queue.cc

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/* -*-  Mode:C++; c-basic-offset:8; tab-width:8; indent-tabs-mode:t -*- */
/*
 * Copyright (c) 1996-1997 The Regents of the University of California.
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 *  This product includes software developed by the Network Research
 *  Group at Lawrence Berkeley National Laboratory.
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#ifndef lint
static const char rcsid[] =
    "@(#) $Header: /nfs/jade/vint/CVSROOT/ns-2/queue/queue.cc,v 1.29 2004/10/28 01:22:48 sfloyd Exp $ (LBL)";
#endif

#include "queue.h"
#include <math.h>
#include <stdio.h>

void PacketQueue::remove(Packet* target)
{
    for (Packet *pp= 0, *p= head_; p; pp= p, p= p->next_) {
        if (p == target) {
            if (!pp) deque();
            else {
                if (p == tail_) 
                    tail_= pp;
                pp->next_= p->next_;
                --len_;
                bytes_ -= hdr_cmn::access(p)->size();
            }
            return;
        }
    }
    fprintf(stderr, "PacketQueue:: remove() couldn't find target\n");
    abort();
}

/*
 * Remove packet pkt located after packet prev on the queue.  Either p or prev
 * could be NULL.  If prev is NULL then pkt must be the head of the queue.
 */
void PacketQueue::remove(Packet* pkt, Packet *prev) //XXX: screwy
{
    if (pkt) {
        if (head_ == pkt)
            PacketQueue::deque(); /* decrements len_ internally */
        else {
            prev->next_ = pkt->next_;
            if (tail_ == pkt)
                tail_ = prev;
            --len_;
            bytes_ -= hdr_cmn::access(pkt)->size();
        }
    }
    return;
}

void QueueHandler::handle(Event*)
{
    queue_.resume();
}

Queue::~Queue() {
}

Queue::Queue() : Connector(), blocked_(0), unblock_on_resume_(1), qh_(*this),
         pq_(0), 
         last_change_(0), /* temporarily NULL */
         old_util_(0), period_begin_(0), cur_util_(0), buf_slot_(0),
         util_buf_(NULL)
{
    bind("limit_", &qlim_);
    bind("util_weight_", &util_weight_);
    bind_bool("blocked_", &blocked_);
    bind_bool("unblock_on_resume_", &unblock_on_resume_);
    bind("util_check_intv_", &util_check_intv_);
    bind("util_records_", &util_records_);

    if (util_records_ > 0) {
        util_buf_ = new double[util_records_];
        if (util_buf_ == NULL) {
            printf("Error allocating util_bufs!");
            util_records_ = 0;
        }
        for (int i = 0; i < util_records_; i++) {
            util_buf_[i] = 0;
        }
    }
}

void Queue::recv(Packet* p, Handler*)
{
    double now = Scheduler::instance().clock();
    enque(p);
    if (!blocked_) {
        /*
         * We're not blocked.  Get a packet and send it on.
         * We perform an extra check because the queue
         * might drop the packet even if it was
         * previously empty!  (e.g., RED can do this.)
         */
        p = deque();
        if (p != 0) {
            utilUpdate(last_change_, now, blocked_);
            last_change_ = now;
            blocked_ = 1;
            target_->recv(p, &qh_);
        }
    }
}

void Queue::utilUpdate(double int_begin, double int_end, int link_state) {
double decay;

    decay = exp(-util_weight_ * (int_end - int_begin));
    old_util_ = link_state + (old_util_ - link_state) * decay;

    // PS: measuring peak utilization
    if (util_records_ == 0)
        return; // We don't track peak utilization

    double intv = int_end - int_begin;
    double tot_intv = int_begin - period_begin_;
    if (intv || tot_intv) {
        int guard = 0; // for protecting against long while loops 
        cur_util_ = (link_state * intv + cur_util_ * tot_intv) /
            (intv + tot_intv);
        while (tot_intv + intv > util_check_intv_ &&
               guard++ < util_records_) {

            period_begin_ = int_end;
            util_buf_[buf_slot_] = cur_util_;
            buf_slot_ = (buf_slot_ + 1) % util_records_;
            cur_util_ = link_state;
            intv -= util_check_intv_;
        }
    }
}

double Queue::utilization(void) 
{
    double now = Scheduler::instance().clock();
    
    utilUpdate(last_change_, now, blocked_);
    last_change_ = now;

    return old_util_;
            
}

double Queue::peak_utilization(void)
{
    double now = Scheduler::instance().clock();
    double peak = 0;
    int i;
    
    // PS: if peak_utilization tracking is disabled,
    // return the weighed avg instead
    if (util_records_ == 0)
        return utilization();

    utilUpdate(last_change_, now, blocked_);
    last_change_ = now;

    for (i = 0; i < util_records_; i++) {
        if (util_buf_[i] > peak)
            peak = util_buf_[i];
    }
    return peak;
}

void Queue::updateStats(int queuesize)
{
        double now = Scheduler::instance().clock();
        double newtime = now - total_time_;
        if (newtime > 0.0) {
                double oldave = true_ave_;
                double oldtime = total_time_;
                double newtime = now - total_time_;
                true_ave_ = (oldtime * oldave + newtime * queuesize) /now;
                total_time_ = now;
        }
}

void Queue::resume()
{
    double now = Scheduler::instance().clock();
    Packet* p = deque();
    if (p != 0) {
        target_->recv(p, &qh_);
    } else {
        if (unblock_on_resume_) {
            utilUpdate(last_change_, now, blocked_);
            last_change_ = now;
            blocked_ = 0;
        }
        else {
            utilUpdate(last_change_, now, blocked_);
            last_change_ = now;
            blocked_ = 1;
        }
    }
}

void Queue::reset()
{
    Packet* p;
    total_time_ = 0.0;
    true_ave_ = 0.0;
    while ((p = deque()) != 0)
        drop(p);
}

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