feat: Rework the buffer cleanup to happen post-handling of packets

include/core/monomux/adt/RingBuffer.hpp

@@ -44,44 +44,11 @@ class RingBufferBase
 
   const std::size_t OriginalCapacity;
 
-  struct SuccessfulBufferlessAccess
-  {
-    std::chrono::time_point<std::chrono::system_clock> Created;
-    std::chrono::time_point<std::chrono::system_clock> Last;
-
-    SuccessfulBufferlessAccess() : Created(std::chrono::system_clock::now())
-    {
-      stamp();
-    }
-
-    void stamp() noexcept { Last = std::chrono::system_clock::now(); }
-  };
-
 public:
   std::size_t capacity() const noexcept { return Capacity; }
   std::size_t size() const noexcept { return Size; }
   bool empty() const noexcept { return Size == 0; }
 
-  /// Clients to a \p RingBuffer might be able to do the associated operation
-  /// without making use of the buffer. The shrinking heuristic only calculates
-  /// if the buffer is accessed, which means that direct, buffer-not-using
-  /// operations will not trigger a potential \p shrink(), which keeps a grown
-  /// buffer's allocation alive even if there is no need for that much space.
-  ///
-  /// This method is used to signal the heuristic that the client was able to
-  /// do something without involving the buffer. Calling this method has no
-  /// effect on the actual contents of the buffer, if there is any.
-  void signalStatisticForSuccessfulUnbufferedAccess() noexcept
-  {
-    if (Size != 0)
-      return;
-    if (!SuccessfulBufferlessAccessCounter)
-      SuccessfulBufferlessAccessCounter.emplace();
-    else
-      SuccessfulBufferlessAccessCounter->stamp();
-    mayBeValley();
-  }
-
 protected:
   /// The physical size of the allocated buffer.
   std::size_t Capacity = 0;
@@ -91,6 +58,7 @@ class RingBufferBase
   RingBufferBase(std::size_t Capacity)
     : OriginalCapacity(Capacity), Capacity(Capacity)
   {
+    markAccess();
     SizePeaks.resize(((Capacity / Kilo) + 2) * 1);
   }
 
@@ -99,23 +67,27 @@ class RingBufferBase
   void incSize() noexcept
   {
     ++Size;
+    markAccess();
     mayBePeak();
   }
   void decSize() noexcept
   {
     assert(Size != 0);
     --Size;
+    markAccess();
     mayBeValley();
   }
   void addSize(std::size_t N) noexcept
   {
     Size += N;
+    markAccess();
     mayBePeak();
   }
   void subSize(std::size_t N) noexcept
   {
     assert(N <= Size);
     Size -= N;
+    markAccess();
     mayBeValley();
   }
   void zeroSize() noexcept
@@ -132,17 +104,17 @@ class RingBufferBase
     if (Capacity <= OriginalCapacity)
       return false;
 
-    // For each KiB of buffer space, we need at least this many successful
-    // small accesses before the shrinking of the buffer is considered.
-    static constexpr std::size_t TimeThreshold = 30;
-    if (SuccessfulBufferlessAccessCounter &&
-        SuccessfulBufferlessAccessCounter->Last -
-            SuccessfulBufferlessAccessCounter->Created >=
-          std::chrono::seconds(TimeThreshold))
+    static constexpr std::size_t TimeThresholdSeconds = 60;
+    if (std::chrono::system_clock::now() - LastAccess >=
+        std::chrono::seconds(TimeThresholdSeconds))
       // Consider the buffer for shrinking if operations were successful without
-      // it "too many" times.
+      // accessing the buffer for a sufficient amount of time.
       return true;
 
+    // Otherwise, if the buffer is continously used for a sufficient amount of
+    // time, consider shrinking it in case at least half of the recent peaks
+    // (inbetween each valley, i.e. zeroing the size) would've fit into the
+    // original buffer capacity too.
     std::size_t ZeroPeaks = 0;
     std::size_t SufficientlySmallPeaks = 0;
     for (std::size_t Peak : SizePeaks)
@@ -160,7 +132,6 @@ class RingBufferBase
     for (std::size_t& SPV : SizePeaks)
       SPV = 0;
     CurrentPeakIndex = 0;
-    SuccessfulBufferlessAccessCounter.reset();
     mayBePeak();
   }
 
@@ -170,15 +141,16 @@ class RingBufferBase
   std::vector<std::size_t> SizePeaks;
   std::size_t CurrentPeakIndex = 0;
 
