439 lines
16 KiB
C#
439 lines
16 KiB
C#
/*
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* Copyright (c) Contributors, http://opensimulator.org/
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* See CONTRIBUTORS.TXT for a full list of copyright holders.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of the OpenSimulator Project nor the
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* names of its contributors may be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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using System;
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using System.Collections;
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using System.Collections.Generic;
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using System.Reflection;
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using OpenSim.Framework;
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using log4net;
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namespace OpenSim.Region.ClientStack.LindenUDP
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{
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/// <summary>
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/// A hierarchical token bucket for bandwidth throttling. See
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/// http://en.wikipedia.org/wiki/Token_bucket for more information
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/// </summary>
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public class TokenBucket
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{
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private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
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public string Identifier { get; private set; }
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public int DebugLevel { get; set; }
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/// <summary>
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/// Number of ticks (ms) per quantum, drip rate and max burst
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/// are defined over this interval.
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/// </summary>
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protected const Int32 m_ticksPerQuantum = 1000;
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/// <summary>
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/// This is the number of quantums worth of packets that can
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/// be accommodated during a burst
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/// </summary>
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protected const Double m_quantumsPerBurst = 1.5;
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/// <summary>
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/// </summary>
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protected const Int32 m_minimumDripRate = 1400;
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/// <summary>Time of the last drip, in system ticks</summary>
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protected Int32 m_lastDrip;
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/// <summary>
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/// The number of bytes that can be sent at this moment. This is the
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/// current number of tokens in the bucket
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/// </summary>
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protected Int64 m_tokenCount;
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/// <summary>
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/// Map of children buckets and their requested maximum burst rate
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/// </summary>
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protected Dictionary<TokenBucket,Int64> m_children = new Dictionary<TokenBucket,Int64>();
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/// <summary>
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/// The parent bucket of this bucket, or null if this bucket has no
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/// parent. The parent bucket will limit the aggregate bandwidth of all
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/// of its children buckets
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/// </summary>
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public TokenBucket Parent { get; protected set; }
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/// <summary>
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/// Maximum burst rate in bytes per second. This is the maximum number
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/// of tokens that can accumulate in the bucket at any one time. This
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/// also sets the total request for leaf nodes
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/// </summary>
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protected Int64 m_burstRate;
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public Int64 RequestedBurstRate
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{
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get { return m_burstRate; }
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set { m_burstRate = (value < 0 ? 0 : value); }
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}
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public Int64 BurstRate
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{
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get {
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double rate = RequestedBurstRate * BurstRateModifier();
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if (rate < m_minimumDripRate * m_quantumsPerBurst)
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rate = m_minimumDripRate * m_quantumsPerBurst;
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return (Int64) rate;
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}
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}
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/// <summary>
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/// The requested drip rate for this particular bucket.
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/// </summary>
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/// <remarks>
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/// 0 then TotalDripRequest is used instead.
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/// Can never be above MaxDripRate.
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/// Tokens are added to the bucket at any time
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/// <seealso cref="RemoveTokens"/> is called, at the granularity of
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/// the system tick interval (typically around 15-22ms)
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/// FIXME: It is extremely confusing to be able to set a RequestedDripRate of 0 and then receive a positive
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/// number on get if TotalDripRequest is sent. This also stops us being able to retrieve the fact that
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/// RequestedDripRate is set to 0. Really, this should always return m_dripRate and then we can get
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/// (m_dripRate == 0 ? TotalDripRequest : m_dripRate) on some other properties.
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/// </remarks>
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public virtual Int64 RequestedDripRate
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{
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get { return (m_dripRate == 0 ? TotalDripRequest : m_dripRate); }
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set
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{
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if (value <= 0)
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m_dripRate = 0;
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else if (MaxDripRate > 0 && value > MaxDripRate)
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m_dripRate = MaxDripRate;
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else
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m_dripRate = value;
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m_burstRate = (Int64)((double)m_dripRate * m_quantumsPerBurst);
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if (Parent != null)
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Parent.RegisterRequest(this, m_dripRate);
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}
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}
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/// <summary>
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/// Gets the drip rate.
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/// </summary>
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/// <value>
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/// DripRate can never be above max drip rate or below min drip rate.
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/// If we are a child bucket then the drip rate return is modifed by the total load on the capacity of the
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/// parent bucket.
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/// </value>
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public virtual Int64 DripRate
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{
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get
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{
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double rate;
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// FIXME: This doesn't properly work if we have a parent and children and a requested drip rate set
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// on ourselves which is not equal to the child drip rates.
