ITS#7620: Keep empty IDLs. Tweak mdb_page_alloc().

MDB_env.me_pghead: Don't free it when empty. mdb_ovpage_free()
needs it, but cannot allocate it.
mdb_midl_alloc(): Fill in length=0.
mdb_page_alloc(): Also Skip freeDB if txnid<3, instead of <4,
and consistently DPRINTF consumed IDLs.

diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index 3c8db7eefc6225437fc760a383b95e46d4ffeda9..3a1d39ed84de7b5afa0a1fb7d0c0d91ef57b83f5 100644 (file)
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -928,8 +928,8 @@ typedef struct MDB_xcursor {
 
        /** State of FreeDB old pages, stored in the MDB_env */
 typedef struct MDB_pgstate {
-       txnid_t         mf_pglast;      /**< ID of last old page record we used */
-       pgno_t          *mf_pghead;     /**< old pages reclaimed from freelist */
+       pgno_t          *mf_pghead;     /**< Reclaimed freeDB pages, or NULL before use */
+       txnid_t         mf_pglast;      /**< ID of last used record, or 0 if !mf_pghead */
 } MDB_pgstate;
 
        /** The database environment. */
@@ -1341,8 +1341,10 @@ static int
 mdb_page_alloc(MDB_cursor *mc, int num, MDB_page **mp)
 {
        MDB_txn *txn = mc->mc_txn;
+       MDB_env *env = txn->mt_env;
+       pgno_t pgno = P_INVALID, *mop = env->me_pghead;
+       unsigned mop_len = mop ? mop[0] : 0;
        MDB_page *np;
-       pgno_t pgno = P_INVALID;
        MDB_ID2 mid;
        txnid_t oldest = 0, last;
        int rc;
@@ -1353,13 +1355,11 @@ mdb_page_alloc(MDB_cursor *mc, int num, MDB_page **mp)
        if (txn->mt_dirty_room == 0)
                return MDB_TXN_FULL;
 
-       /* The free list won't have any content at all until txn 2 has
-        * committed. The pages freed by txn 2 will be unreferenced
-        * after txn 3 commits, and so will be safe to re-use in txn 4.
+       /* Pages freed by txn#1 (after allocating but discarding them)
+        * are used when txn#1 is unreferenced, i.e. txn#3.
         */
-       if (txn->mt_txnid > 3) {
-               if (!txn->mt_env->me_pghead &&
-                       txn->mt_dbs[FREE_DBI].md_root != P_INVALID) {
+       if (txn->mt_txnid >= 3) {
+               if (!mop_len && txn->mt_dbs[FREE_DBI].md_root != P_INVALID) {
                        /* See if there's anything in the free DB */
                        MDB_cursor m2;
                        MDB_node *leaf;
@@ -1391,24 +1391,22 @@ again:
                        if (oldest > last) {
                                /* It's usable, grab it.
                                 */
-                               pgno_t *idl, *mop;
+                               pgno_t *idl;
 
                                if (!txn->mt_env->me_pglast) {
                                        mdb_node_read(txn, leaf, &data);
                                }
                                idl = (MDB_ID *) data.mv_data;
-                               /* We might have a zero-length IDL due to freelist growth
-                                * during a prior commit
-                                */
-                               if (!idl[0]) {
-                                       txn->mt_env->me_pglast = last;
-                                       goto again;
+                               mop_len = idl[0];
+                               if (!mop) {
+                                       if (!(env->me_pghead = mop = mdb_midl_alloc(mop_len)))
+                                               return ENOMEM;
+                               } else if (mop_len > mop[-1]) {
+                                       if ((rc = mdb_midl_grow(&env->me_pghead, mop_len)) != 0)
+                                               return rc;
+                                       mop = env->me_pghead;
                                }
-                               mop = mdb_midl_alloc(idl[0]);
-                               if (!mop)
-                                       return ENOMEM;
                                txn->mt_env->me_pglast = last;
-                               txn->mt_env->me_pghead = mop;
                                memcpy(mop, idl, MDB_IDL_SIZEOF(idl));
 
