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Simplify mdb_page_alloc().

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Merge if() branches. Restore retry=500 when MDB_PARANOID, for clarity.
This commit is contained in:
Hallvard Furuseth 2013-06-20 07:41:35 +02:00
parent 4a9ee2cb72
commit c6f9323b3d
1 changed files with 106 additions and 183 deletions
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227
libraries/liblmdb/mdb.c
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@ -1340,14 +1340,27 @@ mdb_find_oldest(MDB_txn *txn)
static int static int
mdb_page_alloc(MDB_cursor *mc, int num, MDB_page **mp) mdb_page_alloc(MDB_cursor *mc, int num, MDB_page **mp)
{ {
#ifdef MDB_PARANOID /* Seems like we can ignore this now */
/* Get at most <Max_retries> more freeDB records once me_pghead
* has enough pages. If not enough, use new pages from the map.
* If <Paranoid> and mc is updating the freeDB, only get new
* records if me_pghead is empty. Then the freelist cannot play
* catch-up with itself by growing while trying to save it.
*/
enum { Paranoid = 1, Max_retries = 500 };
#else
enum { Paranoid = 0, Max_retries = INT_MAX /*infinite*/ };
#endif
int rc, n2 = num-1, retry = Max_retries;
MDB_txn *txn = mc->mc_txn; MDB_txn *txn = mc->mc_txn;
MDB_env *env = txn->mt_env; MDB_env *env = txn->mt_env;
pgno_t pgno = P_INVALID, *mop = env->me_pghead; pgno_t pgno, *mop = env->me_pghead;
unsigned mop_len = mop ? mop[0] : 0; unsigned mop_len = mop ? mop[0] : 0;
MDB_page *np; MDB_page *np;
MDB_ID2 mid; MDB_ID2 mid;
txnid_t oldest = 0, last; txnid_t oldest = 0, last;
int rc; MDB_cursor_op op;
MDB_cursor m2;
*mp = NULL; *mp = NULL;
@ -1355,117 +1368,52 @@ mdb_page_alloc(MDB_cursor *mc, int num, MDB_page **mp)
if (txn->mt_dirty_room == 0) if (txn->mt_dirty_room == 0)
return MDB_TXN_FULL; return MDB_TXN_FULL;
/* Pages freed by txn#1 (after allocating but discarding them) for (op = MDB_FIRST;; op = MDB_NEXT) {
* are used when txn#1 is unreferenced, i.e. txn#3.
*/
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;
MDB_val data;
txnid_t *kptr;
mdb_cursor_init(&m2, txn, FREE_DBI, NULL);
if (!txn->mt_env->me_pglast) {
mdb_page_search(&m2, NULL, 0);
leaf = NODEPTR(m2.mc_pg[m2.mc_top], 0);
kptr = (txnid_t *)NODEKEY(leaf);
last = *kptr;
} else {
MDB_val key;
again:
last = txn->mt_env->me_pglast + 1;
leaf = NULL;
key.mv_data = &last;
key.mv_size = sizeof(last);
rc = mdb_cursor_set(&m2, &key, &data, MDB_SET_RANGE, NULL);
if (rc)
goto none;
last = *(txnid_t *)key.mv_data;
}
if (!oldest)
oldest = mdb_find_oldest(txn);
if (oldest > last) {
/* It's usable, grab it.
*/
pgno_t *idl;
if (!txn->mt_env->me_pglast) {
mdb_node_read(txn, leaf, &data);
}
idl = (MDB_ID *) data.mv_data;
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;
}
txn->mt_env->me_pglast = last;
memcpy(mop, idl, MDB_IDL_SIZEOF(idl));
#if MDB_DEBUG > 1
{
unsigned int i;
DPRINTF("IDL read txn %zu root %zu num %zu",
last, txn->mt_dbs[FREE_DBI].md_root, idl[0]);
for (i = idl[0]; i; i--)
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 (mop_len) {
if (num > 1) {
MDB_cursor m2;
int retry = 1, readit = 0, n2 = num-1;
unsigned int i, j, k; unsigned int i, j, k;
/* If current list is too short, must fetch more and coalesce */
if (mop[0] < (unsigned)num)
readit = 1;
mdb_cursor_init(&m2, txn, FREE_DBI, NULL);
do {
#ifdef MDB_PARANOID /* Seems like we can ignore this now */
/* If on freelist, don't try to read more. If what we have
* right now isn't enough just use new pages.
* TODO: get all of this working. Many circular dependencies...
*/
if (mc->mc_dbi == FREE_DBI) {
retry = 0;
readit = 0;
}
#endif
if (readit) {
MDB_val key, data; MDB_val key, data;
MDB_node *leaf;
pgno_t *idl, old_id, new_id; pgno_t *idl, old_id, new_id;
last = txn->mt_env->me_pglast + 1; /* Seek a big enough contiguous page range. Prefer
* pages at the tail, just truncating the list.
