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tcp: Performance optimized TcpTxBuffer

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This commit is contained in:
Natale Patriciello
2017-02-03 14:02:50 +01:00
parent e32e1bf1af
commit 4ff71229b8
2 changed files with 125 additions and 21 deletions
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134
src/internet/model/tcp-tx-buffer.cc
View File

@@ -54,9 +54,7 @@ TcpTxItem::TcpTxItem (const TcpTxItem &other)
void
TcpTxItem::Print (std::ostream &os) const
{
NS_LOG_FUNCTION (this);
bool comma = false;
os << "pkt pointer: " << m_packet;
if (m_lost)
{
@@ -178,6 +176,10 @@ TcpTxBuffer::SetHeadSequence (const SequenceNumber32& seq)
{
NS_LOG_FUNCTION (this << seq);
m_firstByteSeq = seq;
// if you change the head with data already sent, something bad will happen
NS_ASSERT (m_sentList.size () == 0);
m_highestSack = std::make_pair (m_sentList.end (), SequenceNumber32 (0));
}
bool
@@ -298,8 +300,11 @@ TcpTxBuffer::GetNewSegment (uint32_t numBytes)
SequenceNumber32 startOfAppList = m_firstByteSeq + m_sentSize;
bool listEdited = false;
TcpTxItem *item = GetPacketFromList (m_appList, startOfAppList,
numBytes, startOfAppList);
numBytes, startOfAppList, &listEdited);
(void) listEdited;
// Move item from AppList to SentList (should be the first, not too complex)
PacketList::iterator it = std::find (m_appList.begin (), m_appList.end (), item);
@@ -319,9 +324,43 @@ TcpTxBuffer::GetTransmittedSegment (uint32_t numBytes, const SequenceNumber32 &s
NS_ASSERT (seq >= m_firstByteSeq);
NS_ASSERT (numBytes <= m_sentSize);
return GetPacketFromList (m_sentList, m_firstByteSeq, numBytes, seq);
bool listEdited = false;
TcpTxItem *item = GetPacketFromList (m_sentList, m_firstByteSeq, numBytes, seq, &listEdited);
if (listEdited && m_highestSack.second >= m_firstByteSeq)
{
m_highestSack = GetHighestSacked ();
}
return item;
}
std::pair <TcpTxBuffer::PacketList::const_iterator, SequenceNumber32>
TcpTxBuffer::GetHighestSacked () const
{
NS_LOG_FUNCTION (this);
PacketList::const_iterator it;
std::pair <TcpTxBuffer::PacketList::const_iterator, SequenceNumber32> ret;
SequenceNumber32 beginOfCurrentPacket = m_firstByteSeq;
ret = std::make_pair (m_sentList.end (), SequenceNumber32 (0));
for (it = m_sentList.begin (); it != m_sentList.end (); ++it)
{
const TcpTxItem *item = *it;
if (item->m_sacked)
{
ret = std::make_pair (it, beginOfCurrentPacket);
}
beginOfCurrentPacket += item->m_packet->GetSize ();
}
return ret;
}
void
TcpTxBuffer::SplitItems (TcpTxItem &t1, TcpTxItem &t2, uint32_t size) const
{
@@ -338,7 +377,8 @@ TcpTxBuffer::SplitItems (TcpTxItem &t1, TcpTxItem &t2, uint32_t size) const
TcpTxItem*
TcpTxBuffer::GetPacketFromList (PacketList &list, const SequenceNumber32 &listStartFrom,
uint32_t numBytes, const SequenceNumber32 &seq) const
uint32_t numBytes, const SequenceNumber32 &seq,
bool *listEdited) const
{
NS_LOG_FUNCTION (this << numBytes << seq);
@@ -407,8 +447,9 @@ TcpTxBuffer::GetPacketFromList (PacketList &list, const SequenceNumber32 &listSt
// insert firstPart before currentItem
list.insert (it, firstPart);
*listEdited = true;
return GetPacketFromList (list, listStartFrom, numBytes, seq);
return GetPacketFromList (list, listStartFrom, numBytes, seq, listEdited);
}
else
{
@@ -452,8 +493,9 @@ TcpTxBuffer::GetPacketFromList (PacketList &list, const SequenceNumber32 &listSt
MergeItems (*previous, *currentItem);
delete currentItem;
*listEdited = true;