 #if MDB_DEBUG > 1
@@ -1420,11 +1418,15 @@ again:
                                                DPRINTF("IDL %zu", idl[i]);
                                }
 #endif
+                               /* We might have a zero-length IDL due to freelist growth
+                                * during a prior commit
+                                */
+                               if (!mop_len)
+                                       goto again;
                        }
                }
 none:
-               if (txn->mt_env->me_pghead) {
-                       pgno_t *mop = txn->mt_env->me_pghead;
+               if (mop_len) {
                        if (num > 1) {
                                MDB_cursor m2;
                                int retry = 1, readit = 0, n2 = num-1;
@@ -1448,7 +1450,7 @@ none:
 #endif
                                        if (readit) {
                                                MDB_val key, data;
-                                               pgno_t *idl, *mop2;
+                                               pgno_t *idl, old_id, new_id;
 
                                                last = txn->mt_env->me_pglast + 1;
 
@@ -1473,22 +1475,31 @@ none:
                                                if (oldest <= last)
                                                        break;
                                                idl = (MDB_ID *) data.mv_data;
-                                               mop2 = mdb_midl_alloc(idl[0] + mop[0]);
-                                               if (!mop2)
-                                                       return ENOMEM;
+                                               i = idl[0];
+                                               if (mop_len+i > mop[-1]) {
+                                                       if ((rc = mdb_midl_grow(&env->me_pghead, i)) != 0)
+                                                               return rc;
+                                                       mop = env->me_pghead;
+                                               }
+#if MDB_DEBUG > 1
+                                               DPRINTF("IDL read txn %zu root %zu num %u",
+                                                       last, txn->mt_dbs[FREE_DBI].md_root, i);
+                                               for (k = i; k; k--)
+                                                       DPRINTF("IDL %zu", idl[k]);
+#endif
                                                /* merge in sorted order */
-                                               i = idl[0]; j = mop[0]; mop2[0] = k = i+j;
+                                               j = mop_len;
+                                               k = mop_len += i;
                                                mop[0] = P_INVALID;
-                                               while (i>0  || j>0) {
-                                                       if (i && idl[i] < mop[j])
-                                                               mop2[k--] = idl[i--];
-                                                       else
-                                                               mop2[k--] = mop[j--];
+                                               old_id = mop[j];
+                                               while (i) {
+                                                       new_id = idl[i--];
+                                                       for (; old_id < new_id; old_id = mop[--j])
+                                                               mop[k--] = old_id;
+                                                       mop[k--] = new_id;
                                                }
+                                               mop[0] = mop_len;
                                                txn->mt_env->me_pglast = last;
-                                               mdb_midl_free(txn->mt_env->me_pghead);
-                                               txn->mt_env->me_pghead = mop2;
-                                               mop = mop2;
                                                /* Keep trying to read until we have enough */
                                                if (mop[0] < (unsigned)num) {
                                                        continue;
@@ -1519,10 +1530,6 @@ none:
                                pgno = MDB_IDL_LAST(mop);
                                mop[0]--;
                        }
-                       if (MDB_IDL_IS_ZERO(mop)) {
-                               mdb_midl_free(txn->mt_env->me_pghead);
-                               txn->mt_env->me_pghead = NULL;
-                       }
                }
        }
 
@@ -1966,7 +1973,6 @@ mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
                txn->mt_toggle = parent->mt_toggle;
                txn->mt_dirty_room = parent->mt_dirty_room;
                txn->mt_u.dirty_list[0].mid = 0;
-               txn->mt_free_pgs[0] = 0;
                txn->mt_next_pgno = parent->mt_next_pgno;
                parent->mt_child = txn;
                txn->mt_parent = parent;
@@ -2138,7 +2144,7 @@ mdb_freelist_save(MDB_txn *txn)
 
        mdb_cursor_init(&mc, txn, FREE_DBI, NULL);
 
-       if (env->me_pghead || env->me_pglast) {
+       if (env->me_pghead) {
                /* Make sure first page of freeDB is touched and on freelist */
                rc = mdb_page_search(&mc, NULL, MDB_PS_MODIFY);
                if (rc && rc != MDB_NOTFOUND)

diff --git a/libraries/liblmdb/midl.c b/libraries/liblmdb/midl.c
index d2617c61e45841719ebb953eb74bafb42748d7d2..00df385cdc83363234f728434829c8eae26663e4 100644 (file)
--- a/libraries/liblmdb/midl.c
+++ b/libraries/liblmdb/midl.c
@@ -104,8 +104,10 @@ int mdb_midl_insert( MDB_IDL ids, MDB_ID id )
 MDB_IDL mdb_midl_alloc(int num)
 {
        MDB_IDL ids = malloc((num+2) * sizeof(MDB_ID));
-       if (ids)
+       if (ids) {
                *ids++ = num;
+               *ids = 0;
+       }
        return ids;
 }