diff --git a/applications/test/processorTopology/Make/files b/applications/test/processorTopology/Make/files
new file mode 100644
index 0000000000..c9d5a6bbe0
--- /dev/null
+++ b/applications/test/processorTopology/Make/files
@@ -0,0 +1,3 @@
+Test-processorTopology.C
+
+EXE = $(FOAM_USER_APPBIN)/Test-processorTopology
diff --git a/applications/test/processorTopology/Make/options b/applications/test/processorTopology/Make/options
new file mode 100644
index 0000000000..18e6fe47af
--- /dev/null
+++ b/applications/test/processorTopology/Make/options
@@ -0,0 +1,2 @@
+/* EXE_INC = */
+/* EXE_LIBS = */
diff --git a/applications/test/processorTopology/Test-processorTopology.C b/applications/test/processorTopology/Test-processorTopology.C
new file mode 100644
index 0000000000..1d8d7fab1a
--- /dev/null
+++ b/applications/test/processorTopology/Test-processorTopology.C
@@ -0,0 +1,113 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2022 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+Description
+    Test/output processor topology
+
+\*---------------------------------------------------------------------------*/
+
+#include "argList.H"
+#include "Time.H"
+#include "polyMesh.H"
+#include "globalMeshData.H"
+#include "OFstream.H"
+
+using namespace Foam;
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+// Main program:
+
+int main(int argc, char *argv[])
+{
+    argList::noFunctionObjects();
+    argList::addNote
+    (
+        "Create a metis graph file representation for an OpenFOAM mesh"
+    );
+
+    #include "setRootCase.H"
+
+    if (!Pstream::parRun())
+    {
+        FatalErrorInFunction
+            << "Only meaningful in parallel"
+            << exit(FatalError);
+    }
+
+    #include "createTime.H"
+    #include "createPolyMesh.H"
+
+    const globalMeshData& globData = mesh.globalData();
+
+    const labelListList& connectivity = globData;
+
+    if (Pstream::master())
+    {
+        OFstream os("processorTopology.dot");
+
+        os << "// processorTopology" << nl << nl;
+        os.beginBlock("graph");
+
+        forAll(connectivity, proci)
+        {
+            label nconn = 0;
+
+            for (const label neighProci : connectivity[proci])
+            {
+                if (proci < neighProci)
+                {
+                    if (nconn++)
+                    {
+                        os << "  ";
+                    }
+                    else
+                    {
+                        os << indent;
+                    }
+                    os << proci << " -- " << neighProci;
+                }
+            }
+
+            if (nconn)
+            {
+                os  << nl;
+            }
+        }
+
+        os.endBlock();
+
+        Info<< "Wrote processorTopology graph: "
+            << runTime.relativePath(os.name()) << nl;
+
+        Info<< nl
+            << "Use neato, circo or fdp graphviz tools" << nl;
+    }
+
+    Info<< nl << "End\n" << endl;
+
+    return 0;
+}
+
+// ************************************************************************* //
diff --git a/applications/utilities/parallelProcessing/redistributePar/parLagrangianRedistributor.C b/applications/utilities/parallelProcessing/redistributePar/parLagrangianRedistributor.C
index 73eaf42958..e7e0bfe0fd 100644
--- a/applications/utilities/parallelProcessing/redistributePar/parLagrangianRedistributor.C
+++ b/applications/utilities/parallelProcessing/redistributePar/parLagrangianRedistributor.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2015 OpenFOAM Foundation
-    Copyright (C) 2015-2018 OpenCFD Ltd.
+    Copyright (C) 2015-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -185,9 +185,8 @@ Foam::parLagrangianRedistributor::redistributeLagrangianPositions
     }
 
 
-    // Start sending. Sets number of bytes transferred
-    labelList allNTrans(Pstream::nProcs());
-    pBufs.finishedSends(allNTrans);
+    // Start sending
+    pBufs.finishedSends();
 
 
     {
@@ -205,18 +204,15 @@ Foam::parLagrangianRedistributor::redistributeLagrangianPositions
             IDLList<passivePositionParticle>()
         );
 
-
         // Retrieve from receive buffers
-        forAll(allNTrans, procI)
+        for (const int proci : pBufs.allProcs())
         {
-            const label nRec = allNTrans[procI];
+            //Pout<< "Receive from processor" << proci << " : "
+            //    << pBufs.hasRecvData(proci) << endl;
 
-            //Pout<< "From processor " << procI << " receiving bytes " << nRec
-            //    << endl;
-
-            if (nRec)
+            if (pBufs.hasRecvData(proci))
             {
-                UIPstream particleStream(procI, pBufs);
+                UIPstream particleStream(proci, pBufs);
 
