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wifi: Cache the result of ChannelAccessManager::GetAccessGrantStart()

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Also, cleanup its implementation
This commit is contained in:
Stefano Avallone
2024-04-12 13:09:08 +02:00
parent 6a2b47cf95
commit 12d8a340bf
2 changed files with 74 additions and 47 deletions
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93
src/wifi/model/channel-access-manager.cc
View File

@@ -513,13 +513,14 @@ ChannelAccessManager::DoGrantDcfAccess()
{
NS_LOG_FUNCTION(this);
uint32_t k = 0;
Time now = Simulator::Now();
const auto now = Simulator::Now();
const auto accessGrantStart = GetAccessGrantStart();
for (auto i = m_txops.begin(); i != m_txops.end(); k++)
{
Ptr<Txop> txop = *i;
if (txop->GetAccessStatus(m_linkId) == Txop::REQUESTED &&
(!txop->IsQosTxop() || !StaticCast<QosTxop>(txop)->EdcaDisabled(m_linkId)) &&
GetBackoffEndFor(txop) <= now)
GetBackoffEndFor(txop, accessGrantStart) <= now)
{
/**
* This is the first Txop we find with an expired backoff and which
@@ -534,7 +535,7 @@ ChannelAccessManager::DoGrantDcfAccess()
{
Ptr<Txop> otherTxop = *j;
if (otherTxop->GetAccessStatus(m_linkId) == Txop::REQUESTED &&
GetBackoffEndFor(otherTxop) <= now)
GetBackoffEndFor(otherTxop, accessGrantStart) <= now)
{
NS_LOG_DEBUG(
"dcf " << k << " needs access. backoff expired. internal collision. slots="
@@ -602,58 +603,47 @@ ChannelAccessManager::AccessTimeout()
Time
ChannelAccessManager::GetAccessGrantStart(bool ignoreNav) const
{
NS_LOG_FUNCTION(this);
const Time& sifs = GetSifs();
Time rxAccessStart = m_lastRx.end + sifs;
NS_LOG_FUNCTION(this << ignoreNav);
auto rxAccessStart = m_lastRx.end;
if ((m_lastRx.end <= Simulator::Now()) && !m_lastRxReceivedOk)
{
rxAccessStart += GetEifsNoDifs();
}
// an EDCA TXOP is obtained based solely on activity of the primary channel
// (Sec. 10.23.2.5 of IEEE 802.11-2020)
Time busyAccessStart = m_lastBusyEnd.at(WIFI_CHANLIST_PRIMARY) + sifs;
Time txAccessStart = m_lastTxEnd + sifs;
Time navAccessStart = m_lastNavEnd + sifs;
Time ackTimeoutAccessStart = m_lastAckTimeoutEnd + sifs;
Time ctsTimeoutAccessStart = m_lastCtsTimeoutEnd + sifs;
Time switchingAccessStart = m_lastSwitchingEnd + sifs;
Time accessGrantedStart;
if (ignoreNav)
{
accessGrantedStart = std::max({rxAccessStart,
busyAccessStart,
txAccessStart,
ackTimeoutAccessStart,
ctsTimeoutAccessStart,
switchingAccessStart});
}
else
{
accessGrantedStart = std::max({rxAccessStart,
busyAccessStart,
txAccessStart,
navAccessStart,
ackTimeoutAccessStart,
ctsTimeoutAccessStart,
switchingAccessStart});
}
NS_LOG_INFO("access grant start=" << accessGrantedStart.As(Time::US)
<< ", rx access start=" << rxAccessStart.As(Time::US)
<< ", busy access start=" << busyAccessStart.As(Time::US)
<< ", tx access start=" << txAccessStart.As(Time::US)
<< ", nav access start=" << navAccessStart.As(Time::US)
<< ", switching access start="
<< switchingAccessStart.As(Time::US));
return accessGrantedStart;
const auto busyAccessStart = m_lastBusyEnd.at(WIFI_CHANLIST_PRIMARY);
const auto navAccessStart = ignoreNav ? Time{0} : m_lastNavEnd;
const auto accessGrantedStart = std::max({rxAccessStart,
busyAccessStart,
m_lastTxEnd,
navAccessStart,
m_lastAckTimeoutEnd,
m_lastCtsTimeoutEnd,
m_lastSwitchingEnd});
NS_LOG_INFO("access grant start="
<< accessGrantedStart.As(Time::US)
<< ", rx access start=" << rxAccessStart.As(Time::US) << ", busy access start="
<< busyAccessStart.As(Time::US) << ", tx access start=" << m_lastTxEnd.As(Time::US)
<< ", nav access start=" << navAccessStart.As(Time::US)
<< ", switching access start=" << m_lastSwitchingEnd.As(Time::US));
return accessGrantedStart + GetSifs();
}
Time
ChannelAccessManager::GetBackoffStartFor(Ptr<Txop> txop)
{
NS_LOG_FUNCTION(this << txop);
Time mostRecentEvent =
return GetBackoffStartFor(txop, GetAccessGrantStart());
}
Time
ChannelAccessManager::GetBackoffStartFor(Ptr<Txop> txop, Time accessGrantStart) const
{
NS_LOG_FUNCTION(this << txop << accessGrantStart.As(Time::S));
const auto mostRecentEvent =
std::max({txop->GetBackoffStart(m_linkId),
GetAccessGrantStart() + (txop->GetAifsn(m_linkId) * GetSlot())});
accessGrantStart + (txop->GetAifsn(m_linkId) * GetSlot())});
NS_LOG_DEBUG("Backoff start for " << txop->GetWifiMacQueue()->GetAc() << ": "
<< mostRecentEvent.As(Time::US));
@@ -662,9 +652,16 @@ ChannelAccessManager::GetBackoffStartFor(Ptr<Txop> txop)
Time
ChannelAccessManager::GetBackoffEndFor(Ptr<Txop> txop)
{
return GetBackoffEndFor(txop, GetAccessGrantStart());
}
Time
ChannelAccessManager::GetBackoffEndFor(Ptr<Txop> txop, Time accessGrantStart) const
{
NS_LOG_FUNCTION(this << txop);
Time backoffEnd = GetBackoffStartFor(txop) + (txop->GetBackoffSlots(m_linkId) * GetSlot());
Time backoffEnd =
GetBackoffStartFor(txop, accessGrantStart) + (txop->GetBackoffSlots(m_linkId) * GetSlot());
NS_LOG_DEBUG("Backoff end for " << txop->GetWifiMacQueue()->GetAc() << ": "
<< backoffEnd.As(Time::US));
@@ -676,9 +673,10 @@ ChannelAccessManager::UpdateBackoff()
{
NS_LOG_FUNCTION(this);
uint32_t k = 0;
const auto accessGrantStart = GetAccessGrantStart();
for (auto txop : m_txops)
{
Time backoffStart = GetBackoffStartFor(txop);
Time backoffStart = GetBackoffStartFor(txop, accessGrantStart);
if (backoffStart <= Simulator::Now())
{
uint32_t nIntSlots = ((Simulator::Now() - backoffStart) / GetSlot()).GetHigh();
@@ -715,12 +713,13 @@ ChannelAccessManager::DoRestartAccessTimeoutIfNeeded()
* if there is one, how many slots for AIFS+backoff does it require ?
*/
bool accessTimeoutNeeded = false;
Time expectedBackoffEnd = Simulator::GetMaximumSimulationTime();
auto expectedBackoffEnd = Simulator::GetMaximumSimulationTime();
const auto accessGrantStart = GetAccessGrantStart();
for (auto txop : m_txops)
{
if (txop->GetAccessStatus(m_linkId) == Txop::REQUESTED)
{
Time tmp = GetBackoffEndFor(txop);
Time tmp = GetBackoffEndFor(txop, accessGrantStart);
if (tmp > Simulator::Now())
{
accessTimeoutNeeded = true;

