))
                         break;
                     TRACE("s3", "find_preds: skipping marked item %p (next is %p)", item, next);


@@ -140,8 +140,8 @@ static node_t *find_preds (node_t **preds, node_t **succs, int n, skiplist_t *sl
                 // Unlink logically removed items.
                 node_t *other;
                 TRACE("s3", "find_preds: unlinking marked item %p; next is %p", item, next);
                 // Unlink logically removed items.
                 node_t *other;
                 TRACE("s3", "find_preds: unlinking marked item %p; next is %p", item, next);

-                if ((other = SYNC_CAS(&pred->next[level], item, STRIP_TAG(next))) == item) {
-                    item = (node_t *)STRIP_TAG(next);
+                if ((other = SYNC_CAS(&pred->next[level], item, STRIP_TAG(next, TAG1))) == item) {
+                    item = (node_t *)STRIP_TAG(next, TAG1);

                     if (EXPECT_FALSE(item == NULL))
                         break;
                     next = item->next[level];
                     if (EXPECT_FALSE(item == NULL))
                         break;
                     next = item->next[level];


@@ -157,7 +157,7 @@ static node_t *find_preds (node_t **preds, node_t **succs, int n, skiplist_t *sl
                 } else {
                     TRACE("s3", "find_preds: lost race to unlink item %p from pred %p", item, pred);
                     TRACE("s3", "find_preds: pred's link changed to %p", other, 0);
                 } else {
                     TRACE("s3", "find_preds: lost race to unlink item %p from pred %p", item, pred);
                     TRACE("s3", "find_preds: pred's link changed to %p", other, 0);

-                    if (IS_TAGGED(other))
+                    if (IS_TAGGED(other, TAG1))

                         return find_preds(preds, succs, n, sl, key, help_remove); // retry
                     item = other;
                     if (EXPECT_FALSE(item == NULL))
                         return find_preds(preds, succs, n, sl, key, help_remove); // retry
                     item = other;
                     if (EXPECT_FALSE(item == NULL))


@@ -170,7 +170,7 @@ static node_t *find_preds (node_t **preds, node_t **succs, int n, skiplist_t *sl
                 break;
 
             TRACE("s4", "find_preds: visiting item %p (next is %p)", item, next);
                 break;
 
             TRACE("s4", "find_preds: visiting item %p (next is %p)", item, next);

-            TRACE("s4", "find_preds: key %p val %p", STRIP_TAG(item->key), item->val);
+            TRACE("s4", "find_preds: key %p val %p", STRIP_TAG(item->key, TAG1), item->val);

 
             if (EXPECT_TRUE(sl->key_type == NULL)) {
                 d = (uint64_t)item->key - (uint64_t)key;
 
             if (EXPECT_TRUE(sl->key_type == NULL)) {
                 d = (uint64_t)item->key - (uint64_t)key;


@@ -235,9 +235,9 @@ void *sl_min_key (skiplist_t *sl) {
     node_t *item = sl->head->next[0];
     while (item != NULL) {
         node_t *next = item->next[0];
     node_t *item = sl->head->next[0];
     while (item != NULL) {
         node_t *next = item->next[0];

-        if (!IS_TAGGED(next))
+        if (!IS_TAGGED(next, TAG1))

             return item->key;
             return item->key;

-        item = (node_t *)STRIP_TAG(next);
+        item = (node_t *)STRIP_TAG(next, TAG1);

     }
     return DOES_NOT_EXIST;
 }
     }
     return DOES_NOT_EXIST;
 }


@@ -335,7 +335,7 @@ uint64_t sl_cas (skiplist_t *sl, void *key, uint64_t expectation, uint64_t new_v
             do {
                 // There in no need to continue linking in the item if another thread removed it.
                 node_t *old_next = ((volatile node_t *)new_item)->next[level];
             do {
                 // There in no need to continue linking in the item if another thread removed it.
                 node_t *old_next = ((volatile node_t *)new_item)->next[level];

-                if (IS_TAGGED(old_next))
+                if (IS_TAGGED(old_next, TAG1))

                     return DOES_NOT_EXIST; // success
 
                 // Use a CAS so we do not inadvertantly stomp on a mark another thread placed on the item.
                     return DOES_NOT_EXIST; // success
 
                 // Use a CAS so we do not inadvertantly stomp on a mark another thread placed on the item.


