Don't alloc in cursor_push/pop

diff --git a/libraries/libmdb/mdb.c b/libraries/libmdb/mdb.c
index 85535f89e29f740f09bc75c8ea84e3cd9fb94e08..0ca8ffd8bda25d2878cc2e2ce35d2d91c818d239 100644 (file)
--- a/libraries/libmdb/mdb.c
+++ b/libraries/libmdb/mdb.c
@@ -29,7 +29,6 @@
  */
 #include <sys/types.h>
 #include <sys/stat.h>
-#include <sys/queue.h>
 #include <sys/param.h>
 #include <sys/uio.h>
 #include <sys/mman.h>
@@ -231,25 +230,19 @@ static MDB_dpage *mdb_alloc_page(MDB_txn *txn, MDB_page *parent, unsigned int pa
 static int             mdb_touch(MDB_txn *txn, MDB_pageparent *mp);
 
 typedef struct MDB_ppage {                                     /* ordered list of pages */
-       SLIST_ENTRY(MDB_ppage)   mp_entry;
        MDB_page                *mp_page;
        unsigned int    mp_ki;          /* cursor index on page */
 } MDB_ppage;
-SLIST_HEAD(page_stack, MDB_ppage);
 
-/* FIXME: tree depth is mostly bounded, we should just
- * use a fixed array and avoid malloc/pointer chasing
- */
-#define CURSOR_EMPTY(c)                 SLIST_EMPTY(&(c)->mc_stack)
-#define CURSOR_TOP(c)           SLIST_FIRST(&(c)->mc_stack)
-#define CURSOR_POP(c)           SLIST_REMOVE_HEAD(&(c)->mc_stack, mp_entry)
-#define CURSOR_PUSH(c,p)        SLIST_INSERT_HEAD(&(c)->mc_stack, p, mp_entry)
+#define CURSOR_TOP(c)           (&(c)->mc_stack[(c)->mc_snum-1])
+#define CURSOR_PARENT(c)        (&(c)->mc_stack[(c)->mc_snum-2])
 
 struct MDB_xcursor;
 
 struct MDB_cursor {
        MDB_txn         *mc_txn;
-       struct page_stack        mc_stack;              /* stack of parent pages */
+       MDB_ppage       mc_stack[32];           /* stack of parent pages */
+       unsigned int    mc_snum;                /* number of pushed pages */
        MDB_dbi         mc_dbi;
        short           mc_initialized; /* 1 if initialized */
        short           mc_eof;         /* 1 if end is reached */
@@ -1542,12 +1535,12 @@ cursor_pop_page(MDB_cursor *cursor)
 {
        MDB_ppage       *top;
 
-       top = CURSOR_TOP(cursor);
-       CURSOR_POP(cursor);
-
-       DPRINTF("popped page %lu off cursor %p", top->mp_page->mp_pgno, (void *) cursor);
+       if (cursor->mc_snum) {
+               top = CURSOR_TOP(cursor);
+               cursor->mc_snum--;
 
-       free(top);
+               DPRINTF("popped page %lu off cursor %p", top->mp_page->mp_pgno, (void *) cursor);
+       }
 }
 
 static MDB_ppage *
@@ -1557,10 +1550,9 @@ cursor_push_page(MDB_cursor *cursor, MDB_page *mp)
 
        DPRINTF("pushing page %lu on cursor %p", mp->mp_pgno, (void *) cursor);
 
-       if ((ppage = calloc(1, sizeof(MDB_ppage))) == NULL)
-               return NULL;
+       ppage = &cursor->mc_stack[cursor->mc_snum++];
        ppage->mp_page = mp;
-       CURSOR_PUSH(cursor, ppage);
+       ppage->mp_ki = 0;
        return ppage;
 }
 
@@ -1794,13 +1786,13 @@ mdb_sibling(MDB_cursor *cursor, int move_right)
 {
        int              rc;
        MDB_node        *indx;
-       MDB_ppage       *parent, *top;
+       MDB_ppage       *parent;
        MDB_page        *mp;
 
-       top = CURSOR_TOP(cursor);
-       if ((parent = SLIST_NEXT(top, mp_entry)) == NULL) {
+       if (cursor->mc_snum < 2) {
                return MDB_NOTFOUND;            /* root has no siblings */
        }
+       parent = CURSOR_PARENT(cursor);
 
        DPRINTF("parent page is page %lu, index %u",
            parent->mp_page->mp_pgno, parent->mp_ki);
@@ -1979,8 +1971,7 @@ mdb_cursor_set(MDB_cursor *cursor, MDB_val *key, MDB_val *data,
        assert(key);
        assert(key->mv_size > 0);
 