-  std::optional<SuccessfulBufferlessAccess> SuccessfulBufferlessAccessCounter;
+  std::chrono::time_point<std::chrono::system_clock> LastAccess;
+
+  void markAccess() noexcept { LastAccess = std::chrono::system_clock::now(); }
 
   /// Marks the current size as the peak of the current zone, if sufficient.
   void mayBePeak() noexcept
   {
     if (Size == 0 || Capacity <= OriginalCapacity)
       return;
 
-    SuccessfulBufferlessAccessCounter.reset();
     if (Size > SizePeaks[CurrentPeakIndex])
       SizePeaks[CurrentPeakIndex] = Size;
   }
@@ -194,15 +166,9 @@ class RingBufferBase
 
     ++CurrentPeakIndex;
     if (CurrentPeakIndex >= SizePeaks.size())
-    {
-      // If reached the end of the measurement, drop half of the measurement
-      // data.
-      auto NewMiddle = std::rotate(SizePeaks.begin(),
-                                   SizePeaks.begin() + SizePeaks.size() / 2 + 1,
-                                   SizePeaks.end());
-      std::fill(NewMiddle, SizePeaks.end(), 0);
-      CurrentPeakIndex = NewMiddle - SizePeaks.begin();
-    }
+      // If we reached the end of the measurement vector, restart from the
+      // start. This is a little ring buffer of itself. :)
+      CurrentPeakIndex = 0;
   }
 };
 

include/core/monomux/server/SessionData.hpp

@@ -67,18 +67,22 @@ class SessionData
   /// the connection towards the session.
   raw_fd getIdentifyingFD() const noexcept;
 
-  /// Reads at most \p Size bytes from the output of the program running in the
-  /// session, if any.
-  std::string readOutput(std::size_t Size);
-
-  /// \returns whether there is buffered output available on the output pipe
-  /// from the session, i.e. further \p readOutput() calls could be made without
-  /// interacting with the underlying device.
-  bool stillHasOutput() noexcept;
-
-  /// Sends the \p Data as input to the program running in the session, if any.
-  /// \returns the number of bytes written.
-  std::size_t sendInput(std::string_view Data);
+  /// \returns the connection through which data can be read from the session,
+  /// if there is any.
+  Pipe* getReader() noexcept
+  {
+    if (!hasProcess() || !getProcess().hasPty())
+      return nullptr;
+    return &getProcess().getPty()->reader();
+  }
+  /// \returns the connection through which data can be sent to the session,
+  /// if there is any.
+  Pipe* getWriter() noexcept
+  {
+    if (!hasProcess() || !getProcess().hasPty())
+      return nullptr;
+    return &getProcess().getPty()->writer();
+  }
 
   const std::vector<ClientData*>& getAttachedClients() const noexcept
   {

include/core/monomux/system/BufferedChannel.hpp

@@ -161,6 +161,11 @@ class BufferedChannel : public Channel
   /// \returns the number of bytes already written but not yet flushed.
   std::size_t writeInBuffer() const noexcept;
 
+  /// Attempts to automatically free auto-growing memory resources associated
+  /// with the buffer(s), if it is possible and deemed meaningful. This is a
+  /// heuristics-based call that does not always actually free resources.
+  void tryFreeResources();
+
 protected:
   UniqueScalar<OpaqueBufferType*, nullptr> Read;
   UniqueScalar<OpaqueBufferType*, nullptr> Write;

src/client/Client.cpp

@@ -234,6 +234,8 @@ void Client::loop()
     if (ExternalEventProcessor)
       // Process "external" events before blocking on "wait()".
       ExternalEventProcessor(*this);
+    ControlSocket.tryFreeResources();
+    DataSocket->tryFreeResources();
 
     const std::size_t NumTriggeredFDs = Poll->wait();
     for (std::size_t I = 0; I < NumTriggeredFDs; ++I)

src/client/Terminal.cpp

@@ -124,6 +124,7 @@ void Terminal::clientInput(Terminal* Term, Client& Client)
 