@@ -363,17 +363,17 @@ uint64_t sl_remove (skiplist_t *sl, void *key) {
         node_t *old_next = item->next[level];
         do {
             next = old_next;
         node_t *old_next = item->next[level];
         do {
             next = old_next;

-            old_next = SYNC_CAS(&item->next[level], next, TAG_VALUE(next));
-            if (IS_TAGGED(old_next)) {
+            old_next = SYNC_CAS(&item->next[level], next, TAG_VALUE(next, TAG1));
+            if (IS_TAGGED(old_next, TAG1)) {

                 TRACE("s2", "sl_remove: %p is already marked for removal by another thread at level %llu", item, level);
                 break;
             }
         } while (next != old_next);
 
         node_t *pred = preds[level];
                 TRACE("s2", "sl_remove: %p is already marked for removal by another thread at level %llu", item, level);
                 break;
             }
         } while (next != old_next);
 
         node_t *pred = preds[level];

-        TRACE("s2", "sl_remove: linking the item's pred %p to the item's successor %p", pred, STRIP_TAG(next));
+        TRACE("s2", "sl_remove: linking the item's pred %p to the item's successor %p", pred, STRIP_TAG(next, TAG1));

         node_t *other = NULL;
         node_t *other = NULL;

-        if ((other = SYNC_CAS(&pred->next[level], item, STRIP_TAG(next))) != item) {
+        if ((other = SYNC_CAS(&pred->next[level], item, STRIP_TAG(next, TAG1))) != item) {

             TRACE("s1", "sl_remove: unlink failed; pred's link changed from %p to %p", item, other);
             // If our former predecessor now points past us we know another thread unlinked us. Otherwise, we need
             // to search for a new set of preds.
             TRACE("s1", "sl_remove: unlink failed; pred's link changed from %p to %p", item, other);
             // If our former predecessor now points past us we know another thread unlinked us. Otherwise, we need
             // to search for a new set of preds.


@@ -381,7 +381,7 @@ uint64_t sl_remove (skiplist_t *sl, void *key) {
                 continue; // <pred> points past <item> to the end of the list; go on to the next level.
 
             int d = -1;
                 continue; // <pred> points past <item> to the end of the list; go on to the next level.
 
             int d = -1;

-            if (!IS_TAGGED(other)) {
+            if (!IS_TAGGED(other, TAG1)) {

                 if (EXPECT_TRUE(sl->key_type == NULL)) {
                     d = (uint64_t)item->key - (uint64_t)other->key;
                 } else {
                 if (EXPECT_TRUE(sl->key_type == NULL)) {
                     d = (uint64_t)item->key - (uint64_t)other->key;
                 } else {


@@ -401,8 +401,8 @@ uint64_t sl_remove (skiplist_t *sl, void *key) {
     node_t *old_next = item->next[0];
     do {
         next = old_next;
     node_t *old_next = item->next[0];
     do {
         next = old_next;

-        old_next = SYNC_CAS(&item->next[0], next, TAG_VALUE(next));
-        if (IS_TAGGED(old_next)) {
+        old_next = SYNC_CAS(&item->next[0], next, TAG_VALUE(next, TAG1));
+        if (IS_TAGGED(old_next, TAG1)) {

             TRACE("s2", "sl_remove: %p is already marked for removal by another thread at level 0", item, 0);
             return DOES_NOT_EXIST;
         }
             TRACE("s2", "sl_remove: %p is already marked for removal by another thread at level 0", item, 0);
             return DOES_NOT_EXIST;
         }


@@ -415,8 +415,8 @@ uint64_t sl_remove (skiplist_t *sl, void *key) {
     TRACE("s2", "sl_remove: replaced item %p's value with DOES_NOT_EXIT", item, 0);
 
     node_t *pred = preds[0];
     TRACE("s2", "sl_remove: replaced item %p's value with DOES_NOT_EXIT", item, 0);
 
     node_t *pred = preds[0];

-    TRACE("s2", "sl_remove: linking the item's pred %p to the item's successor %p", pred, STRIP_TAG(next));
-    if (SYNC_CAS(&pred->next[0], item, STRIP_TAG(next))) {
+    TRACE("s2", "sl_remove: linking the item's pred %p to the item's successor %p", pred, STRIP_TAG(next, TAG1));
+    if (SYNC_CAS(&pred->next[0], item, STRIP_TAG(next, TAG1))) {

         TRACE("s2", "sl_remove: unlinked item %p from the skiplist at level 0", item, 0);
         // The thread that completes the unlink should free the memory.
         if (sl->key_type != NULL) {
         TRACE("s2", "sl_remove: unlinked item %p from the skiplist at level 0", item, 0);
         // The thread that completes the unlink should free the memory.
         if (sl->key_type != NULL) {


@@ -436,8 +436,8 @@ void sl_print (skiplist_t *sl) {
         int i = 0;
         while (item) {
             node_t *next = item->next[level];
         int i = 0;
         while (item) {
             node_t *next = item->next[level];

-            printf("%s%p ", IS_TAGGED(next) ? "*" : "", item);
-            item = (node_t *)STRIP_TAG(next);
+            printf("%s%p ", IS_TAGGED(next, TAG1) ? "*" : "", item);
+            item = (node_t *)STRIP_TAG(next, TAG1);

             if (i++ > 30) {
                 printf("...");
                 break;
             if (i++ > 30) {
                 printf("...");
                 break;


@@ -449,7 +449,7 @@ void sl_print (skiplist_t *sl) {
     node_t *item = sl->head;
     int i = 0;
     while (item) {
     node_t *item = sl->head;
     int i = 0;
     while (item) {

-        int is_marked = IS_TAGGED(item->next[0]);
+        int is_marked = IS_TAGGED(item->next[0], TAG1);

         printf("%s%p:%p ", is_marked ? "*" : "", item, item->key);
         if (item != sl->head) {
             printf("[%d]", item->top_level);
         printf("%s%p:%p ", is_marked ? "*" : "", item, item->key);
         if (item != sl->head) {
             printf("[%d]", item->top_level);


@@ -457,15 +457,15 @@ void sl_print (skiplist_t *sl) {
             printf("[HEAD]");
         }
         for (int level = 1; level <= item->top_level; ++level) {
             printf("[HEAD]");
         }
         for (int level = 1; level <= item->top_level; ++level) {

-            node_t *next = (node_t *)STRIP_TAG(item->next[level]);
-            is_marked = IS_TAGGED(item->next[0]);
+            node_t *next = (node_t *)STRIP_TAG(item->next[level], TAG1);
+            is_marked = IS_TAGGED(item->next[0], TAG1);

             printf(" %p%s", next, is_marked ? "*" : "");
             if (item == sl->head && item->next[level] == NULL)
                 break;
         }
         printf("\n");
         fflush(stdout);
             printf(" %p%s", next, is_marked ? "*" : "");
             if (item == sl->head && item->next[level] == NULL)
                 break;
         }
         printf("\n");
         fflush(stdout);

-        item = (node_t *)STRIP_TAG(item->next[0]);
+        item = (node_t *)STRIP_TAG(item->next[0], TAG1);

         if (i++ > 30) {
             printf("...\n");
             break;
         if (i++ > 30) {
             printf("...\n");
             break;

diff --git a/txn/txn.c b/txn/txn.c
index 991c22c8a8351002922df123cc6413c925676a5f..ea3d6df4ccbb5729fc0447218979b0bafbee703e 100644 (file)
--- a/txn/txn.c
+++ b/txn/txn.c
@@ -8,23 +8,20 @@
 #include "skiplist.h"
 
 #define UNDETERMINED_VERSION 0
 #include "skiplist.h"
 
 #define UNDETERMINED_VERSION 0

-#define ABORTED_VERSION      TAG_VALUE(0)
+#define ABORTED_VERSION      TAG_VALUE(0, TAG1)

