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mdbx: refine/simplify mdbx_find_oldest().

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Simplify b6f14780e381300beaf782fa74252b791aae082e
This commit is contained in:
Leo Yuriev 2017-10-27 15:43:06 +03:00
parent 1a27e40701
commit d4bf0a3332
1 changed files with 12 additions and 29 deletions
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41
src/mdbx.c
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@ -1564,43 +1564,25 @@ static txnid_t mdbx_find_oldest(MDBX_txn *txn) {
return edge;
const uint32_t nothing_changed = MDBX_STRING_TETRAD("None");
const uint32_t no_readers = MDBX_STRING_TETRAD("Void");
const uint32_t snap_readers_refresh_flag = lck->mti_readers_refresh_flag;
mdbx_jitter4testing(false);
if (snap_readers_refresh_flag == nothing_changed)
return last_oldest;
if (snap_readers_refresh_flag == no_readers) {
mdbx_notice("no-reareds, update oldest %" PRIaTXN " -> %" PRIaTXN,
last_oldest, edge);
mdbx_tassert(txn, edge >= lck->mti_oldest);
return lck->mti_oldest = edge;
}
unsigned pending = 0;
txnid_t oldest = edge;
while (true) {
lck->mti_readers_refresh_flag = nothing_changed;
mdbx_coherent_barrier();
const unsigned snap_nreaders = lck->mti_numreaders;
for (unsigned i = 0; i < snap_nreaders; ++i) {
if (lck->mti_readers[i].mr_pid) {
/* mdbx_jitter4testing(true); */
const txnid_t snap = lck->mti_readers[i].mr_txnid;
pending += (snap < ~(txnid_t)0);
if (oldest > snap && last_oldest <= /* ignore pending updates */ snap) {
oldest = snap;
if (oldest == last_oldest)
return oldest;
}
lck->mti_readers_refresh_flag = nothing_changed;
mdbx_coherent_barrier();
const unsigned snap_nreaders = lck->mti_numreaders;
for (unsigned i = 0; i < snap_nreaders; ++i) {
if (lck->mti_readers[i].mr_pid) {
/* mdbx_jitter4testing(true); */
const txnid_t snap = lck->mti_readers[i].mr_txnid;
if (oldest > snap && last_oldest <= /* ignore pending updates */ snap) {
oldest = snap;
if (oldest == last_oldest)
return oldest;
}
}
if (unlikely(lck->mti_readers_refresh_flag != nothing_changed))
continue;
if (pending > 0 ||
mdbx_atomic_compare_and_swap32(&lck->mti_readers_refresh_flag,
nothing_changed, no_readers))
break;
}
if (oldest != last_oldest) {
@ -3762,6 +3744,7 @@ int mdbx_txn_commit(MDBX_txn *txn) {
}
if (unlikely(rc != MDBX_SUCCESS))
goto fail;
env->me_lck->mti_readers_refresh_flag = false;
end_mode = MDBX_END_COMMITTED | MDBX_END_UPDATE | MDBX_END_EOTDONE;
done: