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Remove unnecessary transaction initialization 

`ReadYourWritesTransaction` has memory allocated before being passed to
the main thread. This allows both threads to continue to access the
transaction object. Currently, the transaction gets allocated and
initialized on the foreign thread, and then re-initialized on the main
thread. This causes a bunch of extra, unnecessary work for each
`ReadYourWritesTransaction` where the temporary object gets destructed.

The fix is to only allocate memory for the `ReadYourWritesTransaction`
on the foreign thread, and then initialize it once on the main thread.
This commit is contained in:
Lukas Joswiak 2022-06-10 16:53:19 -07:00
parent 0bb02f6415
commit 3b3ef49d40
2 changed files with 17 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
fdbclient/ISingleThreadTransaction.cpp
View File

@ -26,9 +26,14 @@
ISingleThreadTransaction* ISingleThreadTransaction::allocateOnForeignThread(Type type) {
if (type == Type::RYW) {
auto tr = new ReadYourWritesTransaction;
// We only want to allocate memory for the transaction, not initialize
// the object, so use operator new instead of new. The RYWTransaction
// will get initialized on the main thread.
auto tr =
(ReadYourWritesTransaction*)ReadYourWritesTransaction::operator new(sizeof(ReadYourWritesTransaction));
return tr;
} else if (type == Type::SIMPLE_CONFIG) {
// Configuration transaction objects expect to be initialized.
auto tr = new SimpleConfigTransaction;
return tr;
} else if (type == Type::PAXOS_CONFIG) {

14
fdbclient/ThreadSafeTransaction.cpp
View File

@ -190,12 +190,20 @@ ThreadSafeTransaction::ThreadSafeTransaction(DatabaseContext* cx,
auto tr = this->tr = ISingleThreadTransaction::allocateOnForeignThread(type);
// No deferred error -- if the construction of the RYW transaction fails, we have no where to put it
onMainThreadVoid(
[tr, cx, tenant]() {
[tr, cx, type, tenant]() {
cx->addref();
if (tenant.present()) {
tr->construct(Database(cx), tenant.get());
if (type == ISingleThreadTransaction::Type::RYW) {
new (tr) ReadYourWritesTransaction(Database(cx), tenant.get());
} else {
tr->construct(Database(cx), tenant.get());
}
} else {
tr->construct(Database(cx));
if (type == ISingleThreadTransaction::Type::RYW) {
new (tr) ReadYourWritesTransaction(Database(cx));
} else {
tr->construct(Database(cx));
}
}
},
nullptr);