Highlevel lib: allow hash tables to shrink

Allow hash tables to shrink as well as grow.

diff --git a/ChangeLog b/ChangeLog
index 1a9e60262065818db1ec1b2c86be2dc2ac2b24f4..58108077da90a01982ad75251a0f96d2cf4f83b7 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2010-12-16  Miklos Szeredi <miklos@szeredi.hu>
+
+       * Highlevel lib: allow hash tables to shrink
+
 2010-12-13  Miklos Szeredi <miklos@szeredi.hu>
 
        * Highlevel lib: use dynamically resized hash table for looking up

diff --git a/lib/fuse.c b/lib/fuse.c
index 5b0a9ac4739115c3b47670b1136015e781c24067..33196f3df54f294f63c411a0cb225acc2f594537 100644 (file)
--- a/lib/fuse.c
+++ b/lib/fuse.c
@@ -39,6 +39,8 @@
 #define FUSE_UNKNOWN_INO 0xffffffff
 #define OFFSET_MAX 0x7fffffffffffffffLL
 
+#define NODE_TABLE_MIN_SIZE 8192
+
 struct fuse_config {
        unsigned int uid;
        unsigned int gid;
@@ -304,6 +306,48 @@ static void free_node(struct node *node)
        free(node);
 }
 
+static void node_table_reduce(struct node_table *t)
+{
+       size_t newsize = t->size / 2;
+       void *newarray;
+
+       if (newsize < NODE_TABLE_MIN_SIZE)
+               return;
+
+       newarray = realloc(t->array, sizeof(struct node *) * newsize);
+       if (newarray != NULL)
+               t->array = newarray;
+
+       t->size = newsize;
+       t->split = t->size / 2;
+}
+
+static void remerge_id(struct fuse *f)
+{
+       struct node_table *t = &f->id_table;
+       int iter;
+
+       if (t->split == 0)
+               node_table_reduce(t);
+
+       for (iter = 4; t->split > 0 && iter; iter--) {
+               struct node **upper;
+
+               t->split--;
+               upper = &t->array[t->split + t->size / 2];
+               if (*upper) {
+                       struct node **nodep;
+
+                       for (nodep = &t->array[t->split]; *nodep;
+                            nodep = &(*nodep)->id_next);
+
+                       *nodep = *upper;
+                       *upper = NULL;
+                       break;
+               }
+       }
+}
+
 static void unhash_id(struct fuse *f, struct node *node)
 {
        struct node **nodep = &f->id_table.array[id_hash(f, node->nodeid)];
@@ -312,6 +356,9 @@ static void unhash_id(struct fuse *f, struct node *node)
                if (*nodep == node) {
                        *nodep = node->id_next;
                        f->id_table.use--;
+
+                       if(f->id_table.use < f->id_table.size / 4)
+                               remerge_id(f);
                        return;
                }
 }
@@ -392,6 +439,32 @@ static size_t name_hash(struct fuse *f, fuse_ino_t parent,
 
 static void unref_node(struct fuse *f, struct node *node);
 
+static void remerge_name(struct fuse *f)
+{
+       struct node_table *t = &f->name_table;
+       int iter;
+
+       if (t->split == 0)
+               node_table_reduce(t);
+
+       for (iter = 4; t->split > 0 && iter; iter--) {
+               struct node **upper;
+
+               t->split--;
+               upper = &t->array[t->split + t->size / 2];
+               if (*upper) {
+                       struct node **nodep;
+
+                       for (nodep = &t->array[t->split]; *nodep;
+                            nodep = &(*nodep)->name_next);
+
+                       *nodep = *upper;
+                       *upper = NULL;
+                       break;
+               }
+       }
+}
+
 static void unhash_name(struct fuse *f, struct node *node)
 {
        if (node->name) {
@@ -407,6 +480,9 @@ static void unhash_name(struct fuse *f, struct node *node)
                                node->name = NULL;
                                node->parent = NULL;
                                f->name_table.use--;
+
+                               if (f->name_table.use < f->name_table.size / 4)
+                                       remerge_name(f);
                                return;
                        }
                fprintf(stderr,
@@ -3910,7 +3986,7 @@ struct fuse_fs *fuse_fs_new(const struct fuse_operations *op, size_t op_size,
 
 static int node_table_init(struct node_table *t)
 {
-       t->size = 8192;
+       t->size = NODE_TABLE_MIN_SIZE;
        t->array = (struct node **) calloc(1, sizeof(struct node *) * t->size);
        if (t->array == NULL) {
                fprintf(stderr, "fuse: memory allocation failed\n");