 #define INITIAL_WRITES_SIZE  4
 
 #define INITIAL_WRITES_SIZE  4
 

-typedef enum { UPDATE_TYPE_PUT, UPDATE_TYPE_DELETE } update_type_t;
-
-typedef struct update_rec update_rec_t;
+typedef struct update_rec update_t;

 
 struct update_rec {
 
 struct update_rec {

-    update_type_t type;
-    uint64_t value;
+    update_t *next; // an earlier update

     uint64_t version;
     uint64_t version;

-    update_rec_t *next; // an earlier update
+    uint64_t value;

 };
 
 typedef struct write_rec {
     void *key;
 };
 
 typedef struct write_rec {
     void *key;

-    update_rec_t *rec; 
+    update_t *rec; 

 } write_rec_t;
 
 struct txn {
 } write_rec_t;
 
 struct txn {


@@ -57,15 +54,18 @@ void txn_init (void) {
 //
 static txn_state_e tm_validate_key (txn_t *txn, void *key) {
     
 //
 static txn_state_e tm_validate_key (txn_t *txn, void *key) {
     

-    update_rec_t *update = (update_rec_t *) map_get(txn->map, key);
+    update_t *update = (update_t *) map_get(txn->map, key);

     for (; update != NULL; update = update->next) {
 
     for (; update != NULL; update = update->next) {
 

-        // If the update's version is not tagged it means the update is committed.
+        // If the update or its version is not tagged it means the update is committed.

         //
         // We can stop at the first committed record we find that is at least as old as our read version. All 
         // the other committed records following it will be older. And all the uncommitted records following it 
         // will eventually conflict with it and abort.
         //
         // We can stop at the first committed record we find that is at least as old as our read version. All 
         // the other committed records following it will be older. And all the uncommitted records following it 
         // will eventually conflict with it and abort.

-        if (!IS_TAGGED(update->version)) 
+        if (!IS_TAGGED(update, TAG2))
+            return TXN_VALIDATED;
+        update = (update_t *)STRIP_TAG(update, TAG2);
+        if (!IS_TAGGED(update->version, TAG1)) 

             return (update->version <= txn->rv) ? TXN_VALIDATED : TXN_ABORTED;
 
         // If the update's version is tagged then either the update was aborted or the the version number is 
             return (update->version <= txn->rv) ? TXN_VALIDATED : TXN_ABORTED;
 
         // If the update's version is tagged then either the update was aborted or the the version number is 


@@ -76,12 +76,12 @@ static txn_state_e tm_validate_key (txn_t *txn, void *key) {
             continue;
 
         // The update's transaction is still in progress. Access its txn_t.
             continue;
 
         // The update's transaction is still in progress. Access its txn_t.

-        txn_t *writer = (txn_t *)STRIP_TAG(update->version);
+        txn_t *writer = (txn_t *)STRIP_TAG(update->version, TAG1);

         if (writer == txn)
             continue; // Skip our own updates.
         txn_state_e writer_state = writer->state;
 
         if (writer == txn)
             continue; // Skip our own updates.
         txn_state_e writer_state = writer->state;
 

-        // Any running transaction will only be able to aquire a wv greater than ours. A transaction changes its 
+        // Any running transaction will only be able to acquire a wv greater than ours. A transaction changes its 

         // state to validating before aquiring a wv. We can ignore an unvalidated transaction if its version is
         // greater than ours. See next comment below for why. 
         if (writer_state == TXN_RUNNING)
         // state to validating before aquiring a wv. We can ignore an unvalidated transaction if its version is
         // greater than ours. See next comment below for why. 
         if (writer_state == TXN_RUNNING)


@@ -143,9 +143,9 @@ static txn_state_e txn_validate (txn_t *txn) {
     return txn->state;
 }
 
     return txn->state;
 }
 

-static update_rec_t *alloc_update_rec (void) {
-    update_rec_t *u = (update_rec_t *)nbd_malloc(sizeof(update_rec_t));
-    memset(u, 0, sizeof(update_rec_t));
+static update_t *alloc_update_rec (void) {
+    update_t *u = (update_t *)nbd_malloc(sizeof(update_t));
+    memset(u, 0, sizeof(update_t));

     return u;
 }
 
     return u;
 }
 


@@ -161,7 +161,7 @@ txn_t *txn_begin (txn_type_e type, map_t *map) {
         txn->writes_size = INITIAL_WRITES_SIZE;
     }
 
         txn->writes_size = INITIAL_WRITES_SIZE;
     }
 

-    // aquire the read version for txn. must be careful to avoid a race
+    // acquire the read version for txn. must be careful to avoid a race

     do {
         txn->rv = version_;
 
     do {
         txn->rv = version_;
 