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if (Parent == null)
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{
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if (TotalDripRequest > 0)
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rate = Math.Min(RequestedDripRate, TotalDripRequest);
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else
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rate = RequestedDripRate;
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}
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else
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{
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rate = (double)RequestedDripRate * Parent.DripRateModifier();
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}
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if (rate < m_minimumDripRate)
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rate = m_minimumDripRate;
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else if (MaxDripRate > 0 && rate > MaxDripRate)
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rate = MaxDripRate;
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return (Int64)rate;
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}
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}
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protected Int64 m_dripRate;
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// <summary>
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// The maximum rate for flow control. Drip rate can never be greater than this.
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// </summary>
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public Int64 MaxDripRate { get; set; }
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/// <summary>
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/// The current total of the requested maximum burst rates of children buckets.
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/// </summary>
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public Int64 TotalDripRequest { get; protected set; }
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/// <summary>
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/// Default constructor
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/// </summary>
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/// <param name="identifier">Identifier for this token bucket</param>
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/// <param name="parent">Parent bucket if this is a child bucket, or
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/// null if this is a root bucket</param>
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/// <param name="requestedDripRate">
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/// Requested rate that the bucket fills, in bytes per
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/// second. If zero, the bucket always remains full.
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/// </param>
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public TokenBucket(string identifier, TokenBucket parent, Int64 requestedDripRate, Int64 maxDripRate)
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{
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Identifier = identifier;
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Parent = parent;
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RequestedDripRate = requestedDripRate;
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MaxDripRate = maxDripRate;
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m_lastDrip = Util.EnvironmentTickCount();
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}
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/// <summary>
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/// Compute a modifier for the MaxBurst rate. This is 1.0, meaning
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/// no modification if the requested bandwidth is less than the
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/// max burst bandwidth all the way to the root of the throttle
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/// hierarchy. However, if any of the parents is over-booked, then
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/// the modifier will be less than 1.
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/// </summary>
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protected double DripRateModifier()
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{
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Int64 driprate = DripRate;
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double modifier = driprate >= TotalDripRequest ? 1.0 : (double)driprate / (double)TotalDripRequest;
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// if (DebugLevel > 0)
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// m_log.DebugFormat(
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// "[TOKEN BUCKET]: Returning drip modifier {0}/{1} = {2} from {3}",
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// driprate, TotalDripRequest, modifier, Identifier);
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return modifier;
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}
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/// <summary>
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/// </summary>
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protected double BurstRateModifier()
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{
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// for now... burst rate is always m_quantumsPerBurst (constant)
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// larger than drip rate so the ratio of burst requests is the
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// same as the drip ratio
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return DripRateModifier();
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}
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/// <summary>
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/// Register drip rate requested by a child of this throttle. Pass the
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/// changes up the hierarchy.
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/// </summary>
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public void RegisterRequest(TokenBucket child, Int64 request)
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{
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lock (m_children)
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{
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m_children[child] = request;
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TotalDripRequest = 0;
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foreach (KeyValuePair<TokenBucket, Int64> cref in m_children)
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TotalDripRequest += cref.Value;
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}
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// Pass the new values up to the parent
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if (Parent != null)
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{
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Int64 effectiveDripRate;
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if (RequestedDripRate > 0)
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effectiveDripRate = Math.Min(RequestedDripRate, TotalDripRequest);
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else
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effectiveDripRate = TotalDripRequest;
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Parent.RegisterRequest(this, effectiveDripRate);
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}
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}
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/// <summary>
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/// Remove the rate requested by a child of this throttle. Pass the
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/// changes up the hierarchy.
