diff --git a/src/coreclr/src/gc/satori/SatoriAllocator.cpp b/src/coreclr/src/gc/satori/SatoriAllocator.cpp
index af6a3349476..a1265e9944b 100644
--- a/src/coreclr/src/gc/satori/SatoriAllocator.cpp
+++ b/src/coreclr/src/gc/satori/SatoriAllocator.cpp
@@ -37,7 +37,7 @@ tryAgain:
     SatoriRegion* putBack = nullptr;
 
     int bucket = SizeToBucket(regionSize);
-    SatoriRegion* region = m_queues[bucket]->TryRemove(regionSize, putBack);
+    SatoriRegion* region = m_queues[bucket]->TryRemoveWithSize(regionSize, putBack);
     if (region)
     {
         if (putBack)
@@ -50,7 +50,7 @@ tryAgain:
 
     while (++bucket < Satori::BUCKET_COUNT)
     {
-        region = m_queues[bucket]->TryPop(regionSize, putBack);
+        region = m_queues[bucket]->TryPopWithSize(regionSize, putBack);
         if (region)
         {
             if (putBack)
@@ -184,7 +184,7 @@ SatoriObject* SatoriAllocator::AllocRegular(SatoriAllocationContext* context, si
             //       also need to release this _after_ using it since work is done here already
             //       may also try smoothing, although unlikely.
             //       All this can be tuned once full GC works.
-            size_t desiredFreeSpace = max(size, Satori::REGION_SIZE_GRANULARITY * 1 / 10);
+            size_t desiredFreeSpace = max(size, Satori::REGION_SIZE_GRANULARITY * 9 / 10);
             if (region->ThreadLocalCompact(desiredFreeSpace))
             {
                 // we have enough free space in the region to continue
diff --git a/src/coreclr/src/gc/satori/SatoriGC.cpp b/src/coreclr/src/gc/satori/SatoriGC.cpp
index 8c169e8a872..b4284327aa6 100644
--- a/src/coreclr/src/gc/satori/SatoriGC.cpp
+++ b/src/coreclr/src/gc/satori/SatoriGC.cpp
@@ -237,7 +237,25 @@ unsigned SatoriGC::GetGcCount()
 
 bool SatoriGC::IsThreadUsingAllocationContextHeap(gc_alloc_context* acontext, int thread_number)
 {
-    __UNREACHABLE();
+    // TODO: VS should prefer when running on the same core as recorded in alloc region, if present.
+    //       negative thread_number could indicate "do not care"
+    //       also need to assign numbers to threads when scanning.
+    //       at very least there is dependency on 0 being unique.
+    while (true)
+    {
+        int threadScanCount = acontext->alloc_count;
+        int currentScanCount = m_heap->Recycler()->GetScanCount();
+        if (threadScanCount >= currentScanCount)
+        {
+            break;
+        }
+
+        if (Interlocked::CompareExchange(&acontext->alloc_count, currentScanCount, threadScanCount) == threadScanCount)
+        {
+            return true;
+        }
+    }
+
     return false;
 }
 
diff --git a/src/coreclr/src/gc/satori/SatoriGC.h b/src/coreclr/src/gc/satori/SatoriGC.h
index 50b999a5764..8cd818f8029 100644
--- a/src/coreclr/src/gc/satori/SatoriGC.h
+++ b/src/coreclr/src/gc/satori/SatoriGC.h
@@ -20,8 +20,6 @@ class SatoriGC : public IGCHeapInternal
 private:
     int64_t m_perfCounterFrequency;
     SatoriHeap* m_heap;
-    SatoriAllocator* m_allocator;
-    SatoriRecycler* m_recycler;
 
     // what is the difference between these two?
     // should these be volatile
diff --git a/src/coreclr/src/gc/satori/SatoriMarkChunk.h b/src/coreclr/src/gc/satori/SatoriMarkChunk.h
index 34514c30944..d9a521f8ed6 100644
--- a/src/coreclr/src/gc/satori/SatoriMarkChunk.h
+++ b/src/coreclr/src/gc/satori/SatoriMarkChunk.h
@@ -50,6 +50,11 @@ public:
             nullptr;
     }
 
+    size_t Count()
+    {
+        return m_top;
+    }
+
 private:
     size_t m_top;
 
diff --git a/src/coreclr/src/gc/satori/SatoriObject.inl b/src/coreclr/src/gc/satori/SatoriObject.inl
index 76268a43f75..45ba99cfcb7 100644
--- a/src/coreclr/src/gc/satori/SatoriObject.inl
+++ b/src/coreclr/src/gc/satori/SatoriObject.inl
@@ -178,6 +178,7 @@ inline void SatoriObject::ClearNextInMarkStack()
 }
 
