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unison/src/internet/model/codel-queue.cc

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/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
* Copyright (c) 2012 Andrew McGregor
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation;
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* Codel, the COntrolled DELay Queueing discipline
* Based on ns2 simulation code presented by Kathie Nichols
*
* This port based on linux kernel code by
* Authors: Dave Täht <d@taht.net>
* Eric Dumazet <edumazet@google.com>
*
* Ported to ns-3 by: Andrew McGregor <andrewmcgr@gmail.com>
*/
#include "ns3/log.h"
#include "ns3/enum.h"
#include "ns3/uinteger.h"
#include "ns3/abort.h"
#include "codel-queue.h"
NS_LOG_COMPONENT_DEFINE ("CoDelQueue");
namespace ns3 {
/* borrowed from the linux kernel */
static inline uint32_t ReciprocalDivide (uint32_t A, uint32_t R)
{
return (uint32_t)(((uint64_t)A * R) >> 32);
}
/* end kernel borrowings */
static uint32_t CoDelGetTime (void)
{
Time time = Simulator::Now ();
uint64_t ns = time.GetNanoSeconds ();
return ns >> CODEL_SHIFT;
}
class CoDelTimestampTag : public Tag
{
public:
CoDelTimestampTag ();
static TypeId GetTypeId (void);
virtual TypeId GetInstanceTypeId (void) const;
virtual uint32_t GetSerializedSize (void) const;
virtual void Serialize (TagBuffer i) const;
virtual void Deserialize (TagBuffer i);
virtual void Print (std::ostream &os) const;
Time GetTxTime (void) const;
private:
uint64_t m_creationTime;
};
CoDelTimestampTag::CoDelTimestampTag ()
: m_creationTime (Simulator::Now ().GetTimeStep ())
{
}
TypeId
CoDelTimestampTag::GetTypeId (void)
{
static TypeId tid = TypeId ("ns3::CoDelTimestampTag")
.SetParent<Tag> ()
.AddConstructor<CoDelTimestampTag> ()
.AddAttribute ("CreationTime",
"The time at which the timestamp was created",
StringValue ("0.0s"),
MakeTimeAccessor (&CoDelTimestampTag::GetTxTime),
MakeTimeChecker ())
;
return tid;
}
TypeId
CoDelTimestampTag::GetInstanceTypeId (void) const
{
return GetTypeId ();
}
uint32_t
CoDelTimestampTag::GetSerializedSize (void) const
{
return 8;
}
void
CoDelTimestampTag::Serialize (TagBuffer i) const
{
i.WriteU64 (m_creationTime);
}
void
CoDelTimestampTag::Deserialize (TagBuffer i)
{
m_creationTime = i.ReadU64 ();
}
void
CoDelTimestampTag::Print (std::ostream &os) const
{
os << "CreationTime=" << m_creationTime;
}
Time
CoDelTimestampTag::GetTxTime (void) const
{
return TimeStep (m_creationTime);
}
NS_OBJECT_ENSURE_REGISTERED (CoDelQueue);
TypeId CoDelQueue::GetTypeId (void)
{
static TypeId tid = TypeId ("ns3::CoDelQueue")
.SetParent<Queue> ()
.AddConstructor<CoDelQueue> ()
.AddAttribute ("Mode",
"Whether to use Bytes (see MaxBytes) or Packets (see MaxPackets) as the maximum queue size metric.",
EnumValue (QUEUE_MODE_BYTES),
MakeEnumAccessor (&CoDelQueue::SetMode),
MakeEnumChecker (QUEUE_MODE_BYTES, "QUEUE_MODE_BYTES",
QUEUE_MODE_PACKETS, "QUEUE_MODE_PACKETS"))
.AddAttribute ("MaxPackets",
"The maximum number of packets accepted by this CoDelQueue.",
UintegerValue (DEFAULT_CODEL_LIMIT),