                 // Receive particles and locate them
                 IDLList<passivePositionParticle> newParticles
diff --git a/src/OpenFOAM/db/IOobjects/decomposedBlockData/decomposedBlockData.C b/src/OpenFOAM/db/IOobjects/decomposedBlockData/decomposedBlockData.C
index f91e5d83a9..0c05da957a 100644
--- a/src/OpenFOAM/db/IOobjects/decomposedBlockData/decomposedBlockData.C
+++ b/src/OpenFOAM/db/IOobjects/decomposedBlockData/decomposedBlockData.C
@@ -394,8 +394,7 @@ bool Foam::decomposedBlockData::readBlocks
             }
         }
 
-        labelList recvSizes;
-        pBufs.finishedSends(recvSizes);
+        pBufs.finishedSends();
 
         if (!UPstream::master(comm))
         {
@@ -524,8 +523,7 @@ Foam::autoPtr<Foam::ISstream> Foam::decomposedBlockData::readBlocks
             ok = is.good();
         }
 
-        labelList recvSizes;
-        pBufs.finishedSends(recvSizes);
+        pBufs.finishedSends();
 
         if (!UPstream::master(comm))
         {
diff --git a/src/OpenFOAM/db/IOstreams/Pstreams/PstreamBuffers.C b/src/OpenFOAM/db/IOstreams/Pstreams/PstreamBuffers.C
index e2f73c5e03..07e7eccc49 100644
--- a/src/OpenFOAM/db/IOstreams/Pstreams/PstreamBuffers.C
+++ b/src/OpenFOAM/db/IOstreams/Pstreams/PstreamBuffers.C
@@ -33,10 +33,11 @@ License
 void Foam::PstreamBuffers::finalExchange
 (
     labelList& recvSizes,
-    const bool block
+    const bool wait
 )
 {
     // Could also check that it is not called twice
+    // but that is used for overlapping send/recv (eg, overset)
     finishedSendsCalled_ = true;
 
     if (commsType_ == UPstream::commsTypes::nonBlocking)
@@ -51,7 +52,7 @@ void Foam::PstreamBuffers::finalExchange
             recvBuf_,
             tag_,
             comm_,
-            block
+            wait
         );
     }
 }
@@ -62,10 +63,11 @@ void Foam::PstreamBuffers::finalExchange
     const labelUList& sendProcs,
     const labelUList& recvProcs,
     labelList& recvSizes,
-    const bool block
+    const bool wait
 )
 {
     // Could also check that it is not called twice
+    // but that is used for overlapping send/recv (eg, overset)
     finishedSendsCalled_ = true;
 
     if (commsType_ == UPstream::commsTypes::nonBlocking)
@@ -87,7 +89,7 @@ void Foam::PstreamBuffers::finalExchange
             recvBuf_,
             tag_,
             comm_,
-            block
+            wait
         );
     }
 }
@@ -104,6 +106,7 @@ Foam::PstreamBuffers::PstreamBuffers
 )
 :
     finishedSendsCalled_(false),
+    allowClearRecv_(true),
     format_(fmt),
     commsType_(commsType),
     tag_(tag),
@@ -151,20 +154,107 @@ void Foam::PstreamBuffers::clear()
 }
 
 
-void Foam::PstreamBuffers::finishedSends(const bool block)
+void Foam::PstreamBuffers::clearStorage()
+{
+    // Could also clear out entire sendBuf_, recvBuf_ and reallocate.
+    // Not sure if it makes much difference
+    for (DynamicList<char>& buf : sendBuf_)
+    {
+        buf.clearStorage();
+    }
+    for (DynamicList<char>& buf : recvBuf_)
+    {
+        buf.clearStorage();
+    }
+    recvBufPos_ = 0;
+
+    finishedSendsCalled_ = false;
+}
+
+
+bool Foam::PstreamBuffers::hasSendData() const
+{
+    for (const DynamicList<char>& buf : sendBuf_)
+    {
+        if (!buf.empty())
+        {
+            return true;
+        }
+    }
+    return false;
+}
+
+
+bool Foam::PstreamBuffers::hasSendData(const label proci) const
+{
+    return !sendBuf_[proci].empty();
+}
+
+
+bool Foam::PstreamBuffers::hasRecvData() const
+{
+    if (finishedSendsCalled_)
+    {
+        for (const DynamicList<char>& buf : recvBuf_)
+        {
+            if (!buf.empty())
+            {
+                return true;
+            }
+        }
+    }
+    #ifdef FULLDEBUG
+    else
+    {
+        FatalErrorInFunction
+            << "Call finishedSends first" << exit(FatalError);
+    }
+    #endif
+
+    return false;
+}
+
+
+bool Foam::PstreamBuffers::hasRecvData(const label proci) const
+{
+    if (finishedSendsCalled_)
+    {
+        return !recvBuf_[proci].empty();
+    }
+    #ifdef FULLDEBUG
+    else
+    {
+        FatalErrorInFunction
+            << "Call finishedSends first" << exit(FatalError);
+    }
+    #endif
+
+    return false;
+}
+
+
+bool Foam::PstreamBuffers::allowClearRecv(bool on) noexcept
+{
+    bool old(allowClearRecv_);
+    allowClearRecv_ = on;
+    return old;
+}
+
+
+void Foam::PstreamBuffers::finishedSends(const bool wait)
 {
     labelList recvSizes;
-    finalExchange(recvSizes, block);
+    finalExchange(recvSizes, wait);
 }
 
