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lmdb: support for a utterly no-sync mode,

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by combination of MDB_NOSYNC and MDB_MAPASYNC.

Change-Id: I3e2d6c8f044a7522436dab4d0818d4d59b78b78d
This commit is contained in:
Leo Yuriev 2015-09-01 12:04:08 +03:00
parent 030aca6816
commit e7f58da2ac
3 changed files with 26 additions and 5 deletions
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2
lmdb.h
View File

@ -288,6 +288,8 @@ typedef void (MDB_rel_func)(MDB_val *item, void *oldptr, void *newptr, void *rel
#define MDB_COALESCE 0x2000000
/** LIFO policy for reclaiming FreeDB records */
#define MDB_LIFORECLAIM 0x4000000
/** make a steady-sync only on close and explicit env-sync */
#define MDB_UTTERLY_NOSYNC (MDB_NOSYNC|MDB_MAPASYNC)
/** @} */
/** @defgroup mdb_dbi_open Database Flags

27
mdb.c
View File

@ -2341,10 +2341,24 @@ mdb_page_alloc(MDB_cursor *mc, int num, MDB_page **mp, int flags)
MDB_meta* head = mdb_meta_head_w(env);
MDB_meta* tail = mdb_env_meta_flipflop(env, head);
if (META_IS_WEAK(head) && oldest == tail->mm_txnid) {
if (oldest == tail->mm_txnid
&& META_IS_WEAK(head) && !META_IS_WEAK(tail)) {
MDB_meta meta = *head;
/* LY: Here an oom was happened:
* - all pages had allocated;
* - reclaiming was stopped at the last steady-sync;
* - the head-sync is weak.
* Now we need make a sync to resume reclaiming. If both
* MDB_NOSYNC and MDB_MAPASYNC flags are set, then assume that
* utterly no-sync write mode was requested. In such case
* don't make a steady-sync, but only a legacy-mode checkpoint,
* just for resume reclaiming only, not for data consistency. */
int flags = env->me_flags & MDB_WRITEMAP;
if ((env->me_flags & MDB_UTTERLY_NOSYNC) == MDB_UTTERLY_NOSYNC)
flags |= MDB_UTTERLY_NOSYNC;
mdb_assert(env, env->me_sync_pending > 0);
if (mdb_env_sync0(env, env->me_flags & MDB_WRITEMAP, &meta) == MDB_SUCCESS) {
if (mdb_env_sync0(env, flags, &meta) == MDB_SUCCESS) {
txnid_t snap = mdb_find_oldest(env, NULL);
if (snap > oldest)
continue;
@ -4068,8 +4082,13 @@ mdb_env_sync0(MDB_env *env, unsigned flags, MDB_meta *pending)
}
/* LY: step#2 - update meta-page. */
pending->mm_datasync_sign = env->me_sync_pending
? MDB_DATASIGN_WEAK : mdb_meta_sign(pending);
if (env->me_sync_pending == 0) {
pending->mm_datasync_sign = mdb_meta_sign(pending);
} else {
pending->mm_datasync_sign =
(flags & MDB_UTTERLY_NOSYNC) == MDB_UTTERLY_NOSYNC
? MDB_DATASIGN_NONE : MDB_DATASIGN_WEAK;
}
mdb_debug("writing meta page %d for root page %zu",
offset >= env->me_psize, pending->mm_dbs[MAIN_DBI].md_root);
if (env->me_flags & MDB_WRITEMAP) {

2
mdb_chk.c
View File

@ -490,7 +490,7 @@ static void usage(char *prog)
const char* meta_synctype(size_t sign) {
switch(sign) {
case 0:
return "legacy/unknown";
return "no-sync/legacy";
case 1:
return "weak";
default: