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Handle loose pages

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Pages that were dirtied and deleted in the same txn should be
reused, instead of consuming freeDB pages.
This commit is contained in:
Howard Chu 2014-06-21 03:30:34 -07:00
parent eebbd22c2f
commit 7cab7b95e2
1 changed files with 70 additions and 5 deletions
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75
libraries/liblmdb/mdb.c
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@ -650,6 +650,7 @@ typedef struct MDB_page {
#define P_DIRTY 0x10 /**< dirty page, also set for #P_SUBP pages */
#define P_LEAF2 0x20 /**< for #MDB_DUPFIXED records */
#define P_SUBP 0x40 /**< for #MDB_DUPSORT sub-pages */
#define P_LOOSE 0x4000 /**< page was dirtied then freed, can be reused */
#define P_KEEP 0x8000 /**< leave this page alone during spill */
/** @} */
uint16_t mp_flags; /**< @ref mdb_page */
@ -1021,6 +1022,7 @@ 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 */
MDB_page *mf_pgloose; /**< Dirty pages that can be reused */
} MDB_pgstate;
/** The database environment. */
@ -1057,6 +1059,7 @@ 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_pgloose me_pgstate.mf_pgloose
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;
@ -1485,7 +1488,6 @@ mdb_page_malloc(MDB_txn *txn, unsigned num)
}
return ret;
}
/** Free a single page.
* Saves single pages to a list, for future reuse.
* (This is not used for multi-page overflow pages.)
@ -1525,6 +1527,23 @@ mdb_dlist_free(MDB_txn *txn)
dl[0].mid = 0;
}
/** Loosen a single page.
* Saves single pages to a list for future reuse
* in this same txn. It has been pulled from the freeDB
* and already resides on the dirty list, but has been
* deleted. Use these pages first before pulling again
* from the freeDB.
*/
static void
mdb_page_loose(MDB_env *env, MDB_page *mp)
{
pgno_t *pp = (pgno_t *)mp->mp_ptrs;
*pp = mp->mp_pgno;
mp->mp_next = env->me_pgloose;
env->me_pgloose = mp;
mp->mp_flags |= P_LOOSE;
}
/** Set or clear P_KEEP in dirty, non-overflow, non-sub pages watched by txn.
* @param[in] mc A cursor handle for the current operation.
* @param[in] pflags Flags of the pages to update:
@ -1573,6 +1592,12 @@ mdb_pages_xkeep(MDB_cursor *mc, unsigned pflags, int all)
break;
}
/* Loose pages shouldn't be spilled */
for (dp = txn->mt_env->me_pgloose; dp; dp=dp->mp_next) {
if ((dp->mp_flags & Mask) == pflags)
dp->mp_flags ^= P_KEEP;
}
if (all) {
/* Mark dirty root pages */
for (i=0; i<txn->mt_numdbs; i++) {
@ -1800,6 +1825,17 @@ mdb_page_alloc(MDB_cursor *mc, int num, MDB_page **mp)
MDB_cursor_op op;
MDB_cursor m2;
/* If there are any loose pages, just use them */
if (num == 1 && env->me_pgloose) {
pgno_t *pp;
np = env->me_pgloose;
env->me_pgloose = np->mp_next;
pp = (pgno_t *)np->mp_ptrs;
np->mp_pgno = *pp;
*mp = np;
return MDB_SUCCESS;
}
*mp = NULL;
/* If our dirty list is already full, we can't do anything */
@ -2661,6 +2697,38 @@ mdb_freelist_save(MDB_txn *txn)
return rc;
}
/* Dispose of loose pages. Usually they will have all
* been used up by the time we get here.
*/
if (env->me_pgloose) {
MDB_page *mp = env->me_pgloose;
pgno_t *pp;
/* Just return them to freeDB */
if (env->me_pghead) {
int i, j;
mop = env->me_pghead;
while(mp) {
pgno_t pg;
pp = (pgno_t *)mp->mp_ptrs;
pg = *pp;
j = mop[0] + 1;
for (i = mop[0]; i && mop[i] < pg; i--)
mop[j--] = mop[i];
mop[j] = pg;
mop[0] += 1;
mp = mp->mp_next;
}
} else {
/* Oh well, they were wasted. Put on freelist */
while(mp) {
pp = (pgno_t *)mp->mp_ptrs;
mdb_midl_append(&txn->mt_free_pgs, *pp);
mp = mp->mp_next;
}
}
env->me_pgloose = NULL;
}
/* MDB_RESERVE cancels meminit in ovpage malloc (when no WRITEMAP) */
clean_limit = (env->me_flags & (MDB_NOMEMINIT|MDB_WRITEMAP))
? SSIZE_MAX : maxfree_1pg;
@ -7261,10 +7329,7 @@ mdb_page_merge(MDB_cursor *csrc, MDB_cursor *cdst)
}
csrc->mc_top++;
rc = mdb_midl_append(&csrc->mc_txn->mt_free_pgs,
csrc->mc_pg[csrc->mc_top]->mp_pgno);
if (rc)
return rc;
mdb_page_loose(csrc->mc_txn->mt_env, csrc->mc_pg[csrc->mc_top]);
if (IS_LEAF(csrc->mc_pg[csrc->mc_top]))
csrc->mc_db->md_leaf_pages--;
else