 
 void Foam::PstreamBuffers::finishedSends
 (
     labelList& recvSizes,
-    const bool block
+    const bool wait
 )
 {
-    finalExchange(recvSizes, block);
+    finalExchange(recvSizes, wait);
 
     if (commsType_ != UPstream::commsTypes::nonBlocking)
     {
@@ -184,11 +274,11 @@ void Foam::PstreamBuffers::finishedSends
 (
     const labelUList& sendProcs,
     const labelUList& recvProcs,
-    const bool block
+    const bool wait
 )
 {
     labelList recvSizes;
-    finalExchange(sendProcs, recvProcs, recvSizes, block);
+    finalExchange(sendProcs, recvProcs, recvSizes, wait);
 }
 
 
@@ -197,10 +287,10 @@ void Foam::PstreamBuffers::finishedSends
     const labelUList& sendProcs,
     const labelUList& recvProcs,
     labelList& recvSizes,
-    const bool block
+    const bool wait
 )
 {
-    finalExchange(sendProcs, recvProcs, recvSizes, block);
+    finalExchange(sendProcs, recvProcs, recvSizes, wait);
 
     if (commsType_ != UPstream::commsTypes::nonBlocking)
     {
diff --git a/src/OpenFOAM/db/IOstreams/Pstreams/PstreamBuffers.H b/src/OpenFOAM/db/IOstreams/Pstreams/PstreamBuffers.H
index 193567813b..2fec28c518 100644
--- a/src/OpenFOAM/db/IOstreams/Pstreams/PstreamBuffers.H
+++ b/src/OpenFOAM/db/IOstreams/Pstreams/PstreamBuffers.H
@@ -90,7 +90,7 @@ class PstreamBuffers
 {
     // Friendship
     friend class UOPstreamBase;  // Access to sendBuf_
-    friend class UIPstreamBase;  // Access to recvBuf_ recvBufPos_;
+    friend class UIPstreamBase;  // Access to recvBuf_, recvBufPos_
 
 
     // Private Data
@@ -98,6 +98,9 @@ class PstreamBuffers
         //- Track if sends are complete
         bool finishedSendsCalled_;
 
+        //- Permit clear of individual receive buffer by external access
+        bool allowClearRecv_;
+
         //- Buffer format (ascii | binary)
         const IOstreamOption::streamFormat format_;
 
@@ -110,30 +113,31 @@ class PstreamBuffers
         //- Communicator
         const label comm_;
 
-        //- Send buffer
+        //- Send buffer. Size is nProcs()
         List<DynamicList<char>> sendBuf_;
 
-        //- Receive buffer
+        //- Receive buffer. Size is nProcs()
         List<DynamicList<char>> recvBuf_;
 
-        //- Current read positions within recvBuf_
+        //- Current read positions within recvBuf_. Size is nProcs()
         labelList recvBufPos_;
 
 
     // Private Member Functions
 
         //- Mark all sends as having been done.
-        //  This will start receives in non-blocking mode.
-        void finalExchange(labelList& recvSizes, const bool block);
+        //  This will start receives (nonBlocking comms).
+        void finalExchange(labelList& recvSizes, const bool wait);
 
-        //- Mark all sends as having been done.
-        //  Only exchange sizes between sendProcs/recvProcs
+        //- Mark sends as done.
+        //  Only exchange sizes using the sendProcs/recvProcs subset
+        //  (nonBlocking comms).
         void finalExchange
         (
             const labelUList& sendProcs,
             const labelUList& recvProcs,
             labelList& recvSizes,
-            const bool block
+            const bool wait
         );
 
 
@@ -183,54 +187,157 @@ public:
             return comm_;
         }
 
-        //- True if finishedSends has been called
+
+    // Sizing
+
+        //- Number of ranks associated with PstreamBuffers
+        label nProcs() const noexcept
+        {
+            return recvBufPos_.size();
+        }
+
+        //- Range of ranks indices associated with PstreamBuffers
+        UPstream::rangeType allProcs() const noexcept
+        {
+            // Proc 0 -> nProcs (int value)
+            return UPstream::rangeType(static_cast<int>(nProcs()));
+        }
+
+
+    // Queries
+
+        //- True if finishedSends() or finishedNeighbourSends() has been called
         bool finished() const noexcept
         {
             return finishedSendsCalled_;
         }
 