MakeUintegerAccessor (&CoDelQueue::m_maxPackets),
MakeUintegerChecker<uint32_t> ())
.AddAttribute ("MaxBytes",
"The maximum number of bytes accepted by this CoDelQueue.",
UintegerValue (1500 * DEFAULT_CODEL_LIMIT),
MakeUintegerAccessor (&CoDelQueue::m_maxBytes),
MakeUintegerChecker<uint32_t> ())
.AddAttribute ("MinBytes",
"The CoDel algorithm minbytes parameter.",
UintegerValue (1500),
MakeUintegerAccessor (&CoDelQueue::m_minBytes),
MakeUintegerChecker<uint32_t> ())
.AddAttribute ("Interval",
"The CoDel algorithm interval",
StringValue ("100ms"),
MakeTimeAccessor (&CoDelQueue::m_interval),
MakeTimeChecker ())
.AddAttribute ("Target",
"The CoDel algorithm target queue delay",
StringValue ("5ms"),
MakeTimeAccessor (&CoDelQueue::m_target),
MakeTimeChecker ())
.AddTraceSource ("Count",
"CoDel count",
MakeTraceSourceAccessor (&CoDelQueue::m_count))
.AddTraceSource ("DropCount",
"CoDel drop count",
MakeTraceSourceAccessor (&CoDelQueue::m_dropCount))
.AddTraceSource ("LastCount",
"CoDel lastcount",
MakeTraceSourceAccessor (&CoDelQueue::m_lastCount))
.AddTraceSource ("DropState",
"Dropping state",
MakeTraceSourceAccessor (&CoDelQueue::m_dropping))
.AddTraceSource ("BytesInQueue",
"Number of bytes in the queue",
MakeTraceSourceAccessor (&CoDelQueue::m_bytesInQueue))
.AddTraceSource ("Sojourn",
"Time in the queue",
MakeTraceSourceAccessor (&CoDelQueue::m_sojourn))
.AddTraceSource ("DropNext",
"Time until next packet drop",
MakeTraceSourceAccessor (&CoDelQueue::m_dropNext))
;
return tid;
}
CoDelQueue::CoDelQueue ()
: Queue (),
m_packets (),
m_maxBytes (),
m_bytesInQueue (0),
m_count (0),
m_dropCount (0),
m_lastCount (0),
m_dropping (false),
m_recInvSqrt (~0U >> REC_INV_SQRT_SHIFT),
m_firstAboveTime (0),
m_dropNext (0),
m_state1 (0),
m_state2 (0),
m_state3 (0),
m_states (0),
m_dropOverLimit (0),
m_sojourn (0)
{
NS_LOG_FUNCTION (this);
}
CoDelQueue::~CoDelQueue ()
{
NS_LOG_FUNCTION (this);
}
void
CoDelQueue::NewtonStep (void)
{
NS_LOG_FUNCTION (this);
uint32_t invsqrt = ((uint32_t) m_recInvSqrt) << REC_INV_SQRT_SHIFT;
uint32_t invsqrt2 = ((uint64_t) invsqrt * invsqrt) >> 32;
uint64_t val = (3ll << 32) - ((uint64_t) m_count * invsqrt2);
val >>= 2; /* avoid overflow */
val = (val * invsqrt) >> (32 - 2 + 1);
m_recInvSqrt = val >> REC_INV_SQRT_SHIFT;
}
uint32_t
CoDelQueue::ControlLaw (uint32_t t)
{
NS_LOG_FUNCTION (this);
return t + ReciprocalDivide (Time2CoDel (m_interval), m_recInvSqrt << REC_INV_SQRT_SHIFT);
}
void
CoDelQueue::SetMode (CoDelQueue::QueueMode mode)
{
NS_LOG_FUNCTION (mode);
m_mode = mode;
}
CoDelQueue::QueueMode
CoDelQueue::GetMode (void)
{
NS_LOG_FUNCTION (this);
return m_mode;
}
bool
CoDelQueue::DoEnqueue (Ptr<Packet> p)
{
NS_LOG_FUNCTION (this << p);
if (m_mode == QUEUE_MODE_PACKETS && (m_packets.size () + 1 > m_maxPackets))
{
NS_LOG_LOGIC ("Queue full (at max packets) -- droppping pkt");
Drop (p);
++m_dropOverLimit;
return false;
}
if (m_mode == QUEUE_MODE_BYTES && (m_bytesInQueue + p->GetSize () > m_maxBytes))
{
NS_LOG_LOGIC ("Queue full (packet would exceed max bytes) -- droppping pkt");
Drop (p);
++m_dropOverLimit;
return false;
}
