More for ITS#7455

Don't memmove freelist entry when chunking it. Just advance the pointer,
now that it's no longer a complex struct. Also just calculate maxfree_1pg
at startup; it's a constant during runtime.

diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index e1f6357c7f09985578e7b2c973f2681c9b5d361a..7bfdfc27bc190faf92b139dc08514e9d6cd16b38 100644 (file)
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -941,12 +941,15 @@ struct MDB_env {
        MDB_dbx         *me_dbxs;               /**< array of static DB info */
        uint16_t        *me_dbflags;    /**< array of flags from MDB_db.md_flags */
        pgno_t          *me_pghead;     /**< old pages reclaimed from freelist */
+       pgno_t          *me_pgfree;     /**< memory to free when dropping me_pghead */
        pthread_key_t   me_txkey;       /**< thread-key for readers */
        MDB_page        *me_dpages;             /**< list of malloc'd blocks for re-use */
        /** IDL of pages that became unused in a write txn */
        MDB_IDL         me_free_pgs;
        /** ID2L of pages that were written during a write txn */
        MDB_ID2         me_dirty_list[MDB_IDL_UM_SIZE];
+       /** Max number of freelist items that can fit in a single overflow page */
+       unsigned int    me_maxfree_1pg;
 #ifdef _WIN32
        HANDLE          me_rmutex;              /* Windows mutexes don't reside in shared mem */
        HANDLE          me_wmutex;
@@ -1337,7 +1340,7 @@ again:
                                if (!mop)
                                        return ENOMEM;
                                txn->mt_env->me_pglast = last;
-                               txn->mt_env->me_pghead = mop;
+                               txn->mt_env->me_pghead = txn->mt_env->me_pgfree = mop;
                                memcpy(mop, idl, MDB_IDL_SIZEOF(idl));
 
 #if MDB_DEBUG > 1
@@ -1422,8 +1425,8 @@ none:
                                                                mop2[k--] = mop[j--];
                                                }
                                                txn->mt_env->me_pglast = last;
-                                               txn->mt_env->me_pghead = mop2;
-                                               free(mop);
+                                               free(txn->mt_env->me_pgfree);
+                                               txn->mt_env->me_pghead = txn->mt_env->me_pgfree = mop2;
                                                mop = mop2;
                                                /* Keep trying to read until we have enough */
                                                if (mop[0] < (unsigned)num) {
@@ -1457,8 +1460,8 @@ none:
                                mop[0]--;
                        }
                        if (MDB_IDL_IS_ZERO(mop)) {
-                               txn->mt_env->me_pghead = NULL;
-                               free(mop);
+                               free(txn->mt_env->me_pgfree);
+                               txn->mt_env->me_pghead = txn->mt_env->me_pgfree = NULL;
                        }
                }
        }
@@ -1931,7 +1934,6 @@ mdb_txn_reset0(MDB_txn *txn)
                if (!(env->me_flags & MDB_ROFS))
                        txn->mt_u.reader->mr_txnid = (txnid_t)-1;
        } else {
-               pgno_t *mop;
                MDB_page *dp;
                unsigned int i;
 
@@ -1971,10 +1973,8 @@ mdb_txn_reset0(MDB_txn *txn)
                                env->me_free_pgs = txn->mt_free_pgs;
                }
 
-               if ((mop = txn->mt_env->me_pghead) != NULL) {
-                       txn->mt_env->me_pghead = NULL;
-                       free(mop);
-               }
+               free(txn->mt_env->me_pgfree);
+               txn->mt_env->me_pghead = txn->mt_env->me_pgfree = NULL;
                txn->mt_env->me_pglast = 0;
 
                env->me_txn = NULL;
@@ -2022,7 +2022,7 @@ mdb_txn_commit(MDB_txn *txn)
        off_t            size;
        MDB_page        *dp;
        MDB_env *env;
-       pgno_t  next, freecnt, maxfree_1pg;
+       pgno_t  next, freecnt;
        txnid_t oldpg_txnid, id;
        MDB_cursor mc;
 
@@ -2148,12 +2148,6 @@ mdb_txn_commit(MDB_txn *txn)
        mdb_cursor_init(&mc, txn, FREE_DBI, NULL);
        oldpg_txnid = id = 0;
        freecnt = 0;
-       /* Preferred max #items per freelist entry, to avoid overflow pages.
-        * Leave room for headers, key (txnid), pagecount (pageno_t), and
-        * FIXME: a bit more in case there is some delimiter I don't know about.
-        */
-       maxfree_1pg = (env->me_psize - (PAGEHDRSZ + NODESIZE + 3*sizeof(MDB_ID)))
-               / sizeof(pgno_t);
 
        /* should only be one record now */
        if (env->me_pghead || env->me_pglast) {
@@ -2246,8 +2240,8 @@ free2:
                i = 2;
                do {
                        orig = mop[0];
-                       if (orig > maxfree_1pg && id > 4)
-                               orig = maxfree_1pg; /* Do not use an overflow page */
+                       if (orig > env->me_maxfree_1pg && id > 4)
+                               orig = env->me_maxfree_1pg; /* Do not use more than 1 page */
                        data.mv_size = (orig + 1) * sizeof(pgno_t);
                        rc = mdb_cursor_put(&mc, &key, &data, MDB_RESERVE);
                        if (rc)
@@ -2262,9 +2256,8 @@ free2:
                if (mop[0] <= orig)
                        break;
                *(pgno_t *)data.mv_data = orig;
-               mop[0] -= orig;
-               memmove(&mop[1], &mop[1 + orig],
-                       mop[0] * sizeof(pgno_t));
+               mop[orig] = mop[0] - orig;
+               env->me_pghead = mop += orig;
                /* Save more oldpages at the previous txnid. */
                assert(env->me_pglast == id && id == oldpg_txnid);
                env->me_pglast = --oldpg_txnid;
@@ -2275,10 +2268,8 @@ free2:
        if (freecnt != txn->mt_free_pgs[0])
                goto free2;
 
-       if (env->me_pghead) {
-               free(env->me_pghead);
-               env->me_pghead = NULL;
-       }
+       free(env->me_pgfree);
+       env->me_pghead = env->me_pgfree = NULL;
 
        if (!MDB_IDL_IS_ZERO(txn->mt_free_pgs)) {
                if (mdb_midl_shrink(&txn->mt_free_pgs))
@@ -2842,6 +2833,7 @@ mdb_env_open2(MDB_env *env)
                return EBUSY;   /* TODO: Make a new MDB_* error code? */
        }
        env->me_psize = meta.mm_psize;
+       env->me_maxfree_1pg = (env->me_psize - PAGEHDRSZ) / sizeof(pgno_t) - 1;
 
        env->me_maxpg = env->me_mapsize / env->me_psize;