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dcsctp: Use std::deque for outstanding_data

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A std::map is a fairly inefficient data structure. Accessing an item
is O(log(N)), but as every item is a separate allocation, iterating it
and searching for items is not very kind to the data caches.

As the outstanding data is a contiguous list (no gaps) where you only
append to the end and remove from the front, use a std::deque instead.

Bug: webrtc:15699
Co-authored-by: Daniel Collins <dpcollins@google.com>
Change-Id: I1f5fe97d06204c75b2b9553856af24e50f2ce715
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/329422
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#41310}
This commit is contained in:
Victor Boivie 2023-12-01 20:47:05 +01:00 committed by WebRTC LUCI CQ
parent fe66dda733
commit 9abc4865a4
2 changed files with 109 additions and 76 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

174
net/dcsctp/tx/outstanding_data.cc
View File

@ -19,6 +19,7 @@
#include "net/dcsctp/common/math.h"
#include "net/dcsctp/common/sequence_numbers.h"
#include "net/dcsctp/public/types.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
namespace dcsctp {
@ -86,7 +87,9 @@ bool OutstandingData::IsConsistent() const {
to_be_fast_retransmitted_.end());
std::set<UnwrappedTSN> actual_combined_to_be_retransmitted;
for (const auto& [tsn, item] : outstanding_data_) {
UnwrappedTSN tsn = last_cumulative_tsn_ack_;
for (const Item& item : outstanding_data_) {
tsn.Increment();
if (item.is_outstanding()) {
actual_outstanding_bytes += GetSerializedChunkSize(item.data());
++actual_outstanding_items;
@ -103,22 +106,22 @@ bool OutstandingData::IsConsistent() const {
}
void OutstandingData::AckChunk(AckInfo& ack_info,
std::map<UnwrappedTSN, Item>::iterator iter) {
if (!iter->second.is_acked()) {
size_t serialized_size = GetSerializedChunkSize(iter->second.data());
UnwrappedTSN tsn,
Item& item) {
if (!item.is_acked()) {
size_t serialized_size = GetSerializedChunkSize(item.data());
ack_info.bytes_acked += serialized_size;
if (iter->second.is_outstanding()) {
if (item.is_outstanding()) {
outstanding_bytes_ -= serialized_size;
--outstanding_items_;
}
if (iter->second.should_be_retransmitted()) {
RTC_DCHECK(to_be_fast_retransmitted_.find(iter->first) ==
if (item.should_be_retransmitted()) {
RTC_DCHECK(to_be_fast_retransmitted_.find(tsn) ==
to_be_fast_retransmitted_.end());
to_be_retransmitted_.erase(iter->first);
to_be_retransmitted_.erase(tsn);
}
iter->second.Ack();
ack_info.highest_tsn_acked =
std::max(ack_info.highest_tsn_acked, iter->first);
item.Ack();
ack_info.highest_tsn_acked = std::max(ack_info.highest_tsn_acked, tsn);
}
}
@ -141,24 +144,43 @@ OutstandingData::AckInfo OutstandingData::HandleSack(
return ack_info;
}
OutstandingData::Item& OutstandingData::GetItem(UnwrappedTSN tsn) {
RTC_DCHECK(tsn > last_cumulative_tsn_ack_);
RTC_DCHECK(tsn < next_tsn());
int index = UnwrappedTSN::Difference(tsn, last_cumulative_tsn_ack_) - 1;
RTC_DCHECK(index >= 0);
RTC_DCHECK(index < static_cast<int>(outstanding_data_.size()));
return outstanding_data_[index];
}
const OutstandingData::Item& OutstandingData::GetItem(UnwrappedTSN tsn) const {
RTC_DCHECK(tsn > last_cumulative_tsn_ack_);
RTC_DCHECK(tsn < next_tsn());
int index = UnwrappedTSN::Difference(tsn, last_cumulative_tsn_ack_) - 1;
RTC_DCHECK(index >= 0);
RTC_DCHECK(index < static_cast<int>(outstanding_data_.size()));
return outstanding_data_[index];
}
void OutstandingData::RemoveAcked(UnwrappedTSN cumulative_tsn_ack,
AckInfo& ack_info) {
auto first_unacked = outstanding_data_.upper_bound(cumulative_tsn_ack);
for (auto iter = outstanding_data_.begin(); iter != first_unacked; ++iter) {
AckChunk(ack_info, iter);
if (iter->second.lifecycle_id().IsSet()) {
RTC_DCHECK(iter->second.data().is_end);
if (iter->second.is_abandoned()) {
ack_info.abandoned_lifecycle_ids.push_back(iter->second.lifecycle_id());
while (!outstanding_data_.empty() &&
last_cumulative_tsn_ack_ < cumulative_tsn_ack) {
UnwrappedTSN tsn = last_cumulative_tsn_ack_.next_value();
Item& item = outstanding_data_.front();
AckChunk(ack_info, tsn, item);
if (item.lifecycle_id().IsSet()) {
RTC_DCHECK(item.data().is_end);