-       while (CURSOR_TOP(cursor) != NULL)
-               cursor_pop_page(cursor);
+       cursor->mc_snum = 0;
 
        rc = mdb_search_page(cursor->mc_txn, cursor->mc_dbi, key, cursor, 0, &mpp);
        if (rc != MDB_SUCCESS)
@@ -2054,8 +2045,7 @@ mdb_cursor_first(MDB_cursor *cursor, MDB_val *key, MDB_val *data)
        MDB_pageparent  mpp;
        MDB_node        *leaf;
 
-       while (CURSOR_TOP(cursor) != NULL)
-               cursor_pop_page(cursor);
+       cursor->mc_snum = 0;
 
        rc = mdb_search_page(cursor->mc_txn, cursor->mc_dbi, NULL, cursor, 0, &mpp);
        if (rc != MDB_SUCCESS)
@@ -2089,8 +2079,7 @@ mdb_cursor_last(MDB_cursor *cursor, MDB_val *key, MDB_val *data)
        MDB_node        *leaf;
        MDB_val lkey;
 
-       while (CURSOR_TOP(cursor) != NULL)
-               cursor_pop_page(cursor);
+       cursor->mc_snum = 0;
 
        lkey.mv_size = MAXKEYSIZE+1;
        lkey.mv_data = NULL;
@@ -2387,7 +2376,7 @@ mdb_xcursor_init0(MDB_txn *txn, MDB_dbi dbi, MDB_xcursor *mx)
        mx->mx_dbxs[dbn+1].md_dirty = 0;
        mx->mx_txn.mt_numdbs = dbn+2;
 
-       SLIST_INIT(&mx->mx_cursor.mc_stack);
+       mx->mx_cursor.mc_snum = 0;
        mx->mx_cursor.mc_txn = &mx->mx_txn;
        mx->mx_cursor.mc_dbi = dbn+1;
 }
@@ -2442,7 +2431,6 @@ mdb_cursor_open(MDB_txn *txn, MDB_dbi dbi, MDB_cursor **ret)
                size += sizeof(MDB_xcursor);
 
        if ((cursor = calloc(1, size)) != NULL) {
-               SLIST_INIT(&cursor->mc_stack);
                cursor->mc_dbi = dbi;
                cursor->mc_txn = txn;
                if (txn->mt_dbs[dbi].md_flags & MDB_DUPSORT) {
@@ -2480,13 +2468,6 @@ void
 mdb_cursor_close(MDB_cursor *cursor)
 {
        if (cursor != NULL) {
-               while(!CURSOR_EMPTY(cursor))
-                       cursor_pop_page(cursor);
-               if (cursor->mc_txn->mt_dbs[cursor->mc_dbi].md_flags & MDB_DUPSORT) {
-                       while(!CURSOR_EMPTY(&cursor->mc_xcursor->mx_cursor))
-                               cursor_pop_page(&cursor->mc_xcursor->mx_cursor);
-               }
-
                free(cursor);
        }
 }
@@ -2852,24 +2833,21 @@ mdb_del(MDB_txn *txn, MDB_dbi dbi,
                                unsigned int i;
 
                                cursor_pop_page(&mx.mx_cursor);
-                               top = CURSOR_TOP(&mx.mx_cursor);
-                               if (top != NULL) {
-                                       parent = SLIST_NEXT(top, mp_entry);
-                                       while (parent != NULL) {
+                               if (mx.mx_cursor.mc_snum) {
+                                       top = CURSOR_TOP(&mx.mx_cursor);
+                                       while (mx.mx_cursor.mc_snum > 1) {
+                                               parent = CURSOR_PARENT(&mx.mx_cursor);
                                                for (i=0; i<NUMKEYS(top->mp_page); i++) {
                                                        ni = NODEPTR(top->mp_page, i);
                                                        mdb_midl_insert(txn->mt_free_pgs, ni->mn_pgno);
                                                }
-                                               if (parent) {
-                                                       parent->mp_ki++;
-                                                       if (parent->mp_ki >= NUMKEYS(parent->mp_page)) {
-                                                               cursor_pop_page(&mx.mx_cursor);
-                                                               top = CURSOR_TOP(&mx.mx_cursor);
-                                                               parent = SLIST_NEXT(top, mp_entry);
-                                                       } else {
-                                                               ni = NODEPTR(parent->mp_page, parent->mp_ki);
-                                                               top->mp_page = mdb_get_page(&mx.mx_txn, ni->mn_pgno);
-                                                       }
+                                               parent->mp_ki++;
+                                               if (parent->mp_ki >= NUMKEYS(parent->mp_page)) {
+                                                       cursor_pop_page(&mx.mx_cursor);
+                                                       top = parent;
+                                               } else {
+                                                       ni = NODEPTR(parent->mp_page, parent->mp_ki);
+                                                       top->mp_page = mdb_get_page(&mx.mx_txn, ni->mn_pgno);
                                                }
                                        }
                                }