+        //- True if any (local) send buffers have data
+        bool hasSendData() const;
+
+        //- True if (local) send buffer has data on specified processor.
+        bool hasSendData(const label proci) const;
+
+        //- True if any (local) recv buffers have data.
+        //- Must call finishedSends() or finishedNeighbourSends() first!
+        bool hasRecvData() const;
+
+        //- True if (local) recv buffer has data on specified processor.
+        //- Must call finishedSends() or finishedNeighbourSends() first!
+        bool hasRecvData(const label proci) const;
+
+        //- Is clearStorage of individual receive buffer by external hooks
+        //- allowed? (default: true)
+        bool allowClearRecv() const noexcept
+        {
+            return allowClearRecv_;
+        }
+
 
     // Edit
 
-        //- Reset (clear) individual buffers and reset state.
-        //  Does not clear buffer storage
+        //- Clear individual buffers and reset states.
+        //  Does not clear individual buffer storage.
         void clear();
 
+        //- Clear individual buffer storage and reset states.
+        void clearStorage();
+
+        //- Change allowClearRecv, return previous value
+        bool allowClearRecv(bool on) noexcept;
+
 
     // Functions
 
-        //- Mark all sends as having been done.
-        //  This will start receives in non-blocking mode.
-        //  If block will wait for all transfers to finish
-        //  (only relevant for nonBlocking mode)
-        void finishedSends(const bool block = true);
+        //- Mark sends as done
+        //
+        //  Non-blocking mode: populates receive buffers (all-to-all).
+        //  \param wait wait for requests to complete (in nonBlocking mode)
+        void finishedSends(const bool wait = true);
 
-        //- Mark all sends as having been done.
-        //  Same as above but also returns sizes (bytes) received.
-        //  \note currently only valid for non-blocking.
-        void finishedSends(labelList& recvSizes, const bool block = true);
+        //- Mark sends as done.
+        //- Recovers the sizes (bytes) received.
+        //
+        //  Non-blocking mode: populates receive buffers (all-to-all).
+        //  \param[out] recvSizes the sizes (bytes) received
+        //  \param wait wait for requests to complete (in nonBlocking mode)
+        //
+        //  \warning currently only valid for nonBlocking comms.
+        void finishedSends(labelList& recvSizes, const bool wait = true);
 
-        //- Mark all sends as having been done, with limited
-        //- send/recv processor connections.
-        //  \note currently only valid for non-blocking.
+        //- Mark sends as done using subset of send/recv ranks
+        //- to exchange data on.
+        //
+        //  Non-blocking mode: populates receive buffers.
+        //  \param sendProcs ranks used for sends
+        //  \param recvProcs ranks used for recvs
+        //  \param wait wait for requests to complete (in nonBlocking mode)
+        //
+        //  \warning currently only valid for nonBlocking comms.
         void finishedSends
         (
             const labelUList& sendProcs,
             const labelUList& recvProcs,
-            const bool block = true
+            const bool wait = true
         );
 
-        //- Mark all sends as having been done, with limited
-        //- send/recv processor connections.
-        //  Same as above but also returns sizes (bytes) received.
-        //  \note currently only valid for non-blocking.
+        //- Mark sends as done using subset of send/recv ranks
+        //- to exchange data on. Recovers the sizes (bytes) received.
+        //
+        //  Non-blocking mode: populates receive buffers.
+        //
+        //  \param sendProcs ranks used for sends
+        //  \param recvProcs ranks used for recvs
+        //  \param[out] recvSizes the sizes (bytes) received
+        //  \param wait wait for requests to complete (in nonBlocking mode)
+        //
+        //  \warning currently only valid for nonBlocking comms.
         void finishedSends
         (
             const labelUList& sendProcs,
             const labelUList& recvProcs,
             labelList& recvSizes,
-            const bool block = true
+            const bool wait = true
         );
+
+        //- Mark sends as done using subset of send/recv ranks
+        //- and recover the sizes (bytes) received.
+        //
+        //  Non-blocking mode: populates receive buffers.
+        //
+        //  \param neighProcs ranks used for sends/recvs
+        //  \param wait wait for requests to complete (in nonBlocking mode)
+        //
+        //  \warning currently only valid for nonBlocking comms.
+        //  \note Same as finishedSends with identical sendProcs/recvProcs
+        void finishedNeighbourSends
+        (
+            const labelUList& neighProcs,
+            const bool wait = true
+        )
+        {
+            finishedSends(neighProcs, neighProcs, wait);
+        }
+
+        //- Mark sends as done using subset of send/recv ranks
+        //- and recover the sizes (bytes) received.
+        //
+        //  Non-blocking mode: it will populate receive buffers.
+        //
+        //  \param neighProcs ranks used for sends/recvs
+        //  \param[out] recvSizes the sizes (bytes) received
+        //  \param wait wait for requests to complete (in nonBlocking mode)
+        //
+        //  \warning currently only valid for nonBlocking mode.
+        void finishedNeighbourSends
+        (
+            const labelUList& neighProcs,
+            labelList& recvSizes,
+            const bool wait = true
+        )
+        {
+            finishedSends(neighProcs, neighProcs, recvSizes, wait);
+        }
 };
 