return GetPacketFromList (list, listStartFrom, numBytes, seq);
return GetPacketFromList (list, listStartFrom, numBytes, seq, listEdited);
}
}
else if (numBytes < currentPacket->GetSize ())
@@ -465,6 +507,7 @@ TcpTxBuffer::GetPacketFromList (PacketList &list, const SequenceNumber32 &listSt
// insert firstPart before currentItem
list.insert (it, firstPart);
*listEdited = true;
return firstPart;
}
@@ -493,7 +536,9 @@ TcpTxBuffer::GetPacketFromList (PacketList &list, const SequenceNumber32 &listSt
delete next;
return GetPacketFromList (list, listStartFrom, numBytes, seq);
*listEdited = true;
return GetPacketFromList (list, listStartFrom, numBytes, seq, listEdited);
}
}
@@ -602,6 +647,11 @@ TcpTxBuffer::DiscardUpTo (const SequenceNumber32& seq)
}
}
if (m_highestSack.second <= m_firstByteSeq)
{
m_highestSack = std::make_pair (m_sentList.end (), SequenceNumber32 (0));
}
NS_LOG_DEBUG ("Discarded up to " << seq);
NS_LOG_LOGIC ("Buffer status after discarding data " << *this);
NS_ASSERT (m_firstByteSeq >= seq);
@@ -648,6 +698,11 @@ TcpTxBuffer::Update (const TcpOptionSack::SackList &list)
", checking sentList for block " << beginOfCurrentPacket <<
";" << beginOfCurrentPacket + current->GetSize () <<
"], found in the sackboard, sacking");
if (m_highestSack.second <= beginOfCurrentPacket + current->GetSize ())
{
PacketList::iterator new_it = item_it;
m_highestSack = std::make_pair (++new_it, beginOfCurrentPacket+current->GetSize ());
}
}
modified = true;
}
@@ -667,6 +722,8 @@ TcpTxBuffer::Update (const TcpOptionSack::SackList &list)
}
}
NS_ASSERT ((*(m_sentList.begin ()))->m_sacked == false);
return modified;
}
@@ -682,29 +739,46 @@ TcpTxBuffer::IsLost (const SequenceNumber32 &seq, const PacketList::const_iterat
Ptr<const Packet> current;
SequenceNumber32 beginOfCurrentPacket = seq;
NS_LOG_INFO ("Checking if seq=" << seq << " is lost from the buffer ");
if ((*segment)->m_lost == true)
{
NS_LOG_INFO ("seq=" << seq << " is lost because of lost flag");
return true;
}
if ((*segment)->m_sacked == true)
{
NS_LOG_INFO ("seq=" << seq << " is not lost because of sacked flag");
return false;
}
// From RFC 6675:
// > The routine returns true when either dupThresh discontiguous SACKed
// > sequences have arrived above 'seq' or more than (dupThresh - 1) * SMSS bytes
// > with sequence numbers greater than 'SeqNum' have been SACKed. Otherwise, the
// > routine returns false.
for (it = segment; it != m_sentList.end (); ++it)
for (it = segment; it != m_highestSack.first; ++it)
{
if (beginOfCurrentPacket >= m_highestSack.second)
{
NS_LOG_INFO ("seq=" << seq << " is not lost because there are no sacked segment ahead");
return false;
}
item = *it;
current = item->m_packet;
if (item->m_lost)
{
return true;
}
if (item->m_sacked)
{
NS_LOG_DEBUG ("Segment found to be SACKed, increasing counter and bytes by " <<
current->GetSize ());
NS_LOG_INFO ("Segment [" << beginOfCurrentPacket << ", " <<
beginOfCurrentPacket+item->m_packet->GetSize () <<
"] found to be SACKed");
++count;
bytes += current->GetSize ();
if ((count >= dupThresh) || (bytes > (dupThresh-1) * segmentSize))
{
NS_LOG_INFO ("seq=" << seq << " is lost because of 3 sacked blocks ahead");
return true;
}
}
@@ -724,12 +798,17 @@ TcpTxBuffer::IsLost (const SequenceNumber32 &seq, uint32_t dupThresh,
SequenceNumber32 beginOfCurrentPacket = m_firstByteSeq;
PacketList::const_iterator it;
if (seq >= m_highestSack.second)
{
return false;
}
// This O(n) method is called only once, and outside this class.
