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Less aggressive page_spill

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spilling all possible pages is a waste because the majority will be
needed again. Just do 1/8th of the dirty list instead.
This commit is contained in:
Howard Chu 2013-08-22 18:51:48 -07:00
parent c22a7d98ec
commit 7b1db13050
1 changed files with 50 additions and 3 deletions
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53
libraries/liblmdb/mdb.c
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@ -1429,7 +1429,7 @@ mdb_page_spill(MDB_cursor *m0, MDB_val *key, MDB_val *data)
MDB_txn *txn = m0->mc_txn;
MDB_page *dp;
MDB_ID2L dl = txn->mt_u.dirty_list;
unsigned int i, j;
unsigned int i, j, k, need;
int rc, level;
if (m0->mc_flags & C_SUB)
@ -1444,6 +1444,7 @@ mdb_page_spill(MDB_cursor *m0, MDB_val *key, MDB_val *data)
if (key)
i += (LEAFSIZE(key, data) + txn->mt_env->me_psize) / txn->mt_env->me_psize;
i += i; /* double it for good measure */
need = i;
if (txn->mt_dirty_room > i)
return MDB_SUCCESS;
@ -1470,8 +1471,21 @@ mdb_page_spill(MDB_cursor *m0, MDB_val *key, MDB_val *data)
/* Preserve pages used by cursors */
mdb_cursorpages_mark(m0, P_DIRTY);
/* Less aggressive spill - we originally spilled the entire dirty list,
* with a few exceptions for cursor pages and DB root pages. But this
* turns out to be a lot of wasted effort because in a large txn many
* of those pages will need to be used again. So now we spill only 1/8th
* of the dirty pages. Testing revealed this to be a good tradeoff,
* better than 1/2, 1/4, or 1/10.
*/
k = 0;
need *= 100;
if (need < MDB_IDL_UM_MAX / 8)
need = MDB_IDL_UM_MAX / 8;
/* Save the page IDs of all the pages we're flushing */
for (i=1; i<=dl[0].mid; i++) {
/* flush from the tail forward, this saves a lot of shifting later on. */
for (i=dl[0].mid; i>0; i--) {
dp = dl[i].mptr;
if (dp->mp_flags & P_KEEP)
continue;
@ -1494,13 +1508,46 @@ mdb_page_spill(MDB_cursor *m0, MDB_val *key, MDB_val *data)
}
if ((rc = mdb_midl_append(&txn->mt_spill_pgs, dl[i].mid)))
goto done;
k++;
if (k > need)
break;
}
mdb_midl_sort(txn->mt_spill_pgs);
rc = mdb_page_flush(txn);
/* Since we're only doing the tail 1/8th of the dirty list,
* fake a dirty list to reflect this.
*/
{
MDB_ID2 old;
k = dl[0].mid - i + 1;
old = dl[i-1];
dl[i-1].mid = k;
txn->mt_u.dirty_list = &dl[i-1];
rc = mdb_page_flush(txn);
/* reset back to the real list */
dl[0].mid -= k;
dl[0].mid += dl[i-1].mid;
dl[i-1] = old;
txn->mt_u.dirty_list = dl;
}
mdb_cursorpages_mark(m0, P_DIRTY|P_KEEP);
/* Reset any dirty root pages we kept that page_flush didn't see */
for (i=0; i<txn->mt_numdbs; i++) {
if (txn->mt_dbflags[i] & DB_DIRTY) {
pgno_t pgno = txn->mt_dbs[i].md_root;
if (pgno == P_INVALID)
continue;
if ((rc = mdb_page_get(txn, pgno, &dp, &level)) != MDB_SUCCESS)
goto done;
if (dp->mp_flags & P_KEEP)
dp->mp_flags ^= P_KEEP;
}
}
done:
if (rc == 0) {
if (txn->mt_parent) {