 // TODO: VS same as [Get|Set]NextInMarkStack
+// TODO: VS rename GetLocalReloc
 inline int32_t SatoriObject::GetReloc()
 {
     return ((int32_t*)this)[-2];
diff --git a/src/coreclr/src/gc/satori/SatoriQueue.h b/src/coreclr/src/gc/satori/SatoriQueue.h
index a960e9e9244..b40b576cc04 100644
--- a/src/coreclr/src/gc/satori/SatoriQueue.h
+++ b/src/coreclr/src/gc/satori/SatoriQueue.h
@@ -18,12 +18,12 @@ class SatoriQueue
 public:
 
     SatoriQueue() :
-        m_lock(), m_head(), m_tail()
+        m_lock(), m_head(), m_tail(), m_count()
     {
         m_lock.Initialize();
     };
 
-    void Push(T* item)
+    int Push(T* item)
     {
         SatoriLockHolder<SatoriLock> holder(&m_lock);
         item->m_containingQueue = this;
@@ -38,6 +38,8 @@ public:
             m_head->m_prev = item;
             m_head = item;
         }
+
+        return ++m_count;
     }
 
     T* TryPop()
@@ -51,6 +53,7 @@ public:
                 return nullptr;
             }
 
+            m_count--;
             result->m_containingQueue = nullptr;
             m_head = result->m_next;
             if (m_head == nullptr)
@@ -72,6 +75,7 @@ public:
     void Enqueue(T* item)
     {
         SatoriLockHolder<SatoriLock> holder(&m_lock);
+        m_count++;
         item->m_containingQueue = this;
         if (m_tail == nullptr)
         {
@@ -95,6 +99,7 @@ public:
                 return false;
             }
 
+            m_count--;
             item->m_containingQueue = nullptr;
             if (item->m_prev == nullptr)
             {
@@ -125,20 +130,16 @@ public:
         return item->m_containingQueue == this;
     }
 
-    bool CanPop()
+    int Count()
     {
-        return m_head != nullptr;
-    }
-
-    bool CanDequeue()
-    {
-        return m_tail != nullptr;
+        return m_count;
     }
 
 protected:
     SatoriLock m_lock;
     T* m_head;
     T* m_tail;
+    int m_count;
 };
 
 #endif
diff --git a/src/coreclr/src/gc/satori/SatoriRecycler.cpp b/src/coreclr/src/gc/satori/SatoriRecycler.cpp
index 98ad431fa5c..d3407cb4084 100644
--- a/src/coreclr/src/gc/satori/SatoriRecycler.cpp
+++ b/src/coreclr/src/gc/satori/SatoriRecycler.cpp
@@ -12,6 +12,8 @@
 
 #include "SatoriHeap.h"
 #include "SatoriRecycler.h"
+#include "SatoriObject.h"
+#include "SatoriObject.inl"
 #include "SatoriRegion.h"
 #include "SatoriRegion.inl"
 #include "SatoriMarkChunk.h"
@@ -20,9 +22,12 @@ void SatoriRecycler::Initialize(SatoriHeap* heap)
 {
     m_heap = heap;
 
-    m_regions = new SatoriRegionQueue();
-    m_work_list = new SatoriMarkChunkQueue();
-    m_free_list = new SatoriMarkChunkQueue();
+    m_allRegions = new SatoriRegionQueue();
+    m_stayingRegions = new SatoriRegionQueue();
+    m_relocatingRegions = new SatoriRegionQueue();
+
+    m_workList = new SatoriMarkChunkQueue();
+    m_freeList = new SatoriMarkChunkQueue();
 
     SatoriRegion* region = m_heap->Allocator()->GetRegion(Satori::REGION_SIZE_GRANULARITY);
 
@@ -35,7 +40,7 @@ void SatoriRecycler::Initialize(SatoriHeap* heap)
         }
 
         SatoriMarkChunk* chunk = SatoriMarkChunk::InitializeAt(mem);
-        m_free_list->Push(chunk);
+        m_freeList->Push(chunk);
     }
 }
 
@@ -45,8 +50,282 @@ void SatoriRecycler::AddRegion(SatoriRegion* region)
 
     // TODO: VS verify
 
+    // TODO: VS volatile?
     region->Publish();
-    // TODO: VS leak the region for now
 
