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more efficient way of checking for already seen packets: 

- uses Environment.TickCount for all timestamps (instead of more
  costly Util.UnixTimeSinceEpoch()
- takes care of Environment.TickCount overflow (which will happens
  after 24.8 days of system uptime)
- avoids instantiating List copies for each check
- gets rid of one lock() invocation
- moves calculation of loop invariant variable out of the loop itself
0.6.6-post-fixes
Dr Scofield 2009-06-25 07:59:25 +00:00
parent a1ba9dee8d
commit 77122d7861
1 changed files with 47 additions and 29 deletions
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66
OpenSim/Region/ClientStack/LindenUDP/LLPacketHandler.cs
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@ -90,10 +90,15 @@ namespace OpenSim.Region.ClientStack.LindenUDP
// the hashing. Expiration is less common and can be allowed the
// time for a linear scan.
//
private Dictionary<uint, int> m_DupeTracker =
new Dictionary<uint, int>();
private uint m_DupeTrackerWindow = 30;
private int m_DupeTrackerLastCheck = Environment.TickCount;
private List<uint> m_alreadySeenList = new List<uint>();
private Dictionary<uint, int>m_alreadySeenTracker = new Dictionary<uint, int>();
private int m_alreadySeenWindow = 30000;
private int m_lastAlreadySeenCheck = Environment.TickCount & Int32.MaxValue;
// private Dictionary<uint, int> m_DupeTracker =
// new Dictionary<uint, int>();
// private uint m_DupeTrackerWindow = 30;
// private int m_DupeTrackerLastCheck = Environment.TickCount;
// Values for the SimStatsReporter
//
@ -449,27 +454,40 @@ namespace OpenSim.Region.ClientStack.LindenUDP
// We can't keep an unlimited record of dupes. This will prune the
// dictionary by age.
//
private void PruneDupeTracker()
// NOTE: this needs to be called from within lock
// (m_alreadySeenTracker) context!
private void ExpireSeenPackets()
{
lock (m_DupeTracker)
{
if (m_DupeTracker.Count < 1024)
if (m_alreadySeenList.Count < 1024)
return;
if (Environment.TickCount - m_DupeTrackerLastCheck < 2000)
return;
int ticks = 0;
int tc = Environment.TickCount & Int32.MaxValue;
if (tc >= m_lastAlreadySeenCheck)
ticks = tc - m_lastAlreadySeenCheck;
else
ticks = Int32.MaxValue - m_lastAlreadySeenCheck + tc;
m_DupeTrackerLastCheck = Environment.TickCount;
if (ticks < 2000) return;
m_lastAlreadySeenCheck = tc;
Dictionary<uint, int> packs =
new Dictionary<uint, int>(m_DupeTracker);
foreach (uint pack in packs.Keys)
// we calculate the drop dead tick count here instead of
// in the loop: any packet with a timestamp before
// dropDeadTC can be expired
int dropDeadTC = tc - m_alreadySeenWindow;
int i = 0;
while (i < m_alreadySeenList.Count && m_alreadySeenTracker[m_alreadySeenList[i]] < dropDeadTC)
{
if (Util.UnixTimeSinceEpoch() - m_DupeTracker[pack] >
m_DupeTrackerWindow)
m_DupeTracker.Remove(pack);
m_alreadySeenTracker.Remove(m_alreadySeenList[i]);
i++;
}
// if we dropped packet from m_alreadySeenTracker we need
// to drop them from m_alreadySeenList as well, let's do
// that in one go: the list is ordered after all.
if (i > 0)
{
m_alreadySeenList.RemoveRange(0, i);
// m_log.DebugFormat("[CLIENT]: expired {0} packets, {1}:{2} left", i, m_alreadySeenList.Count, m_alreadySeenTracker.Count);
}
}
@ -545,18 +563,18 @@ namespace OpenSim.Region.ClientStack.LindenUDP
if (packet.Type != PacketType.AgentUpdate)
m_PacketsReceived++;
PruneDupeTracker();
// Check for duplicate packets.. packets that the client is
// resending because it didn't receive our ack
//
lock (m_DupeTracker)
lock (m_alreadySeenTracker)
{
if (m_DupeTracker.ContainsKey(packet.Header.Sequence))
ExpireSeenPackets();
if (m_alreadySeenTracker.ContainsKey(packet.Header.Sequence))
return;
m_DupeTracker.Add(packet.Header.Sequence,
Util.UnixTimeSinceEpoch());
m_alreadySeenTracker.Add(packet.Header.Sequence, Environment.TickCount & Int32.MaxValue);
m_alreadySeenList.Add(packet.Header.Sequence);
}
m_Client.ProcessInPacket(packet);