@@ -189,7 +189,7 @@ void txn_abort (txn_t *txn) {
 
     int i;
     for (i = 0; i < txn->writes_count; ++i) {
 
     int i;
     for (i = 0; i < txn->writes_count; ++i) {

-        update_rec_t *update = (update_rec_t *)txn->writes[i].rec;
+        update_t *update = (update_t *)txn->writes[i].rec;

         update->version = ABORTED_VERSION;
     }
 
         update->version = ABORTED_VERSION;
     }
 


@@ -207,7 +207,7 @@ txn_state_e txn_commit (txn_t *txn) {
     uint64_t wv = (txn->state == TXN_ABORTED) ? ABORTED_VERSION : txn->wv;
     int i;
     for (i = 0; i < txn->writes_count; ++i) {
     uint64_t wv = (txn->state == TXN_ABORTED) ? ABORTED_VERSION : txn->wv;
     int i;
     for (i = 0; i < txn->writes_count; ++i) {

-        update_rec_t *update = (update_rec_t *)txn->writes[i].rec;
+        update_t *update = (update_t *)txn->writes[i].rec;

         update->version = wv;
     }
 
         update->version = wv;
     }
 


@@ -232,13 +232,22 @@ txn_state_e txn_commit (txn_t *txn) {
 // Get most recent committed version prior to our read version.
 uint64_t tm_get (txn_t *txn, void *key) {
 
 // Get most recent committed version prior to our read version.
 uint64_t tm_get (txn_t *txn, void *key) {
 

-    // Iterate through update records associated with <key> to find the latest committed version prior to our
-    // read version. 
-    update_rec_t *update = (update_rec_t *) map_get(txn->map, key);
-    for (; update != NULL; update = update->next) {
+    update_t *newest_update = (update_t *) map_get(txn->map, key);
+    if (!IS_TAGGED(newest_update, TAG2))
+            return (uint64_t)newest_update;
+
+    // Iterate through the update records to find the latest committed version prior to our read version. 
+    update_t *update;
+    for (update = newest_update; ; update = update->next) {
+
+        if (!IS_TAGGED(update, TAG2))
+            return (uint64_t)update;
+
+        update = (update_t *)STRIP_TAG(update, TAG2);
+        assert(update != NULL);

 
         // If the update's version is not tagged it means the update is committed.
 
         // If the update's version is not tagged it means the update is committed.

-        if (!IS_TAGGED(update->version)) {
+        if (!IS_TAGGED(update->version, TAG1)) {

             if (update->version <= txn->rv)
                 break; // success
             continue;
             if (update->version <= txn->rv)
                 break; // success
             continue;


@@ -252,7 +261,7 @@ uint64_t tm_get (txn_t *txn, void *key) {
             continue;
 
         // The update's transaction is still in progress. Access its txn_t.
             continue;
 
         // The update's transaction is still in progress. Access its txn_t.

-        txn_t *writer = (txn_t *)STRIP_TAG(update->version);
+        txn_t *writer = (txn_t *)STRIP_TAG(update->version, TAG1);

         if (writer == txn) // found our own update
             break; // success 
 
         if (writer == txn) // found our own update
             break; // success 
 


@@ -276,49 +285,82 @@ uint64_t tm_get (txn_t *txn, void *key) {
         break; // success
     }
 
         break; // success
     }
 

-    if (EXPECT_FALSE(update == NULL))
-        return DOES_NOT_EXIST;
+    uint64_t value = update->value;