-    // TODO: VS for now count and once have 5, lets mark.
+    int count = m_allRegions->Push(region);
+    if (count > 10)
+    {
+        Collect();
+    }
+}
+
+void SatoriRecycler::Collect()
+{
+    // mark own stack into work queues
+    IncrementScanCount();
+    MarkOwnStack();
+
+    // TODO: VS perhaps drain queues as a part of MarkOwnStack? - to give other threads chance to self-mark?
+    //       thread marking is fast though, so it may not help a lot.
+
+    // TODO: VS we should not be calling Suspend from multiple threads for the same collect event.
+    //       Perhaps lock and send other threads away, they will suspend soon enough.
+
+    // stop other threads. (except this one, it shoud not be considered a cooperative thread while it is busy doing GC).
+    bool wasCoop = GCToEEInterface::EnablePreemptiveGC();
+    _ASSERTE(wasCoop);
+    GCToEEInterface::SuspendEE(SUSPEND_FOR_GC);
+
+    // TODO: VS this also scans statics. Do we want this?
+    MarkOtherStacks();
+
+    // drain queues
+    DrainMarkQueues();
+
+    // mark handles to queues
+
+    // while have work
+    // {
+    //     drain queues
+    //     mark through SATB cards   (could be due to overflow)
+    // }
+
+    // all marked here 
+
+    // TODO: VS can't know live size without scanning all live objects. We need to scan at least live ones.
+    // Then we could as well coalesce gaps and thread to buckets.
+    // What to do with finalizables?
+
+    // plan regions:
+    // 0% - return to recycler
+    // > 80%   go to stayers   (scan for finalizable one day, if occupancy reduced and has finalizable, this can be done after releasing VM.)
+    // > 50% or with pins - targets, sweep and thread gaps, slice and release free tails, add to queues,   need buckets similar to allocator, should regs have buckets?
+    //   targets go to stayers too.
+    //
+    // rest - add to move sources
+    SatoriRegion* curReg;
+    while (curReg = m_allRegions->TryPop())
+    {
+        m_stayingRegions->Push(curReg);
+    }
+
+    // once no more regs in queue
+    // go through sources and relocate to destinations,
+    // grab empties if no space, add to stayers and use as if gotten from free buckets.
+    // if no space at all, put the reg to stayers. (scan for finalizable one day)
+
+    // go through roots and update refs
+
+    // go through stayers, update refs  (need to care about relocated in stayers, could happen if no space)
+    while (curReg = m_stayingRegions->TryPop())
+    {
+        curReg->CleanMarks();
+        m_allRegions->Push(curReg);
+    }
+
+    // restart VM
+    GCToEEInterface::RestartEE(true);
+
+    // return source regs to allocator.
+
+    // become coop again (note - could block here, it is ok)
+    GCToEEInterface::DisablePreemptiveGC();
+}
+
+class MarkContext
+{
+    friend class SatoriRecycler;
+
+public:
+    MarkContext(SatoriRecycler* recycler)
+        : m_markChunk()
+    {
+        m_recycler = recycler;
+    }
+
+    void PushToMarkQueues(SatoriObject* o)
+    {
+        if (m_markChunk && m_markChunk->TryPush(o))
+        {
+            return;
+        }
+
+        m_recycler->PushToMarkQueuesSlow(m_markChunk, o);
+    }
+
+private:
+    SatoriRecycler* m_recycler;
+    SatoriMarkChunk* m_markChunk;
+};
+
+void SatoriRecycler::PushToMarkQueuesSlow(SatoriMarkChunk* &currentMarkChunk, SatoriObject* o)
+{
+    if (currentMarkChunk)
+    {
+        m_workList->Push(currentMarkChunk);
+    }
+
+    currentMarkChunk = m_freeList->TryPop();
+    if (currentMarkChunk)
+    {
+        bool pushed = currentMarkChunk->TryPush(o);
+        _ASSERTE(pushed);
+    }
+    else
+    {
+        // TODO: VS mark card table
+        o->SetEscaped();
+    }
+}
+
+void SatoriRecycler::MarkFn(PTR_PTR_Object ppObject, ScanContext* sc, uint32_t flags)
+{
+    size_t location = (size_t)*ppObject;
+    if (location == 0)
+    {
+        return;
+    }
+
+    SatoriObject* o = SatoriObject::At(location);