 
diff --git a/src/OpenFOAM/db/IOstreams/Pstreams/UIPstreamBase.C b/src/OpenFOAM/db/IOstreams/Pstreams/UIPstreamBase.C
index e7d8266f32..e733ba8124 100644
--- a/src/OpenFOAM/db/IOstreams/Pstreams/UIPstreamBase.C
+++ b/src/OpenFOAM/db/IOstreams/Pstreams/UIPstreamBase.C
@@ -184,7 +184,7 @@ Foam::UIPstreamBase::UIPstreamBase
     recvBufPos_(buffers.recvBufPos_[fromProcNo]),
     tag_(buffers.tag()),
     comm_(buffers.comm()),
-    clearAtEnd_(true),
+    clearAtEnd_(buffers.allowClearRecv()),
     messageSize_(0)
 {
     if
diff --git a/src/OpenFOAM/meshes/polyMesh/syncTools/syncToolsTemplates.C b/src/OpenFOAM/meshes/polyMesh/syncTools/syncToolsTemplates.C
index bbbf34f0ad..9f16a7c17b 100644
--- a/src/OpenFOAM/meshes/polyMesh/syncTools/syncToolsTemplates.C
+++ b/src/OpenFOAM/meshes/polyMesh/syncTools/syncToolsTemplates.C
@@ -127,7 +127,7 @@ void Foam::syncTools::syncPointMap
 
     if (Pstream::parRun())
     {
-        DynamicList<label> sendRecvProcs;
+        DynamicList<label> neighbProcs;
         PstreamBuffers pBufs(Pstream::commsTypes::nonBlocking);
 
         // Send
@@ -159,14 +159,14 @@ void Foam::syncTools::syncPointMap
                     }
                 }
 
-                sendRecvProcs.append(nbrProci);
+                neighbProcs.append(nbrProci);
                 UOPstream toNbr(nbrProci, pBufs);
                 toNbr << patchInfo;
             }
         }
 
         // Limit exchange to involved procs
-        pBufs.finishedSends(sendRecvProcs, sendRecvProcs);
+        pBufs.finishedNeighbourSends(neighbProcs);
 
         // Receive and combine.
         for (const polyPatch& pp : patches)
@@ -370,7 +370,7 @@ void Foam::syncTools::syncEdgeMap
 
     if (Pstream::parRun())
     {
-        DynamicList<label> sendRecvProcs;
+        DynamicList<label> neighbProcs;
         PstreamBuffers pBufs(Pstream::commsTypes::nonBlocking);
 
         // Send
@@ -404,14 +404,14 @@ void Foam::syncTools::syncEdgeMap
                     }
                 }
 
-                sendRecvProcs.append(nbrProci);
+                neighbProcs.append(nbrProci);
                 UOPstream toNbr(nbrProci, pBufs);
                 toNbr << patchInfo;
             }
         }
 
         // Limit exchange to involved procs
-        pBufs.finishedSends(sendRecvProcs, sendRecvProcs);
+        pBufs.finishedNeighbourSends(neighbProcs);
 
 
         // Receive and combine.
@@ -1102,7 +1102,7 @@ void Foam::syncTools::syncBoundaryFaceList
         }
         else
         {
-            DynamicList<label> sendRecvProcs;
+            DynamicList<label> neighbProcs;
             PstreamBuffers pBufs(Pstream::commsTypes::nonBlocking);
 
             // Send
@@ -1122,14 +1122,14 @@ void Foam::syncTools::syncBoundaryFaceList
                         pp.start()-boundaryOffset
                     );
 
-                    sendRecvProcs.append(nbrProci);
+                    neighbProcs.append(nbrProci);
                     UOPstream toNbr(nbrProci, pBufs);
                     toNbr << fld;
                 }
             }
 
             // Limit exchange to involved procs
-            pBufs.finishedSends(sendRecvProcs, sendRecvProcs);
+            pBufs.finishedNeighbourSends(neighbProcs);
 
 
             // Receive and combine.
diff --git a/src/OpenFOAM/parallel/globalIndex/globalIndexTemplates.C b/src/OpenFOAM/parallel/globalIndex/globalIndexTemplates.C
index ee1df113aa..5634d802e3 100644
--- a/src/OpenFOAM/parallel/globalIndex/globalIndexTemplates.C
+++ b/src/OpenFOAM/parallel/globalIndex/globalIndexTemplates.C
@@ -871,15 +871,14 @@ void Foam::globalIndex::get
             UOPstream os(proci, sendBufs);
             os << localIDs;
         }
-        labelList recvSizes;
-        sendBufs.finishedSends(recvSizes);
+        sendBufs.finishedSends();
 