/* We haven't hit the readers list yet? */ */
if (!oldest) { if (mop_len >= (unsigned)num) {
oldest = mdb_find_oldest(txn); i = mop_len;
do {
pgno = mop[i];
if (mop[i-n2] == pgno+n2) {
mop[0] = mop_len -= num;
/* Move any stragglers down */
for (j = i-n2; j <= mop_len; )
mop[j++] = mop[++i];
goto search_done;
}
} while (--i >= (unsigned)num);
if (Max_retries < INT_MAX && --retry < 0)
break;
} }
/* There's nothing we can use on the freelist */ if (op == MDB_FIRST) { /* 1st iteration */
if (oldest - last < 1) /* Prepare to fetch more and coalesce */
oldest = mdb_find_oldest(txn);
last = env->me_pglast;
mdb_cursor_init(&m2, txn, FREE_DBI, NULL);
if (last) {
op = MDB_SET_RANGE;
key.mv_data = &last; /* will loop up last+1 */
key.mv_size = sizeof(last);
}
if (Paranoid && mc->mc_dbi == FREE_DBI)
retry = -1;
}
if (Paranoid && retry < 0 && mop_len)
break; break;
key.mv_data = &last; last++;
key.mv_size = sizeof(last); /* Do not fetch more if the record will be too recent */
rc = mdb_cursor_set(&m2,&key,&data,MDB_SET_RANGE,NULL); if (oldest <= last)
break;
rc = mdb_cursor_get(&m2, &key, NULL, op);
if (rc) { if (rc) {
if (rc == MDB_NOTFOUND) if (rc == MDB_NOTFOUND)
break; break;
@ -1474,23 +1422,32 @@ none:
last = *(txnid_t*)key.mv_data; last = *(txnid_t*)key.mv_data;
if (oldest <= last) if (oldest <= last)
break; break;
np = m2.mc_pg[m2.mc_top];
leaf = NODEPTR(np, m2.mc_ki[m2.mc_top]);
if ((rc = mdb_node_read(txn, leaf, &data)) != MDB_SUCCESS)
return rc;
idl = (MDB_ID *) data.mv_data; idl = (MDB_ID *) data.mv_data;
i = idl[0]; i = idl[0];
if (mop_len+i > mop[-1]) { if (!mop) {
if (!(env->me_pghead = mop = mdb_midl_alloc(i)))
return ENOMEM;
} else if (mop_len+i > mop[-1]) {
if ((rc = mdb_midl_grow(&env->me_pghead, i)) != 0) if ((rc = mdb_midl_grow(&env->me_pghead, i)) != 0)
return rc; return rc;
mop = env->me_pghead; mop = env->me_pghead;
} }
env->me_pglast = last;
#if MDB_DEBUG > 1 #if MDB_DEBUG > 1
DPRINTF("IDL read txn %zu root %zu num %u", DPRINTF("IDL read txn %zu root %zu num %u",
last, txn->mt_dbs[FREE_DBI].md_root, i); last, txn->mt_dbs[FREE_DBI].md_root, i);
for (k = i; k; k--) for (k = i; k; k--)
DPRINTF("IDL %zu", idl[k]); DPRINTF("IDL %zu", idl[k]);
#endif #endif
/* merge in sorted order */ /* Merge in descending sorted order */
j = mop_len; j = mop_len;
k = mop_len += i; k = mop_len += i;
mop[0] = P_INVALID; mop[0] = (pgno_t)-1;
old_id = mop[j]; old_id = mop[j];
while (i) { while (i) {
new_id = idl[i--]; new_id = idl[i--];
@ -1499,67 +1456,33 @@ none:
mop[k--] = new_id; mop[k--] = new_id;
} }
mop[0] = mop_len; mop[0] = mop_len;
txn->mt_env->me_pglast = last;
/* Keep trying to read until we have enough */
if (mop[0] < (unsigned)num) {
continue;
}
} }
/* current list has enough pages, but are they contiguous? */ /* Use new pages from the map when nothing suitable in the freeDB */
for (i=mop[0]; i>=(unsigned)num; i--) { pgno = P_INVALID;
if (mop[i-n2] == mop[i] + n2) { if (txn->mt_next_pgno + num >= env->me_maxpg) {
pgno = mop[i];
i -= n2;
/* move any stragglers down */
for (j=i+num; j<=mop[0]; j++)
mop[i++] = mop[j];
mop[0] -= num;
break;
}
}
/* Stop if we succeeded, or no retries */
if (!retry || pgno != P_INVALID)
break;
readit = 1;
} while (1);
} else {
/* peel pages off tail, so we only have to truncate the list */
pgno = MDB_IDL_LAST(mop);
mop[0]--;
}
}
}
if (pgno == P_INVALID) {
/* DB size is maxed out */
if (txn->mt_next_pgno + num >= txn->mt_env->me_maxpg) {
DPUTS("DB size maxed out"); DPUTS("DB size maxed out");
return MDB_MAP_FULL; return MDB_MAP_FULL;
} }
}
if (txn->mt_env->me_flags & MDB_WRITEMAP) { search_done:
if (env->me_flags & MDB_WRITEMAP) {
if (pgno == P_INVALID) { if (pgno == P_INVALID) {
pgno = txn->mt_next_pgno; pgno = txn->mt_next_pgno;
txn->mt_next_pgno += num; txn->mt_next_pgno += num;
} }
np = (MDB_page *)(txn->mt_env->me_map + txn->mt_env->me_psize * pgno); np = (MDB_page *)(env->me_map + env->me_psize * pgno);
np->mp_pgno = pgno;
} else { } else {
if (!(np = mdb_page_malloc(mc, num))) if (!(np = mdb_page_malloc(mc, num)))
return ENOMEM; return ENOMEM;
if (pgno == P_INVALID) { if (pgno == P_INVALID) {
np->mp_pgno = txn->mt_next_pgno; pgno = txn->mt_next_pgno;
txn->mt_next_pgno += num; txn->mt_next_pgno += num;
} else {
np->mp_pgno = pgno;
} }
} }
mid.mid = np->mp_pgno; mid.mid = np->mp_pgno = pgno;
mid.mptr = np; mid.mptr = np;
if (txn->mt_env->me_flags & MDB_WRITEMAP) { if (env->me_flags & MDB_WRITEMAP) {
mdb_mid2l_append(txn->mt_u.dirty_list, &mid); mdb_mid2l_append(txn->mt_u.dirty_list, &mid);
} else { } else {
mdb_mid2l_insert(txn->mt_u.dirty_list, &mid); mdb_mid2l_insert(txn->mt_u.dirty_list, &mid);