117 lines
3.9 KiB
C++
117 lines
3.9 KiB
C++
/*
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* Copyright (c) 2016 Universita' degli Studi di Napoli Federico II
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation;
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* Authors: Pasquale Imputato <p.imputato@gmail.com>
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* Stefano Avallone <stefano.avallone@unina.it>
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*
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* This code is a port of the dynamic queue limits library implemented
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* in the Linux kernel by
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* Author: Tom Herbert <therbert@google.com>
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*/
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#ifndef DYNAMIC_QUEUE_LIMITS_H
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#define DYNAMIC_QUEUE_LIMITS_H
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#include "queue-limits.h"
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#include "ns3/nstime.h"
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#include "ns3/traced-value.h"
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#include <limits.h>
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namespace ns3
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{
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/**
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* \ingroup network
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*
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* DynamicQueueLimits would be used in conjunction with a producer/consumer
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* type queue (possibly a netdevice queue).
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* Such a queue would have these general properties:
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*
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* 1) Objects are queued up to some limit specified as number of objects.
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* 2) Periodically a completion process executes which retires consumed
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* objects.
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* 3) Starvation occurs when limit has been reached, all queued data has
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* actually been consumed, but completion processing has not yet run
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* so queuing new data is blocked.
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* 4) Minimizing the amount of queued data is desirable.
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*
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* The goal of DynamicQueueLimits is to calculate the limit as the minimum
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* number of objects needed to prevent starvation.
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*
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* The primary functions of DynamicQueueLimits are:
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* Completed - called at completion time to indicate how many objects
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* were retired from the queue
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* Available - returns how many objects are available to be queued based
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* on the object limit and how many objects are already enqueued
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* Queued - called when objects are enqueued to record number of objects
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*
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*/
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class DynamicQueueLimits : public QueueLimits
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{
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public:
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/**
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* \brief Get the type ID.
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* \return the object TypeId
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*/
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static TypeId GetTypeId();
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DynamicQueueLimits();
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~DynamicQueueLimits() override;
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void Reset() override;
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void Completed(uint32_t count) override;
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int32_t Available() const override;
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void Queued(uint32_t count) override;
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private:
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/**
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* Calculates the difference between the two operators and
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* returns the number if positive, zero otherwise.
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* \param a First operator.
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* \param b Second operator.
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* \returns the difference between a and b if positive, zero otherwise.
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*/
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int32_t Posdiff(int32_t a, int32_t b);
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// Fields accessed in enqueue path
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uint32_t m_numQueued{0}; //!< Total ever queued
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uint32_t m_adjLimit{0}; //!< limit + num_completed
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uint32_t m_lastObjCnt{0}; //!< Count at last queuing
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// Fields accessed only by completion path
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TracedValue<uint32_t> m_limit; //!< Current limit
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uint32_t m_numCompleted{0}; //!< Total ever completed
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uint32_t m_prevOvlimit{0}; //!< Previous over limit
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uint32_t m_prevNumQueued{0}; //!< Previous queue total
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uint32_t m_prevLastObjCnt{0}; //!< Previous queuing cnt
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uint32_t m_lowestSlack{std::numeric_limits<uint32_t>::max()}; //!< Lowest slack found
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Time m_slackStartTime{Seconds(0)}; //!< Time slacks seen
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// Configuration
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uint32_t m_maxLimit; //!< Max limit
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uint32_t m_minLimit; //!< Minimum limit
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Time m_slackHoldTime; //!< Time to measure slack
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};
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} // namespace ns3
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#endif /* DYNAMIC_QUEUE_LIMITS_H */
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