if (item.is_abandoned()) {
ack_info.abandoned_lifecycle_ids.push_back(item.lifecycle_id());
} else {
ack_info.acked_lifecycle_ids.push_back(iter->second.lifecycle_id());
ack_info.acked_lifecycle_ids.push_back(item.lifecycle_id());
}
}
outstanding_data_.pop_front();
last_cumulative_tsn_ack_.Increment();
}
outstanding_data_.erase(outstanding_data_.begin(), first_unacked);
last_cumulative_tsn_ack_ = cumulative_tsn_ack;
stream_reset_breakpoint_tsns_.erase(stream_reset_breakpoint_tsns_.begin(),
stream_reset_breakpoint_tsns_.upper_bound(
cumulative_tsn_ack.next_value()));
@ -174,12 +196,13 @@ void OutstandingData::AckGapBlocks(
// handled differently.
for (auto& block : gap_ack_blocks) {
auto start = outstanding_data_.lower_bound(
UnwrappedTSN::AddTo(cumulative_tsn_ack, block.start));
auto end = outstanding_data_.upper_bound(
UnwrappedTSN::AddTo(cumulative_tsn_ack, block.end));
for (auto iter = start; iter != end; ++iter) {
AckChunk(ack_info, iter);
UnwrappedTSN start = UnwrappedTSN::AddTo(cumulative_tsn_ack, block.start);
UnwrappedTSN end = UnwrappedTSN::AddTo(cumulative_tsn_ack, block.end);
for (UnwrappedTSN tsn = start; tsn <= end; tsn = tsn.next_value()) {
if (tsn > last_cumulative_tsn_ack_ && tsn < next_tsn()) {
Item& item = GetItem(tsn);
AckChunk(ack_info, tsn, item);
}
}
}
}
@ -214,13 +237,13 @@ void OutstandingData::NackBetweenAckBlocks(
for (auto& block : gap_ack_blocks) {
UnwrappedTSN cur_block_first_acked =
UnwrappedTSN::AddTo(cumulative_tsn_ack, block.start);
for (auto iter = outstanding_data_.upper_bound(prev_block_last_acked);
iter != outstanding_data_.lower_bound(cur_block_first_acked); ++iter) {
if (iter->first <= max_tsn_to_nack) {
ack_info.has_packet_loss |=
NackItem(iter->first, iter->second, /*retransmit_now=*/false,
/*do_fast_retransmit=*/!is_in_fast_recovery);
}
for (UnwrappedTSN tsn = prev_block_last_acked.next_value();
tsn < cur_block_first_acked && tsn <= max_tsn_to_nack;
tsn = tsn.next_value()) {
Item& item = GetItem(tsn);
ack_info.has_packet_loss |=
NackItem(tsn, item, /*retransmit_now=*/false,
/*do_fast_retransmit=*/!is_in_fast_recovery);
}
prev_block_last_acked = UnwrappedTSN::AddTo(cumulative_tsn_ack, block.end);
}
@ -275,14 +298,10 @@ void OutstandingData::AbandonAllFor(const Item& item) {
Data::IsBeginning(false), Data::IsEnd(true),
item.data().is_unordered);
UnwrappedTSN tsn = next_tsn();
Item& added_item =
outstanding_data_
.emplace(std::piecewise_construct, std::forward_as_tuple(tsn),
std::forward_as_tuple(
item.message_id(), std::move(message_end),
Timestamp::Zero(), MaxRetransmits(0),
Timestamp::PlusInfinity(), LifecycleId::NotSet()))
.first->second;
Item& added_item = outstanding_data_.emplace_back(
item.message_id(), std::move(message_end), Timestamp::Zero(),
MaxRetransmits(0), Timestamp::PlusInfinity(), LifecycleId::NotSet());
// The added chunk shouldn't be included in `outstanding_bytes`, so set it
// as acked.
added_item.Ack();
@ -290,7 +309,9 @@ void OutstandingData::AbandonAllFor(const Item& item) {
<< *tsn.Wrap();
}
for (auto& [tsn, other] : outstanding_data_) {
UnwrappedTSN tsn = last_cumulative_tsn_ack_;
for (Item& other : outstanding_data_) {
tsn.Increment();
if (!other.is_abandoned() &&
other.data().stream_id == item.data().stream_id &&
other.message_id() == item.message_id()) {
@ -312,9 +333,7 @@ std::vector<std::pair<TSN, Data>> OutstandingData::ExtractChunksThatCanFit(
for (auto it = chunks.begin(); it != chunks.end();) {
UnwrappedTSN tsn = *it;
auto elem = outstanding_data_.find(tsn);
RTC_DCHECK(elem != outstanding_data_.end());
Item& item = elem->second;
Item& item = GetItem(tsn);
RTC_DCHECK(item.should_be_retransmitted());
RTC_DCHECK(!item.is_outstanding());
RTC_DCHECK(!item.is_abandoned());
@ -368,7 +387,9 @@ std::vector<std::pair<TSN, Data>> OutstandingData::GetChunksToBeRetransmitted(
}
void OutstandingData::ExpireOutstandingChunks(Timestamp now) {
for (const auto& [tsn, item] : outstanding_data_) {
UnwrappedTSN tsn = last_cumulative_tsn_ack_;
for (const Item& item : outstanding_data_) {
tsn.Increment();
// Chunks that are nacked can be expired. Care should be taken not to expire
// unacked (in-flight) chunks as they might have been received, but the SACK
// is either delayed or in-flight and may be received later.