28
src/wifi/model/channel-access-manager.h
View File

@@ -359,15 +359,40 @@ class ChannelAccessManager : public Object
* \return the current registered listener for PHY events on the given PHY
*/
std::shared_ptr<PhyListener> GetPhyListener(Ptr<WifiPhy> phy) const;
/**
* Initialize the structures holding busy end times per channel type (primary,
* secondary, etc.) and per 20 MHz channel.
*/
void InitLastBusyStructs();
/**
* Update backoff slots for all Txops.
*/
void UpdateBackoff();
/**
* This overload is provided to enable caching the value returned by GetAccessGrantStart(),
* which is independent of the given Txop object.
*
* \param txop the Txop
* \param accessGrantStart the value returned by GetAccessGrantStart()
*
* \return the time when the backoff procedure started
*/
Time GetBackoffStartFor(Ptr<Txop> txop, Time accessGrantStart) const;
/**
* This overload is provided to enable caching the value returned by GetAccessGrantStart(),
* which is independent of the given Txop object.
*
* \param txop the Txop
* \param accessGrantStart the value returned by GetAccessGrantStart()
*
* \return the time when the backoff procedure ended (or will ended)
*/
Time GetBackoffEndFor(Ptr<Txop> txop, Time accessGrantStart) const;
/**
* Return the time when the backoff procedure
* started for the given Txop.
@@ -404,6 +429,7 @@ class ChannelAccessManager : public Object
* (e.g. backoff procedure expired).
*/
void AccessTimeout();
/**
* Grant access to Txop using DCF/EDCF contention rules
*/
@@ -415,12 +441,14 @@ class ChannelAccessManager : public Object
* \return the SIFS duration
*/
virtual Time GetSifs() const;
/**
* Return the slot duration for this PHY.
*
* \return the slot duration
*/
virtual Time GetSlot() const;
/**
* Return the EIFS duration minus a DIFS.
*