// Tag packet with current time for DoDequeue() to compute sojourn time
CoDelTimestampTag tag;
p->AddPacketTag (tag);
m_bytesInQueue += p->GetSize ();
m_packets.push (p);
NS_LOG_LOGIC ("Number packets " << m_packets.size ());
NS_LOG_LOGIC ("Number bytes " << m_bytesInQueue);
return true;
}
bool
CoDelQueue::OkToDrop (Ptr<Packet> p, uint32_t now)
{
NS_LOG_FUNCTION (this);
CoDelTimestampTag tag;
bool okToDrop;
p->FindFirstMatchingByteTag (tag);
bool found = p->RemovePacketTag (tag);
NS_ASSERT_MSG (found, "found a packet without an input timestamp tag");
NS_UNUSED (found); //silence compiler warning
Time delta = Simulator::Now () - tag.GetTxTime ();
NS_LOG_INFO ("Sojourn time " << delta.GetSeconds ());
m_sojourn = delta;
uint32_t sojournTime = Time2CoDel (delta);
if (CoDelTimeBefore (sojournTime, Time2CoDel (m_target))
|| m_bytesInQueue < m_minBytes)
{
// went below so we'll stay below for at least q->interval
NS_LOG_LOGIC ("Sojourn time is below target or number of bytes in queue is less than minBytes; packet should not be dropped");
m_firstAboveTime = 0;
return false;
}
okToDrop = false;
if (m_firstAboveTime == 0)
{
/* just went above from below. If we stay above
* for at least q->interval we'll say it's ok to drop
*/
NS_LOG_LOGIC ("Sojourn time has just gone above target from below, need to stay above for at least q->interval before packet can be dropped. ");
m_firstAboveTime = now + Time2CoDel (m_interval);
}
else
if (CoDelTimeAfter (now, m_firstAboveTime))
{
NS_LOG_LOGIC ("Sojourn time has been above target for at least q->interval; it's OK to (possibly) drop packet.");
okToDrop = true;
++m_state1;
}
return okToDrop;
}
Ptr<Packet>
CoDelQueue::DoDequeue (void)
{
NS_LOG_FUNCTION (this);
if (m_packets.empty ())
{
// Leave dropping state when queue is empty
m_dropping = false;
m_firstAboveTime = 0;
NS_LOG_LOGIC ("Queue empty");
return 0;
}
uint32_t now = CoDelGetTime ();
Ptr<Packet> p = m_packets.front ();
m_packets.pop ();
m_bytesInQueue -= p->GetSize ();
NS_LOG_LOGIC ("Popped " << p);
NS_LOG_LOGIC ("Number packets remaining " << m_packets.size ());
NS_LOG_LOGIC ("Number bytes remaining " << m_bytesInQueue);
// Determine if p should be dropped
bool okToDrop = OkToDrop (p, now);
if (m_dropping)
{ // In the dropping state (sojourn time has gone above target and hasn't come down yet)
// Check if we can leave the dropping state or next drop should occur
NS_LOG_LOGIC ("In dropping state, check if it's OK to leave or next drop should occur");
if (!okToDrop)
{
/* sojourn time fell below target - leave dropping state */
NS_LOG_LOGIC ("Sojourn time goes below target, it's OK to leave dropping state.");
m_dropping = false;
}
else
if (CoDelTimeAfterEq (now, m_dropNext))
{
m_state2++;
while (m_dropping && CoDelTimeAfterEq (now, m_dropNext))
{
// It's time for the next drop. Drop the current packet and
// dequeue the next. The dequeue might take us out of dropping
// state. If not, schedule the next drop.
// A large amount of packets in queue might result in drop
// rates so high that the next drop should happen now,
// hence the while loop.
