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Remember oldest reader txnid

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Don't walk the readers table unless we really need to.
This commit is contained in:
Howard Chu 2014-09-09 19:40:05 +01:00
parent 4d02c741b1
commit 29fd241fad
1 changed files with 22 additions and 5 deletions
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27
libraries/liblmdb/mdb.c
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@ -1083,6 +1083,7 @@ typedef struct MDB_xcursor {
typedef struct MDB_pgstate {
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 */
txnid_t mf_pgoldest; /**< ID of oldest reader last time we looked */
} MDB_pgstate;
/** The database environment. */
@ -1121,6 +1122,7 @@ struct MDB_env {
MDB_pgstate me_pgstate; /**< state of old pages from freeDB */
# define me_pglast me_pgstate.mf_pglast
# define me_pghead me_pgstate.mf_pghead
# define me_pgoldest me_pgstate.mf_pgoldest
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;
@ -1956,6 +1958,7 @@ mdb_page_alloc(MDB_cursor *mc, int num, MDB_page **mp)
txnid_t oldest = 0, last;
MDB_cursor_op op;
MDB_cursor m2;
int found_old = 0;
/* If there are any loose pages, just use them */
if (num == 1 && txn->mt_loose_pgs) {
@ -1997,8 +2000,8 @@ mdb_page_alloc(MDB_cursor *mc, int num, MDB_page **mp)
if (op == MDB_FIRST) { /* 1st iteration */
/* Prepare to fetch more and coalesce */
oldest = mdb_find_oldest(txn);
last = env->me_pglast;
oldest = env->me_pgoldest;
mdb_cursor_init(&m2, txn, FREE_DBI, NULL);
if (last) {
op = MDB_SET_RANGE;
@ -2013,8 +2016,15 @@ mdb_page_alloc(MDB_cursor *mc, int num, MDB_page **mp)
last++;
/* Do not fetch more if the record will be too recent */
if (oldest <= last)
break;
if (oldest <= last) {
if (!found_old) {
oldest = mdb_find_oldest(txn);
env->me_pgoldest = oldest;
found_old = 1;
}
if (oldest <= last)
break;
}
rc = mdb_cursor_get(&m2, &key, NULL, op);
if (rc) {
if (rc == MDB_NOTFOUND)
@ -2022,8 +2032,15 @@ mdb_page_alloc(MDB_cursor *mc, int num, MDB_page **mp)
goto fail;
}
last = *(txnid_t*)key.mv_data;
if (oldest <= last)
break;
if (oldest <= last) {
if (!found_old) {
oldest = mdb_find_oldest(txn);
env->me_pgoldest = oldest;
found_old = 1;
}
if (oldest <= last)
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)