 
         PstreamBuffers returnBufs(Pstream::commsTypes::nonBlocking, tag, comm);
 
-        forAll(recvSizes, proci)
+        for (const int proci : sendBufs.allProcs())
         {
-            if (recvSizes[proci])
+            if (sendBufs.hasRecvData(proci))
             {
                 UIPstream is(proci, sendBufs);
                 labelList localIDs(is);
diff --git a/src/finiteVolume/fvMesh/zoneDistribute/zoneDistribute.C b/src/finiteVolume/fvMesh/zoneDistribute/zoneDistribute.C
index d676291170..bd600b1fb5 100644
--- a/src/finiteVolume/fvMesh/zoneDistribute/zoneDistribute.C
+++ b/src/finiteVolume/fvMesh/zoneDistribute/zoneDistribute.C
@@ -171,7 +171,6 @@ void Foam::zoneDistribute::setUpCommforZone
 
 
         PstreamBuffers pBufs(UPstream::commsTypes::nonBlocking);
-        labelList recvSizes;
 
         // Stream data into buffer
         for (const int proci : UPstream::allProcs())
@@ -205,12 +204,12 @@ void Foam::zoneDistribute::setUpCommforZone
 
         if (returnReduce(fullUpdate, orOp<bool>()))
         {
-            pBufs.finishedSends(recvSizes);
+            pBufs.finishedSends();
 
             // Update which ones receive
             for (const int proci : UPstream::allProcs())
             {
-                recvFrom_[proci] = (recvSizes[proci] > 0);
+                recvFrom_[proci] = pBufs.hasRecvData(proci);
             }
         }
         else
@@ -233,18 +232,14 @@ void Foam::zoneDistribute::setUpCommforZone
             }
 
             // Wait until everything is written
-            pBufs.finishedSends(sendProcs, recvProcs, recvSizes);
+            pBufs.finishedSends(sendProcs, recvProcs);
         }
 
         for (const int proci : UPstream::allProcs())
         {
             send_[proci].clear();
 
-            if
-            (
-                proci != UPstream::myProcNo()
-             && recvFrom_[proci]   // Or: (recvSizes[proci] > 0)
-            )
+            if (proci != UPstream::myProcNo() && pBufs.hasRecvData(proci))
             {
                 UIPstream fromProc(proci, pBufs);
                 fromProc >> send_[proci];
diff --git a/src/finiteVolume/fvMesh/zoneDistribute/zoneDistributeI.H b/src/finiteVolume/fvMesh/zoneDistribute/zoneDistributeI.H
index 81b33c565b..e709dde4bb 100644
--- a/src/finiteVolume/fvMesh/zoneDistribute/zoneDistributeI.H
+++ b/src/finiteVolume/fvMesh/zoneDistribute/zoneDistributeI.H
@@ -191,7 +191,6 @@ Foam::Map<Type> Foam::zoneDistribute::getDatafromOtherProc
 
 
         PstreamBuffers pBufs(UPstream::commsTypes::nonBlocking);
-        labelList recvSizes;
 
         // Stream data into buffer
         for (const int proci : UPstream::allProcs())
@@ -222,13 +221,13 @@ Foam::Map<Type> Foam::zoneDistribute::getDatafromOtherProc
                 }
             }
 
-            pBufs.finishedSends(sendProcs, recvProcs, recvSizes);
+            pBufs.finishedSends(sendProcs, recvProcs);
         }
         else
         {
             // Fallback to all-to-all communication
 
-            pBufs.finishedSends(recvSizes);
+            pBufs.finishedSends();
         }
 
 
@@ -237,11 +236,7 @@ Foam::Map<Type> Foam::zoneDistribute::getDatafromOtherProc
             // Do not use recvFrom_[proci] here
             // - could be incorrect if comms are not prepared!
 
-            if
-            (
-                proci != UPstream::myProcNo()
-             && (recvSizes[proci] > 0)
-            )
+            if (proci != UPstream::myProcNo() && pBufs.hasRecvData(proci))
             {
                 UIPstream fromProc(proci, pBufs);
                 Map<Type> tmpValue(fromProc);
diff --git a/src/functionObjects/randomProcesses/energySpectrum/energySpectrum.C b/src/functionObjects/randomProcesses/energySpectrum/energySpectrum.C
index fb8f794b98..d918de3e4b 100644
--- a/src/functionObjects/randomProcesses/energySpectrum/energySpectrum.C
+++ b/src/functionObjects/randomProcesses/energySpectrum/energySpectrum.C
@@ -223,7 +223,7 @@ bool Foam::functionObjects::energySpectrum::write()
     {
         PstreamBuffers pBufs(Pstream::commsTypes::nonBlocking);
 
-        UOPstream toProc(0, pBufs);
+        UOPstream toProc(Pstream::masterNo(), pBufs);
 
         toProc << Uc << C << cellAddr_;
 
diff --git a/src/functionObjects/utilities/syncObjects/syncObjects.C b/src/functionObjects/utilities/syncObjects/syncObjects.C
index 9e90dff60f..3376f5ff6c 100644
--- a/src/functionObjects/utilities/syncObjects/syncObjects.C
+++ b/src/functionObjects/utilities/syncObjects/syncObjects.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2020-2021 OpenCFD Ltd.
+    Copyright (C) 2020-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -96,8 +96,7 @@ void Foam::functionObjects::syncObjects::sync()
     );
 
 
-    const label nProcs = Pstream::nProcs(pBufs.comm());
-    for (label proci = 0; proci < nProcs; proci++)
+    for (const int proci : pBufs.allProcs())
     {
         // Get database to send
         const objectRegistry& sendObr = mappedPatchBase::subRegistry
@@ -123,7 +122,7 @@ void Foam::functionObjects::syncObjects::sync()
     // Start sending and receiving and block
     pBufs.finishedSends();
 
-    for (label proci = 0; proci < nProcs; proci++)
+    for (const int proci : pBufs.allProcs())
     {
         // Get database to receive data into
         const objectRegistry& receiveObr = mappedPatchBase::subRegistry
diff --git a/src/lagrangian/basic/Cloud/Cloud.C b/src/lagrangian/basic/Cloud/Cloud.C
index 47aeafeb71..6210cb23e4 100644
--- a/src/lagrangian/basic/Cloud/Cloud.C
+++ b/src/lagrangian/basic/Cloud/Cloud.C
@@ -286,34 +286,18 @@ void Foam::Cloud<ParticleType>::move
         }
 
 
-        // Start sending. Sets number of bytes transferred
-        labelList allNTrans(Pstream::nProcs());
-        pBufs.finishedSends(allNTrans);
+        pBufs.finishedSends();
 
-
-        bool transferred = false;
-
-        for (const label n : allNTrans)
-        {
-            if (n)
-            {
-                transferred = true;
-                break;
-            }
-        }
-        reduce(transferred, orOp<bool>());
-
-        if (!transferred)
+        if (!returnReduce(pBufs.hasRecvData(), orOp<bool>()))
         {
+            // No parcels to transfer
             break;
         }
 
         // Retrieve from receive buffers
         for (const label neighbProci : neighbourProcs)
         {
-            label nRec = allNTrans[neighbProci];
-
-            if (nRec)
+            if (pBufs.hasRecvData(neighbProci))
             {
                 UIPstream particleStream(neighbProci, pBufs);
 
diff --git a/src/lagrangian/intermediate/submodels/Kinematic/PatchInteractionModel/RecycleInteraction/RecycleInteraction.C b/src/lagrangian/intermediate/submodels/Kinematic/PatchInteractionModel/RecycleInteraction/RecycleInteraction.C
index 4bdac8dd0a..6a88b20256 100644
--- a/src/lagrangian/intermediate/submodels/Kinematic/PatchInteractionModel/RecycleInteraction/RecycleInteraction.C
+++ b/src/lagrangian/intermediate/submodels/Kinematic/PatchInteractionModel/RecycleInteraction/RecycleInteraction.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -254,29 +254,18 @@ void Foam::RecycleInteraction<CloudType>::postEvolve()
             }
         }
 
-        // Start sending. Sets number of bytes transferred
-        labelList allNTrans(Pstream::nProcs());
-        pBufs.finishedSends(allNTrans);
-        bool transferred = false;
-        for (const label n : allNTrans)
-        {
-            if (n)
-            {
-                transferred = true;
-                break;
-            }
-        }
-        reduce(transferred, orOp<bool>());
-        if (!transferred)
+        pBufs.finishedSends();
+
+        if (!returnReduce(pBufs.hasRecvData(), orOp<bool>()))
         {
             // No parcels to transfer
             return;
         }
 
         // Retrieve from receive buffers
-        for (label proci = 0; proci < Pstream::nProcs(); ++proci)
+        for (const int proci : pBufs.allProcs())
         {
-            if (allNTrans[proci])
+            if (pBufs.hasRecvData(proci))
             {
                 UIPstream particleStream(proci, pBufs);
                 IDLList<parcelType> newParticles
diff --git a/src/parallel/reconstruct/faReconstruct/faMeshReconstructor.C b/src/parallel/reconstruct/faReconstruct/faMeshReconstructor.C
index 2651d82be9..73d90d8362 100644
--- a/src/parallel/reconstruct/faReconstruct/faMeshReconstructor.C
+++ b/src/parallel/reconstruct/faReconstruct/faMeshReconstructor.C
@@ -162,7 +162,7 @@ void Foam::faMeshReconstructor::calcAddressing
         {
             labelList localOrder;
 
