Add a fastpath for message reassembly that avoids map insertion
Change-Id: I50204915f4857f22e091fb9d88b4111e40d64227
Bug: webrtc:15724
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/331340
Commit-Queue: Daniel Collins <dpcollins@google.com>
Reviewed-by: Victor Boivie <boivie@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#41379}
diff --git a/net/dcsctp/rx/traditional_reassembly_streams.cc b/net/dcsctp/rx/traditional_reassembly_streams.cc
index dce6c90..c94691f 100644
--- a/net/dcsctp/rx/traditional_reassembly_streams.cc
+++ b/net/dcsctp/rx/traditional_reassembly_streams.cc
@@ -86,6 +86,11 @@
int TraditionalReassemblyStreams::UnorderedStream::Add(UnwrappedTSN tsn,
Data data) {
+ if (data.is_beginning && data.is_end) {
+ // Fastpath for already assembled chunks.
+ AssembleMessage(tsn, std::move(data));
+ return 0;
+ }
int queued_bytes = data.size();
auto [it, inserted] = chunks_.emplace(tsn, std::move(data));
if (!inserted) {
@@ -124,12 +129,7 @@
if (count == 1) {
// Fast path - zero-copy
- const Data& data = start->second;
- size_t payload_size = start->second.size();
- UnwrappedTSN tsns[1] = {start->first};
- DcSctpMessage message(data.stream_id, data.ppid, std::move(data.payload));
- parent_.on_assembled_message_(tsns, std::move(message));
- return payload_size;
+ return AssembleMessage(start->first, std::move(start->second));
}
// Slow path - will need to concatenate the payload.
@@ -155,6 +155,17 @@
return payload_size;
}
+size_t TraditionalReassemblyStreams::StreamBase::AssembleMessage(
+ UnwrappedTSN tsn,
+ Data data) {
+ // Fast path - zero-copy
+ size_t payload_size = data.size();
+ UnwrappedTSN tsns[1] = {tsn};
+ DcSctpMessage message(data.stream_id, data.ppid, std::move(data.payload));
+ parent_.on_assembled_message_(tsns, std::move(message));
+ return payload_size;
+}
+
size_t TraditionalReassemblyStreams::UnorderedStream::EraseTo(
UnwrappedTSN tsn) {
auto end_iter = chunks_.upper_bound(tsn);
@@ -202,20 +213,40 @@
return assembled_bytes;
}
+size_t
+TraditionalReassemblyStreams::OrderedStream::TryToAssembleMessagesFastpath(
+ UnwrappedSSN ssn,
+ UnwrappedTSN tsn,
+ Data data) {
+ RTC_DCHECK(ssn == next_ssn_);
+ size_t assembled_bytes = 0;
+ if (data.is_beginning && data.is_end) {
+ assembled_bytes += AssembleMessage(tsn, std::move(data));
+ next_ssn_.Increment();
+ } else {
+ size_t queued_bytes = data.size();
+ auto [iter, inserted] = chunks_by_ssn_[ssn].emplace(tsn, std::move(data));
+ if (!inserted) {
+ // Not actually assembled, but deduplicated meaning queued size doesn't
+ // include this message.
+ return queued_bytes;
+ }
+ }
+ return assembled_bytes + TryToAssembleMessages();
+}
+
int TraditionalReassemblyStreams::OrderedStream::Add(UnwrappedTSN tsn,
Data data) {
int queued_bytes = data.size();
-
UnwrappedSSN ssn = ssn_unwrapper_.Unwrap(data.ssn);
- auto [unused, inserted] = chunks_by_ssn_[ssn].emplace(tsn, std::move(data));
+ if (ssn == next_ssn_) {
+ return queued_bytes -
+ TryToAssembleMessagesFastpath(ssn, tsn, std::move(data));
+ }
+ auto [iter, inserted] = chunks_by_ssn_[ssn].emplace(tsn, std::move(data));
if (!inserted) {
return 0;
}
-
- if (ssn == next_ssn_) {
- queued_bytes -= TryToAssembleMessages();
- }
-
return queued_bytes;
}
diff --git a/net/dcsctp/rx/traditional_reassembly_streams.h b/net/dcsctp/rx/traditional_reassembly_streams.h
index d355c59..9214a9b 100644
--- a/net/dcsctp/rx/traditional_reassembly_streams.h
+++ b/net/dcsctp/rx/traditional_reassembly_streams.h
@@ -55,6 +55,7 @@
: parent_(*parent) {}
size_t AssembleMessage(ChunkMap::iterator start, ChunkMap::iterator end);
+ size_t AssembleMessage(UnwrappedTSN tsn, Data data);
TraditionalReassemblyStreams& parent_;
};
@@ -101,6 +102,11 @@
// Returns the number of bytes assembled if a message was assembled.
size_t TryToAssembleMessage();
size_t TryToAssembleMessages();
+ // Same as above but when inserting the first complete message avoid
+ // insertion into the map.
+ size_t TryToAssembleMessagesFastpath(UnwrappedSSN ssn,
+ UnwrappedTSN tsn,
+ Data data);
// This must be an ordered container to be able to iterate in SSN order.
std::map<UnwrappedSSN, ChunkMap> chunks_by_ssn_;
UnwrappedSSN::Unwrapper ssn_unwrapper_;