// It should not harm the performance
for (it = m_sentList.begin (); it != m_sentList.end (); ++it)
{
// Search for the right iterator before calling IsLost()
if (beginOfCurrentPacket > seq)
if (beginOfCurrentPacket >= seq)
{
return IsLost (beginOfCurrentPacket, it, dupThresh, segmentSize);
}
@@ -852,7 +931,7 @@ TcpTxBuffer::BytesInFlight (uint32_t dupThresh, uint32_t segmentSize) const
// (b) If S1 <= HighRxt: Pipe is incremented by 1 octet.
// (NOTE: we use the m_retrans flag instead of keeping and updating
// another variable). Only if the item is not marked as lost
else if (item->m_retrans && ! item->m_lost)
else if (item->m_retrans && !item->m_lost)
{
size += item->m_packet->GetSize ();
}
@@ -876,6 +955,8 @@ TcpTxBuffer::ResetScoreboard ()
(*it)->m_sacked = false;
beginOfCurrentPkt += (*it)->m_packet->GetSize ();
}
m_highestSack = std::make_pair (m_sentList.end (), SequenceNumber32 (0));
}
void
@@ -905,6 +986,8 @@ TcpTxBuffer::ResetSentList ()
{
m_sentSize = 0;
}
m_highestSack = std::make_pair (m_sentList.end (), SequenceNumber32 (0));
}
void
@@ -952,14 +1035,24 @@ Ptr<const TcpOptionSack>
TcpTxBuffer::CraftSackOption (const SequenceNumber32 &seq, uint8_t available) const
{
NS_LOG_FUNCTION (this);
PacketList::const_iterator it = m_sentList.begin ();
Ptr<TcpOptionSack> sackBlock = 0;
SequenceNumber32 beginOfCurrentPacket = m_firstByteSeq;
Ptr<Packet> current;
TcpTxItem *item;
NS_LOG_INFO ("Crafting a SACK block, available bytes: " << (uint32_t) available <<
" from seq: " << seq);
" from seq: " << seq << " buffer starts at seq " << m_firstByteSeq);
PacketList::const_iterator it;
if (m_highestSack.first == m_sentList.end ())
{
it = m_sentList.begin ();
}
else
{
it = m_highestSack.first;
beginOfCurrentPacket = m_highestSack.second;
}
while (it != m_sentList.end ())
{
@@ -1019,6 +1112,7 @@ TcpTxBuffer::CraftSackOption (const SequenceNumber32 &seq, uint8_t available) co
NS_LOG_DEBUG ("Filling the option: Adding [" << beginOfCurrentPacket <<
";" << endOfCurrentPacket << "], available space now : " <<
(uint32_t) (available - sackBlock->GetSerializedSize ()));
NS_ASSERT (beginOfCurrentPacket > m_firstByteSeq);
}
return sackBlock;

12
src/internet/model/tcp-tx-buffer.h
View File

@@ -409,7 +409,8 @@ private:
* \return the item that contains the right packet
*/
TcpTxItem* GetPacketFromList (PacketList &list, const SequenceNumber32 &startingSeq,
uint32_t numBytes, const SequenceNumber32 &requestedSeq) const;
uint32_t numBytes, const SequenceNumber32 &requestedSeq,
bool *listEdited) const;
/**
* \brief Merge two TcpTxItem
@@ -434,6 +435,13 @@ private:
*/
void SplitItems (TcpTxItem &t1, TcpTxItem &t2, uint32_t size) const;
/**
* \brief Find the highest SACK byte
* \return a pair with the highest byte and an iterator inside m_sentList
*/
std::pair <TcpTxBuffer::PacketList::const_iterator, SequenceNumber32>
GetHighestSacked () const;
PacketList m_appList; //!< Buffer for application data
PacketList m_sentList; //!< Buffer for sent (but not acked) data
uint32_t m_maxBuffer; //!< Max number of data bytes in buffer (SND.WND)
@@ -442,6 +450,8 @@ private:
TracedValue<SequenceNumber32> m_firstByteSeq; //!< Sequence number of the first byte in data (SND.UNA)
std::pair <PacketList::const_iterator, SequenceNumber32> m_highestSack; //!< Highest SACK byte
};
std::ostream & operator<< (std::ostream & os, TcpTxBuffer const & tcpTxBuf);