NS_LOG_LOGIC ("Sojourn time is still above target and it's time for next drop; dropping " << p);
Drop (p);
++m_dropCount;
++m_count;
NewtonStep ();
if (m_packets.empty ())
{
m_dropping = false;
NS_LOG_LOGIC ("Queue empty");
++m_states;
return 0;
}
p = m_packets.front ();
m_packets.pop ();
m_bytesInQueue -= p->GetSize ();
NS_LOG_LOGIC ("Popped " << p);
NS_LOG_LOGIC ("Number packets remaining " << m_packets.size ());
NS_LOG_LOGIC ("Number bytes remaining " << m_bytesInQueue);
if (!OkToDrop (p, now))
{
/* leave dropping state */
NS_LOG_LOGIC ("Leaving dropping state");
m_dropping = false;
}
else
{
/* schedule the next drop */
NS_LOG_LOGIC ("Running ControlLaw for input m_dropNext: " << (double)m_dropNext / 1000000);
m_dropNext = ControlLaw (m_dropNext);
NS_LOG_LOGIC ("Scheduled next drop at " << (double)m_dropNext / 1000000);
}
}
}
}
else
{
// Not in the dropping state
// Decide if we have to enter the dropping state and drop the first packet
NS_LOG_LOGIC ("Not in dropping state; decide if we have to enter the state and drop the first packet");
if (okToDrop)
{
// Drop the first packet and enter dropping state unless the queue is empty
NS_LOG_LOGIC ("Sojourn time goes above target, dropping the first packet " << p << " and entering the dropping state");
++m_dropCount;
Drop (p);
if (m_packets.empty ())
{
m_dropping = false;
okToDrop = false;
NS_LOG_LOGIC ("Queue empty");
++m_states;
}
else
{
p = m_packets.front ();
m_packets.pop ();
m_bytesInQueue -= p->GetSize ();
NS_LOG_LOGIC ("Popped " << p);
NS_LOG_LOGIC ("Number packets remaining " << m_packets.size ());
NS_LOG_LOGIC ("Number bytes remaining " << m_bytesInQueue);
okToDrop = OkToDrop (p, now);
m_dropping = true;
}
++m_state3;
/*
* if min went above target close to when we last went below it
* assume that the drop rate that controlled the queue on the
* last cycle is a good starting point to control it now.
*/
int delta = m_count - m_lastCount;
if (delta > 1 && CoDelTimeBefore (now - m_dropNext, 16 * Time2CoDel (m_interval)))
{
m_count = delta;
NewtonStep ();
}
else
{
m_count = 1;
m_recInvSqrt = ~0U >> REC_INV_SQRT_SHIFT;
}
m_lastCount = m_count;
NS_LOG_LOGIC ("Running ControlLaw for input now: " << (double)now);
m_dropNext = ControlLaw (now);
NS_LOG_LOGIC ("Scheduled next drop at " << (double)m_dropNext / 1000000 << " now " << (double)now / 1000000);
}
}
++m_states;
return p;
}
uint32_t
CoDelQueue::GetQueueSize (void)
{
NS_LOG_FUNCTION (this);
if (GetMode () == QUEUE_MODE_BYTES)
{
return m_bytesInQueue;
}
else if (GetMode () == QUEUE_MODE_PACKETS)
{
return m_packets.size ();
}
else
{
NS_ABORT_MSG ("Unknown mode.");
}
}
uint32_t
CoDelQueue::GetDropOverLimit (void)
{
return m_dropOverLimit;
}
uint32_t
CoDelQueue::GetDropCount (void)
{
return m_dropCount;
}
Time
CoDelQueue::GetTarget (void)
{
return m_target;
}
Time
CoDelQueue::GetInterval (void)
{
return m_interval;
}
uint32_t
CoDelQueue::GetDropNext (void)
{
return m_dropNext;
}
Ptr<const Packet>
CoDelQueue::DoPeek (void) const
{
NS_LOG_FUNCTION (this);
if (m_packets.empty ())
{
NS_LOG_LOGIC ("Queue empty");
return 0;
}
Ptr<Packet> p = m_packets.front ();
NS_LOG_LOGIC ("Number packets " << m_packets.size ());
NS_LOG_LOGIC ("Number bytes " << m_bytesInQueue);
return p;
}
bool
CoDelQueue::CoDelTimeAfter (uint32_t a, uint32_t b)
{
return ((int)(a) - (int)(b) > 0);
}
bool
CoDelQueue::CoDelTimeAfterEq (uint32_t a, uint32_t b)
{
return ((int)(a) - (int)(b) >= 0);
}
bool
CoDelQueue::CoDelTimeBefore (uint32_t a, uint32_t b)
{
return ((int)(a) - (int)(b) < 0);
}
bool
CoDelQueue::CoDelTimeBeforeEq (uint32_t a, uint32_t b)
{
return ((int)(a) - (int)(b) <= 0);
}
uint32_t
CoDelQueue::Time2CoDel (Time t)
{
return (t.GetNanoSeconds () >> CODEL_SHIFT);
}
} // namespace ns3
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