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/// </summary>
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public void UnregisterRequest(TokenBucket child)
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{
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lock (m_children)
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{
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m_children.Remove(child);
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TotalDripRequest = 0;
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foreach (KeyValuePair<TokenBucket, Int64> cref in m_children)
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TotalDripRequest += cref.Value;
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}
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// Pass the new values up to the parent
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if (Parent != null)
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Parent.RegisterRequest(this,Math.Min(RequestedDripRate, TotalDripRequest));
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}
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/// <summary>
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/// Remove a given number of tokens from the bucket
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/// </summary>
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/// <param name="amount">Number of tokens to remove from the bucket</param>
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/// <returns>True if the requested number of tokens were removed from
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/// the bucket, otherwise false</returns>
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public bool RemoveTokens(Int64 amount)
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{
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// Deposit tokens for this interval
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Drip();
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// If we have enough tokens then remove them and return
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if (m_tokenCount - amount >= 0)
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{
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// we don't have to remove from the parent, the drip rate is already
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// reflective of the drip rate limits in the parent
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m_tokenCount -= amount;
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return true;
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}
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return false;
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}
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/// <summary>
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/// Deposit tokens into the bucket from a child bucket that did
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/// not use all of its available tokens
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/// </summary>
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protected void Deposit(Int64 count)
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{
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m_tokenCount += count;
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// Deposit the overflow in the parent bucket, this is how we share
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// unused bandwidth
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Int64 burstrate = BurstRate;
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if (m_tokenCount > burstrate)
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m_tokenCount = burstrate;
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}
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/// <summary>
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/// Add tokens to the bucket over time. The number of tokens added each
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/// call depends on the length of time that has passed since the last
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/// call to Drip
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/// </summary>
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/// <returns>True if tokens were added to the bucket, otherwise false</returns>
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protected void Drip()
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{
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// This should never happen... means we are a leaf node and were created
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// with no drip rate...
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if (DripRate == 0)
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{
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m_log.WarnFormat("[TOKENBUCKET] something odd is happening and drip rate is 0 for {0}", Identifier);
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return;
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}
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// Determine the interval over which we are adding tokens, never add
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// more than a single quantum of tokens
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Int32 deltaMS = Math.Min(Util.EnvironmentTickCountSubtract(m_lastDrip), m_ticksPerQuantum);
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m_lastDrip = Util.EnvironmentTickCount();
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// This can be 0 in the very unusual case that the timer wrapped
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// It can be 0 if we try add tokens at a sub-tick rate
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if (deltaMS <= 0)
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return;
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Deposit(deltaMS * DripRate / m_ticksPerQuantum);
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}
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}
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public class AdaptiveTokenBucket : TokenBucket
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{
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private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
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public bool AdaptiveEnabled { get; set; }
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/// <summary>
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/// Target drip rate for this bucket.
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/// </summary>
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/// <remarks>Usually set by the client. If adaptive is enabled then throttles will increase until we reach this.</remarks>
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public Int64 TargetDripRate
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{
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get { return m_targetDripRate; }
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set
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{
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m_targetDripRate = Math.Max(value, m_minimumFlow);
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}
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}
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protected Int64 m_targetDripRate;
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// <summary>
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// Adjust drip rate in response to network conditions.
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// </summary>
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public virtual Int64 AdjustedDripRate
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{
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get { return m_dripRate; }
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set
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{
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m_dripRate = OpenSim.Framework.Util.Clamp<Int64>(value, m_minimumFlow, TargetDripRate);
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m_burstRate = (Int64)((double)m_dripRate * m_quantumsPerBurst);
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if (Parent != null)
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Parent.RegisterRequest(this, m_dripRate);
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}
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}
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/// <summary>
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/// The minimum rate for flow control. Minimum drip rate is one
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/// packet per second. Open the throttle to 15 packets per second
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/// or about 160kbps.
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/// </summary>
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protected const Int64 m_minimumFlow = m_minimumDripRate * 15;
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public AdaptiveTokenBucket(string identifier, TokenBucket parent, Int64 requestedDripRate, Int64 maxDripRate, bool enabled)
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: base(identifier, parent, requestedDripRate, maxDripRate)
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{
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AdaptiveEnabled = enabled;
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if (AdaptiveEnabled)
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{
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// m_log.DebugFormat("[TOKENBUCKET]: Adaptive throttle enabled");
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TargetDripRate = m_minimumFlow;
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AdjustedDripRate = m_minimumFlow;
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}
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}
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// <summary>
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// Reliable packets sent to the client for which we never received an ack adjust the drip rate down.
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// </summary>
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public void ExpirePackets(Int32 count)
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{
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if (AdaptiveEnabled)
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{
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if (DebugLevel > 0)
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m_log.WarnFormat(
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"[ADAPTIVEBUCKET] drop {0} by {1} expired packets for {2}",
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AdjustedDripRate, count, Identifier);
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AdjustedDripRate = (Int64) (AdjustedDripRate / Math.Pow(2,count));
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}
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}
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// <summary>
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// Reliable packets acked by the client adjust the drip rate up.
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// </summary>
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public void AcknowledgePackets(Int32 count)
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{
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if (AdaptiveEnabled)
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AdjustedDripRate = AdjustedDripRate + count;
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}
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}
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} |