 
     // collect some garbage
 
     // collect some garbage

-    update_rec_t *next = update->next;
-    if (next != NULL) {
-        uint64_t min_active_version = (uint64_t)sl_min_key(active_);
-        if (next->version < min_active_version) {
-            next = SYNC_SWAP(&update->next, NULL);
-            while (next != NULL) {
+    update_t *last = update;
+    update_t *next = update->next;
+    uint64_t min_active = 0;
+    if (IS_TAGGED(next, TAG2)) {
+        next = (update_t *)STRIP_TAG(next, TAG2);
+        min_active = (uint64_t)sl_min_key(active_);
+        if (next->version < min_active) {
+
+            // Skip over aborted versions to verify the chain of updates is old enough for collection
+            update_t *temp = next;
+            while (temp->version == ABORTED_VERSION) {
+                assert(!IS_TAGGED(temp->version, TAG1));
+                update_t *temp = next->next;
+                if (!IS_TAGGED(temp, TAG2))
+                    break;
+                temp = (update_t *)STRIP_TAG(temp, TAG2);
+                if (temp->version >= min_active)
+                    return value;
+                temp = temp->next;
+            }
+
+            // collect <next> and all the update records following it
+            do {
+                next = SYNC_SWAP(&update->next, NULL);
+
+                // if we find ourself in a race just back off and let the other thread take care of it
+                if (next == NULL) 
+                    return value;
+

                 update = next;
                 update = next;

-                next = NULL;
-                if (update->next != NULL) {
-                    next = SYNC_SWAP(&update->next, NULL);
-                }
+                next = next->next;

                 nbd_free(update);
                 nbd_free(update);

-            }
+            } while (IS_TAGGED(next, TAG2));

         }
     }
         }
     }

+
+    // If there is one item left and it is visible by all active transactions we can merge it into the map itself.
+    // There is no need for an update record.
+    if (next == NULL && last == (update_t *)STRIP_TAG(newest_update, TAG2)) {
+        if (min_active == UNDETERMINED_VERSION) {
+            min_active = (uint64_t)sl_min_key(active_);
+        }
+        if (last->version <= min_active) {
+            if (map_cas(txn->map, key, TAG_VALUE(last, TAG2), value) == TAG_VALUE(last, TAG2)) {
+                nbd_defer_free(last);
+            }
+        }
+    } 

     
     

-    return update->value;
+    return value;

 }
 
 void tm_set (txn_t *txn, void *key, uint64_t value) {
 
     // create a new update record
 }
 
 void tm_set (txn_t *txn, void *key, uint64_t value) {
 
     // create a new update record

-    update_rec_t *update = alloc_update_rec();
-    update->type = UPDATE_TYPE_PUT;
+    update_t *update = alloc_update_rec();

     update->value = value;
     update->value = value;

-    update->version = TAG_VALUE((uint64_t)txn);
+    update->version = TAG_VALUE(txn, TAG1);

 
     // push the new update record onto <key>'s update list
 
     // push the new update record onto <key>'s update list

-    uint64_t update_prev;
+    uint64_t old_update;

     do {
     do {

-        update->next = (update_rec_t *) map_get(txn->map, key);
-        update_prev = (uint64_t)update->next;
-    } while (map_cas(txn->map, key, update_prev, (uint64_t)update) != update_prev);
+        old_update = map_get(txn->map, key);
+        update->next = (update_t *)old_update;
+    } while (map_cas(txn->map, key, old_update, TAG_VALUE(update, TAG2)) != old_update);

 
     // add <key> to the write set for commit-time validation
     if (txn->writes_count == txn->writes_size) {
         write_rec_t *w = nbd_malloc(sizeof(write_rec_t) * txn->writes_size * 2);
         memcpy(w, txn->writes, txn->writes_size * sizeof(write_rec_t));
         txn->writes_size *= 2;
 
     // add <key> to the write set for commit-time validation
     if (txn->writes_count == txn->writes_size) {
         write_rec_t *w = nbd_malloc(sizeof(write_rec_t) * txn->writes_size * 2);
         memcpy(w, txn->writes, txn->writes_size * sizeof(write_rec_t));
         txn->writes_size *= 2;

+        nbd_free(txn->writes);
+        txn->writes = w;

     }
     int i = txn->writes_count++;
     txn->writes[i].key = key;
     }
     int i = txn->writes_count++;
     txn->writes[i].key = key;