     Client.sendData(Input);
   } while (Term->input()->hasBufferedRead());
+  Term->input()->tryFreeResources();
 }
 
 void Terminal::clientOutput(Terminal* Term, Client& Client)
@@ -137,6 +138,7 @@ void Terminal::clientOutput(Terminal* Term, Client& Client)
 
   while (Term->output()->hasBufferedWrite())
     Term->output()->flushWrites();
+  Term->output()->tryFreeResources();
 }
 
 void Terminal::clientEventReady(Terminal* Term, Client& Client)

src/server/Server.cpp

@@ -168,15 +168,20 @@ void Server::loop()
       {
         if (auto* Session = std::get_if<SessionConnection>(Entity))
         {
+          SessionData& S = **Session;
           if (Event.Incoming)
+          {
             // First check for data coming from a session. This is the most
             // populous in terms of bandwidth.
-            dataCallback(**Session);
+            dataCallback(S);
+            S.getReader()->tryFreeResources();
+          }
           if (Event.Outgoing)
           {
             try
             {
-              (**Session).sendInput(std::string_view{});
+              S.getWriter()->flushWrites();
+              S.getWriter()->tryFreeResources();
             }
             catch (const buffer_overflow& BO)
             {
@@ -187,22 +192,34 @@ void Server::loop()
         }
         if (auto* Data = std::get_if<ClientDataConnection>(Entity))
         {
+          ClientData& C = **Data;
+          auto ClientID = C.id();
+
           if (Event.Incoming)
             // Second, try to see if the data is coming from a client, like
             // keypresses and such. We expect to see many of these, too.
-            dataCallback(**Data);
+            dataCallback(C);
           if (Event.Outgoing)
-            flushAndReschedule(*Poll, *(**Data).getDataSocket());
+            flushAndReschedule(*Poll, *C.getDataSocket());
+
+          if (Clients.find(ClientID) != Clients.end())
+            C.getDataSocket()->tryFreeResources();
           continue;
         }
         if (auto* Control = std::get_if<ClientControlConnection>(Entity))
         {
+          ClientData& C = **Control;
+          auto ClientID = C.id();
+
           if (Event.Incoming)
             // Lastly, check if the receive is happening on the control
             // connection, where messages are small and far inbetween.
-            controlCallback(**Control);
+            controlCallback(C);
           if (Event.Outgoing)
-            flushAndReschedule(*Poll, (**Control).getControlSocket());
+            flushAndReschedule(*Poll, C.getControlSocket());
+
+          if (Clients.find(ClientID) != Clients.end())
+            C.getControlSocket().tryFreeResources();
           continue;
         }
       }
@@ -394,6 +411,8 @@ void Server::controlCallback(ClientData& Client)
 
   if (ClientSock.hasBufferedRead())
     Poll->schedule(ClientSock.raw(), /* Incoming =*/true, /* Outgoing =*/false);
+  else
+    ClientSock.tryFreeResources();
 
   if (Data.empty())
     return;
@@ -478,7 +497,7 @@ void Server::dataCallback(ClientData& Client)
   if (SessionData* S = Client.getAttachedSession())
     try
     {
-      S->sendInput(Data);
+      S->getWriter()->write(Data);
     }
     catch (const buffer_overflow& BO)
     {
@@ -526,7 +545,7 @@ void Server::dataCallback(SessionData& Session)
   std::string Data;
   try
   {
-    Data = Session.readOutput(BufferSize);
+    Data = Session.getReader()->read(BufferSize);
   }
   catch (const buffer_overflow& BO)
   {
@@ -543,7 +562,7 @@ void Server::dataCallback(SessionData& Session)
     return;
   }
 
-  if (Session.stillHasOutput())
+  if (Session.getReader()->hasBufferedRead())
     Poll->schedule(Session.getIdentifyingFD(),
                    /* Incoming =*/true,
                    /* Outgoing =*/false);

src/server/SessionData.cpp

@@ -45,26 +45,6 @@ raw_fd SessionData::getIdentifyingFD() const noexcept
   return P.getPty()->raw().get();
 }
 
-std::string SessionData::readOutput(std::size_t Size)
-{
-  if (!hasProcess() || !getProcess().hasPty())
-    return {};
-  return getProcess().getPty()->reader().read(Size);
-}
-
-bool SessionData::stillHasOutput() noexcept
-{
-  return hasProcess() && getProcess().getPty() &&
-         getProcess().getPty()->reader().hasBufferedRead();
-}
-
-std::size_t SessionData::sendInput(std::string_view Data)
-{
-  if (!hasProcess() || !getProcess().hasPty())
-    return 0;
-  return getProcess().getPty()->writer().write(Data);
-}
-
 ClientData* SessionData::getLatestClient() const
 {
   MONOMUX_TRACE_LOG(LOG(trace) << "Searching latest active client of \"" << Name