@ -404,20 +425,17 @@ absl::optional<UnwrappedTSN> OutstandingData::Insert(
outstanding_bytes_ += chunk_size;
++outstanding_items_;
UnwrappedTSN tsn = next_tsn();
auto it = outstanding_data_
.emplace(std::piecewise_construct, std::forward_as_tuple(tsn),
std::forward_as_tuple(message_id, data.Clone(),
time_sent, max_retransmissions,
expires_at, lifecycle_id))
.first;
Item& item = outstanding_data_.emplace_back(message_id, data.Clone(),
time_sent, max_retransmissions,
expires_at, lifecycle_id);
if (it->second.has_expired(time_sent)) {
if (item.has_expired(time_sent)) {
// No need to send it - it was expired when it was in the send
// queue.
RTC_DLOG(LS_VERBOSE) << "Marking freshly produced chunk "
<< *it->first.Wrap() << " and message "
<< *it->second.data().mid << " as expired";
AbandonAllFor(it->second);
RTC_DLOG(LS_VERBOSE) << "Marking freshly produced chunk " << *tsn.Wrap()
<< " and message " << *item.data().mid
<< " as expired";
AbandonAllFor(item);
RTC_DCHECK(IsConsistent());
return absl::nullopt;
}
@ -427,7 +445,9 @@ absl::optional<UnwrappedTSN> OutstandingData::Insert(
}
void OutstandingData::NackAll() {
for (auto& [tsn, item] : outstanding_data_) {
UnwrappedTSN tsn = last_cumulative_tsn_ack_;
for (Item& item : outstanding_data_) {
tsn.Increment();
if (!item.is_acked()) {
NackItem(tsn, item, /*retransmit_now=*/true,
/*do_fast_retransmit=*/false);
@ -438,14 +458,16 @@ void OutstandingData::NackAll() {
webrtc::TimeDelta OutstandingData::MeasureRTT(Timestamp now,
UnwrappedTSN tsn) const {
auto it = outstanding_data_.find(tsn);
if (it != outstanding_data_.end() && !it->second.has_been_retransmitted()) {
// https://tools.ietf.org/html/rfc4960#section-6.3.1
// "Karn's algorithm: RTT measurements MUST NOT be made using
// packets that were retransmitted (and thus for which it is ambiguous
// whether the reply was for the first instance of the chunk or for a
// later instance)"
return now - it->second.time_sent();
if (tsn > last_cumulative_tsn_ack_ && tsn < next_tsn()) {
const Item& item = GetItem(tsn);
if (!item.has_been_retransmitted()) {
// https://tools.ietf.org/html/rfc4960#section-6.3.1
// "Karn's algorithm: RTT measurements MUST NOT be made using
// packets that were retransmitted (and thus for which it is ambiguous
// whether the reply was for the first instance of the chunk or for a
// later instance)"
return now - item.time_sent();
}
}
return webrtc::TimeDelta::PlusInfinity();
}
@ -454,7 +476,9 @@ std::vector<std::pair<TSN, OutstandingData::State>>
OutstandingData::GetChunkStatesForTesting() const {
std::vector<std::pair<TSN, State>> states;
states.emplace_back(last_cumulative_tsn_ack_.Wrap(), State::kAcked);
for (const auto& [tsn, item] : outstanding_data_) {
UnwrappedTSN tsn = last_cumulative_tsn_ack_;
for (const Item& item : outstanding_data_) {
tsn.Increment();
State state;
if (item.is_abandoned()) {
state = State::kAbandoned;
@ -475,9 +499,7 @@ OutstandingData::GetChunkStatesForTesting() const {
bool OutstandingData::ShouldSendForwardTsn() const {
if (!outstanding_data_.empty()) {
auto it = outstanding_data_.begin();
return it->first == last_cumulative_tsn_ack_.next_value() &&
it->second.is_abandoned();
return outstanding_data_.front().is_abandoned();
}
return false;
}
@ -486,7 +508,9 @@ ForwardTsnChunk OutstandingData::CreateForwardTsn() const {
std::map<StreamID, SSN> skipped_per_ordered_stream;
UnwrappedTSN new_cumulative_ack = last_cumulative_tsn_ack_;
for (const auto& [tsn, item] : outstanding_data_) {
UnwrappedTSN tsn = last_cumulative_tsn_ack_;
for (const Item& item : outstanding_data_) {
tsn.Increment();
if (stream_reset_breakpoint_tsns_.contains(tsn) ||
(tsn != new_cumulative_ack.next_value()) || !item.is_abandoned()) {
break;
@ -510,7 +534,9 @@ IForwardTsnChunk OutstandingData::CreateIForwardTsn() const {
std::map<std::pair<IsUnordered, StreamID>, MID> skipped_per_stream;
UnwrappedTSN new_cumulative_ack = last_cumulative_tsn_ack_;
for (const auto& [tsn, item] : outstanding_data_) {
UnwrappedTSN tsn = last_cumulative_tsn_ack_;
for (const Item& item : outstanding_data_) {
tsn.Increment();
if (stream_reset_breakpoint_tsns_.contains(tsn) ||
(tsn != new_cumulative_ack.next_value()) || !item.is_abandoned()) {
break;