+    if (flags & GC_CALL_INTERIOR)
+    {
+        o = o->ContainingRegion()->FindObject(location);
+        if (o == nullptr)
+        {
+            return;
+        }
+    }
+
+    if (!o->IsMarked())
+    {
+        // TODO: VS should use threadsafe variant
+        o->SetMarked();
+
+        MarkContext* context = (MarkContext*)sc->_unused1;
+        // TODO: VS we do not need to push if card is marked, we will have to revisit anyways.
+        context->PushToMarkQueues(o);
+    }
+
+    if (flags & GC_CALL_PINNED)
+    {
+        o->SetPinned();
+    }
+};
+
+void SatoriRecycler::MarkOwnStack()
+{
+    gc_alloc_context* aContext = GCToEEInterface::GetAllocContext();
+
+    // TODO: VS can this be more robust in case the thread gets stuck?
+    // claim our own stack for scanning
+    while (true)
+    {
+        int threadScanCount = aContext->alloc_count;
+        int currentScanCount = GetScanCount();
+        if (threadScanCount >= currentScanCount)
+        {
+            return;
+        }
+
+        if (Interlocked::CompareExchange(&aContext->alloc_count, currentScanCount, threadScanCount) == threadScanCount)
+        {
+            break;
+        }
+    }
+
+    // mark roots for the current stack
+    ScanContext sc;
+    sc.promotion = TRUE;
+
+    MarkContext c = MarkContext(this);
+    sc._unused1 = &c;
+    GCToEEInterface::GcScanCurrentStackRoots((promote_func*)MarkFn, &sc);
+
+    if (c.m_markChunk != nullptr)
+    {
+        m_workList->Push(c.m_markChunk);
+    }
+}
+
+void SatoriRecycler::MarkOtherStacks()
+{
+    // mark roots for the current stack
+    ScanContext sc;
+    sc.promotion = TRUE;
+
+    MarkContext c = MarkContext(this);
+    sc._unused1 = &c;
+
+    //TODO: VS there should be only one thread with "thread_number == 0"
+    //TODO: VS implement two-pass scheme with preferred vs. any stacks
+
+    GCToEEInterface::GcScanRoots((promote_func*)MarkFn, 2, 2, &sc);
+
+    if (c.m_markChunk != nullptr)
+    {
+        m_workList->Push(c.m_markChunk);
+    }
+}
+
+// TODO: VS interlocked?
+void SatoriRecycler::IncrementScanCount()
+{
+    m_scanCount++;
+}
+
+// TODO: VS volatile?
+inline int SatoriRecycler::GetScanCount()
+{
+    return m_scanCount;
+}
+
+void SatoriRecycler::DrainMarkQueues()
+{
+    SatoriMarkChunk* srcChunk = m_workList->TryPop();
+    SatoriMarkChunk* dstChunk = nullptr;
+    while (srcChunk)
+    {
+        // drain srcChunk to dst chunk
+        SatoriObject* o;
+        while (o = srcChunk->TryPop())
+        {
+            o->ForEachObjectRef(
+                [&](SatoriObject** ref)
+                {
+                    SatoriObject* child = *ref;
+                    if (child && !child->IsMarked())
+                    {
+                        child->SetMarked();
+                        if (!dstChunk || !dstChunk->TryPush(child))
+                        {
+                            this->PushToMarkQueuesSlow(dstChunk, child);
+                        }
+                    }
+                }
+            );
+        }
+
+        // done with srcChunk
+        // if we have nonempty dstChunk (i.e. produced more work),
+        // swap src and dst and continue
+        if (dstChunk && dstChunk->Count() > 0)
+        {
+            SatoriMarkChunk* tmp = srcChunk;
+            _ASSERTE(tmp->Count() == 0);
+            srcChunk = dstChunk;
+            dstChunk = tmp;
+        }
+        else
+        {
+            m_freeList->Push(srcChunk);
+            srcChunk = m_workList->TryPop();
+        }
+    }
+
+    if (dstChunk)
+    {
+        _ASSERTE(dstChunk->Count() == 0);
+        m_freeList->Push(dstChunk);
+    }
 }
diff --git a/src/coreclr/src/gc/satori/SatoriRecycler.h b/src/coreclr/src/gc/satori/SatoriRecycler.h
index 3dc671b4cb2..99543ca2a48 100644
--- a/src/coreclr/src/gc/satori/SatoriRecycler.h
+++ b/src/coreclr/src/gc/satori/SatoriRecycler.h
@@ -18,16 +18,34 @@ class SatoriRegion;
 
