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mdbx: clarify shrink/grow-related internals.

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This commit is contained in:
Leonid Yuriev 2019-08-12 15:26:26 +03:00
parent 5244c1a9c2
commit bceace7a09
1 changed files with 16 additions and 13 deletions
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29
src/mdbx.c
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@ -2278,8 +2278,7 @@ __cold static int mdbx_mapresize(MDBX_env *env, const pgno_t size_pgno,
* 2) At least on Windows 10 1803 the entire mapped section is unavailable
* for short time during NtExtendSection() or VirtualAlloc() execution.
*
* THEREFORE LOCAL THREADS SUSPENDING IS ALWAYS REQUIRED!
*/
* THEREFORE LOCAL THREADS SUSPENDING IS ALWAYS REQUIRED! */
array_onstack.limit = ARRAY_LENGTH(array_onstack.handles);
array_onstack.count = 0;
suspended = &array_onstack;
@ -2312,7 +2311,7 @@ bailout:
env->me_dbgeo.upper = limit_bytes;
if (env->me_txn) {
mdbx_tassert(env->me_txn, size_pgno >= env->me_txn->mt_next_pgno);
env->me_txn->mt_end_pgno = size_pgno;
env->me_txn->mt_end_pgno = env->me_txn0->mt_end_pgno = size_pgno;
}
#ifdef USE_VALGRIND
if (prev_mapsize != env->me_mapsize || prev_mapaddr != env->me_map) {
@ -3168,7 +3167,7 @@ static int mdbx_txn_renew0(MDBX_txn *txn, unsigned flags) {
STATIC_ASSERT(offsetof(MDBX_lockinfo, mti_readers) % MDBX_CACHELINE_SIZE ==
0);
pgno_t upper_pgno = 0;
pgno_t upper_limit_pgno = 0;
if (flags & MDBX_TXN_RDONLY) {
txn->mt_flags = MDBX_TXN_RDONLY;
MDBX_reader *r = txn->mt_ro_reader;
@ -3235,7 +3234,7 @@ static int mdbx_txn_renew0(MDBX_txn *txn, unsigned flags) {
r = &env->me_lck->mti_readers[slot];
/* Claim the reader slot, carefully since other code
* uses the reader table un-mutexed: First reset the
* slot, next publish it in mtb.mti_numreaders. After
* slot, next publish it in lck->mti_numreaders. After
* that, it is safe for mdbx_env_close() to touch it.
* When it will be closed, we can finally claim it. */
r->mr_pid = 0;
@ -3260,15 +3259,16 @@ static int mdbx_txn_renew0(MDBX_txn *txn, unsigned flags) {
mdbx_jitter4testing(false);
const txnid_t snap = mdbx_meta_txnid_fluid(env, meta);
mdbx_jitter4testing(false);
if (r) {
if (likely(r)) {
r->mr_snapshot_pages = meta->mm_geo.next;
r->mr_txnid = snap;
mdbx_jitter4testing(false);
mdbx_assert(env, r->mr_pid == mdbx_getpid());
mdbx_assert(env, r->mr_tid == mdbx_thread_self());
mdbx_assert(env, r->mr_txnid == snap);
mdbx_flush_noncoherent_cpu_writeback();
mdbx_compiler_barrier();
env->me_lck->mti_readers_refresh_flag = true;
mdbx_flush_noncoherent_cpu_writeback();
}
mdbx_jitter4testing(true);
@ -3276,7 +3276,7 @@ static int mdbx_txn_renew0(MDBX_txn *txn, unsigned flags) {
txn->mt_txnid = snap;
txn->mt_next_pgno = meta->mm_geo.next;
txn->mt_end_pgno = meta->mm_geo.now;
upper_pgno = meta->mm_geo.upper;
upper_limit_pgno = meta->mm_geo.upper;
memcpy(txn->mt_dbs, meta->mm_dbs, CORE_DBS * sizeof(MDBX_db));
txn->mt_canary = meta->mm_canary;
@ -3348,7 +3348,7 @@ static int mdbx_txn_renew0(MDBX_txn *txn, unsigned flags) {
/* Moved to here to avoid a data race in read TXNs */
txn->mt_next_pgno = meta->mm_geo.next;
txn->mt_end_pgno = meta->mm_geo.now;
upper_pgno = meta->mm_geo.upper;
upper_limit_pgno = meta->mm_geo.upper;
}
/* Setup db info */
@ -3369,12 +3369,13 @@ static int mdbx_txn_renew0(MDBX_txn *txn, unsigned flags) {
} else {
const size_t size = pgno2bytes(env, txn->mt_end_pgno);
if (unlikely(size > env->me_mapsize)) {
if (upper_pgno > MAX_PAGENO ||
bytes2pgno(env, pgno2bytes(env, upper_pgno)) != upper_pgno) {
if (upper_limit_pgno > MAX_PAGENO ||
bytes2pgno(env, pgno2bytes(env, upper_limit_pgno)) !=
upper_limit_pgno) {
rc = MDBX_MAP_RESIZED;
goto bailout;
}
rc = mdbx_mapresize(env, txn->mt_end_pgno, upper_pgno);
rc = mdbx_mapresize(env, txn->mt_end_pgno, upper_limit_pgno);
if (rc != MDBX_SUCCESS) {
if (rc == MDBX_RESULT_TRUE)
rc = MDBX_MAP_RESIZED;
@ -5377,7 +5378,9 @@ static int mdbx_sync_locked(MDBX_env *env, unsigned flags,
if ((flags & MDBX_SHRINK_ALLOWED) && pending->mm_geo.shrink &&
pending->mm_geo.now - pending->mm_geo.next >
pending->mm_geo.shrink + backlog_gap) {
const pgno_t largest = mdbx_find_largest(env, pending->mm_geo.next);
const pgno_t largest = mdbx_find_largest(
env, (head->mm_geo.next > pending->mm_geo.next) ? head->mm_geo.next
: pending->mm_geo.next);
if (pending->mm_geo.now > largest &&
pending->mm_geo.now - largest > pending->mm_geo.shrink + backlog_gap) {
const pgno_t aligner =