11
net/dcsctp/tx/outstanding_data.h
View File

@ -10,6 +10,7 @@
#ifndef NET_DCSCTP_TX_OUTSTANDING_DATA_H_
#define NET_DCSCTP_TX_OUTSTANDING_DATA_H_
#include <deque>
#include <map>
#include <set>
#include <utility>
@ -290,6 +291,9 @@ class OutstandingData {
// Returns how large a chunk will be, serialized, carrying the data
size_t GetSerializedChunkSize(const Data& data) const;
Item& GetItem(UnwrappedTSN tsn);
const Item& GetItem(UnwrappedTSN tsn) const;
// Given a `cumulative_tsn_ack` from an incoming SACK, will remove those items
// in the retransmission queue up until this value and will update `ack_info`
// by setting `bytes_acked_by_cumulative_tsn_ack`.
@ -313,7 +317,7 @@ class OutstandingData {
// Process the acknowledgement of the chunk referenced by `iter` and updates
// state in `ack_info` and the object's state.
void AckChunk(AckInfo& ack_info, std::map<UnwrappedTSN, Item>::iterator iter);
void AckChunk(AckInfo& ack_info, UnwrappedTSN tsn, Item& item);
// Helper method to process an incoming nack of an item and perform the
// correct operations given the action indicated when nacking an item (e.g.
@ -346,7 +350,10 @@ class OutstandingData {
// Callback when to discard items from the send queue.
std::function<bool(StreamID, OutgoingMessageId)> discard_from_send_queue_;
std::map<UnwrappedTSN, Item> outstanding_data_;
// Outstanding items. If non-empty, the first element has
// `TSN=last_cumulative_tsn_ack_ + 1` and the following items are in strict
// increasing TSN order. The last item has `TSN=highest_outstanding_tsn()`.
std::deque<Item> outstanding_data_;
// The number of bytes that are in-flight (sent but not yet acked or nacked).
size_t outstanding_bytes_ = 0;
// The number of DATA chunks that are in-flight (sent but not yet acked or