-            UIPstream fromProc(Pstream::master(), pBufs);
+            UIPstream fromProc(Pstream::masterNo(), pBufs);
             fromProc >> localOrder;
 
             faFaceProcAddr_ = labelList(faFaceProcAddr_, localOrder);
diff --git a/src/randomProcesses/noise/noiseModels/surfaceNoise/surfaceNoise.C b/src/randomProcesses/noise/noiseModels/surfaceNoise/surfaceNoise.C
index fa0f3bada3..b6129ad0b0 100644
--- a/src/randomProcesses/noise/noiseModels/surfaceNoise/surfaceNoise.C
+++ b/src/randomProcesses/noise/noiseModels/surfaceNoise/surfaceNoise.C
@@ -182,7 +182,7 @@ void surfaceNoise::readSurfaceData
             pBufs.finishedSends();
 
             // Receive data from the master
-            UIPstream fromProc(0, pBufs);
+            UIPstream fromProc(Pstream::masterNo(), pBufs);
 
             scalarList pSlice(fromProc);
 
@@ -260,7 +260,7 @@ scalar surfaceNoise::writeSurfaceData
 
         if (!Pstream::master())
         {
-            UOPstream toProc(0, pBufs);
+            UOPstream toProc(Pstream::masterNo(), pBufs);
             toProc << data;
         }
 
@@ -375,7 +375,7 @@ scalar surfaceNoise::surfaceAverage
 
         if (!Pstream::master())
         {
-            UOPstream toProc(0, pBufs);
+            UOPstream toProc(Pstream::masterNo(), pBufs);
             toProc << data;
         }
 
diff --git a/src/sampling/meshToMesh/meshToMeshParallelOps.C b/src/sampling/meshToMesh/meshToMeshParallelOps.C
index 71e89311a5..6f47496b5d 100644
--- a/src/sampling/meshToMesh/meshToMeshParallelOps.C
+++ b/src/sampling/meshToMesh/meshToMeshParallelOps.C
@@ -304,8 +304,6 @@ void Foam::meshToMesh::distributeCells
     List<labelList>& procLocalFaceIDs
 ) const
 {
-    PstreamBuffers pBufs(Pstream::commsTypes::nonBlocking);
-
     points.setSize(Pstream::nProcs());
     nInternalFaces.setSize(Pstream::nProcs(), 0);
     faces.setSize(Pstream::nProcs());
@@ -317,6 +315,8 @@ void Foam::meshToMesh::distributeCells
     procLocalFaceIDs.setSize(Pstream::nProcs());;
 
 
+    PstreamBuffers pBufs(Pstream::commsTypes::nonBlocking);
+
     for (const int domain : Pstream::allProcs())
     {
         const labelList& sendElems = map.subMap()[domain];
diff --git a/src/transportModels/geometricVoF/advectionSchemes/isoAdvection/isoAdvection.C b/src/transportModels/geometricVoF/advectionSchemes/isoAdvection/isoAdvection.C
index 145962b805..c046107dc3 100644
--- a/src/transportModels/geometricVoF/advectionSchemes/isoAdvection/isoAdvection.C
+++ b/src/transportModels/geometricVoF/advectionSchemes/isoAdvection/isoAdvection.C
@@ -497,7 +497,7 @@ Foam::DynamicList<Foam::label>  Foam::isoAdvection::syncProcPatches
 
     if (Pstream::parRun())
     {
-        DynamicList<label> sendRecvProcs;
+        DynamicList<label> neighProcs;
         PstreamBuffers pBufs(Pstream::commsTypes::nonBlocking);
 
         // Send
@@ -507,7 +507,7 @@ Foam::DynamicList<Foam::label>  Foam::isoAdvection::syncProcPatches
                 refCast<const processorPolyPatch>(patches[patchi]);
             const label nbrProci = procPatch.neighbProcNo();
 
-            sendRecvProcs.append(nbrProci);
+            neighProcs.append(nbrProci);
             UOPstream toNbr(nbrProci, pBufs);
 
             const scalarField& pFlux = dVf.boundaryField()[patchi];
@@ -523,8 +523,8 @@ Foam::DynamicList<Foam::label>  Foam::isoAdvection::syncProcPatches
             toNbr << surfCellFacesOnProcPatch << dVfPatch;
         }
 
-        // Limit exchange to involved procs
-        pBufs.finishedSends(sendRecvProcs, sendRecvProcs);
+        // Limited to involved neighbour procs
+        pBufs.finishedNeighbourSends(neighProcs);
 
 
         // Receive and combine