 class SatoriRecycler
 {
+    friend class MarkContext;
+
 public:
     void Initialize(SatoriHeap* heap);
     void AddRegion(SatoriRegion* region);
 
+    int GetScanCount();
+
 private:
     SatoriHeap* m_heap;
 
-    SatoriRegionQueue* m_regions;
-    SatoriMarkChunkQueue* m_work_list;
-    SatoriMarkChunkQueue* m_free_list;
+    // used to ensure each thread is scanned once per scan round.
+    int m_scanCount;
+
+    SatoriRegionQueue* m_allRegions;
+    SatoriRegionQueue* m_stayingRegions;
+    SatoriRegionQueue* m_relocatingRegions;
+
+    SatoriMarkChunkQueue* m_workList;
+    SatoriMarkChunkQueue* m_freeList;
+
+    void Collect();
+    static void MarkFn(PTR_PTR_Object ppObject, ScanContext* sc, uint32_t flags);
+    void PushToMarkQueuesSlow(SatoriMarkChunk*& currentMarkChunk, SatoriObject* o);
+    void MarkOwnStack();
+    void MarkOtherStacks();
+    void IncrementScanCount();
+    void DrainMarkQueues();
 };
 
 #endif
diff --git a/src/coreclr/src/gc/satori/SatoriRegion.cpp b/src/coreclr/src/gc/satori/SatoriRegion.cpp
index 0bf3f5492b6..c1f9b88774c 100644
--- a/src/coreclr/src/gc/satori/SatoriRegion.cpp
+++ b/src/coreclr/src/gc/satori/SatoriRegion.cpp
@@ -908,6 +908,11 @@ bool SatoriRegion::ThreadLocalCompact(size_t desiredFreeSpace)
     return (foundFree >= desiredFreeSpace + Satori::MIN_FREE_SIZE || foundFree == desiredFreeSpace);
 }
 
+void SatoriRegion::CleanMarks()
+{
+    ZeroMemory(&m_bitmap[BITMAP_START], (BITMAP_SIZE - BITMAP_START) * sizeof(size_t));
+}
+
 void SatoriRegion::Verify()
 {
 #ifdef _DEBUG
diff --git a/src/coreclr/src/gc/satori/SatoriRegion.h b/src/coreclr/src/gc/satori/SatoriRegion.h
index 1877879590e..0ae97c6f6c1 100644
--- a/src/coreclr/src/gc/satori/SatoriRegion.h
+++ b/src/coreclr/src/gc/satori/SatoriRegion.h
@@ -64,6 +64,8 @@ public:
     SatoriObject* NextMarked(SatoriObject* after);
     bool ThreadLocalCompact(size_t desiredFreeSpace);
 
+    void CleanMarks();
+
     void Verify();
 
 private:
diff --git a/src/coreclr/src/gc/satori/SatoriRegionQueue.cpp b/src/coreclr/src/gc/satori/SatoriRegionQueue.cpp
index 884b6d2d068..2101bb3edbb 100644
--- a/src/coreclr/src/gc/satori/SatoriRegionQueue.cpp
+++ b/src/coreclr/src/gc/satori/SatoriRegionQueue.cpp
@@ -15,7 +15,7 @@
 #include "SatoriRegion.h"
 #include "SatoriRegion.inl"
 
-SatoriRegion* SatoriRegionQueue::TryPop(size_t regionSize, SatoriRegion*& putBack)
+SatoriRegion* SatoriRegionQueue::TryPopWithSize(size_t regionSize, SatoriRegion*& putBack)
 {
     m_lock.Enter();
 
@@ -78,7 +78,7 @@ SatoriRegion* SatoriRegionQueue::TryPop(size_t regionSize, SatoriRegion*& putBac
     return result;
 }
 
-SatoriRegion* SatoriRegionQueue::TryRemove(size_t regionSize, SatoriRegion*& putBack)
+SatoriRegion* SatoriRegionQueue::TryRemoveWithSize(size_t regionSize, SatoriRegion*& putBack)
 {
     m_lock.Enter();
 
diff --git a/src/coreclr/src/gc/satori/SatoriRegionQueue.h b/src/coreclr/src/gc/satori/SatoriRegionQueue.h
index 105db1bb68e..8297f3a151b 100644
--- a/src/coreclr/src/gc/satori/SatoriRegionQueue.h
+++ b/src/coreclr/src/gc/satori/SatoriRegionQueue.h
@@ -17,8 +17,8 @@ class SatoriRegion;
 class SatoriRegionQueue : public SatoriQueue<SatoriRegion>
 {
 public:
-    SatoriRegion* TryPop(size_t regionSize, SatoriRegion* &putBack);
-    SatoriRegion* TryRemove(size_t regionSize, SatoriRegion*& putBack);
+    SatoriRegion* TryPopWithSize(size_t regionSize, SatoriRegion* &putBack);
+    SatoriRegion* TryRemoveWithSize(size_t regionSize, SatoriRegion*& putBack);
 };
 
 #endif
diff --git a/src/coreclr/vm/appdomain.cpp b/src/coreclr/vm/appdomain.cpp
index 9372e79dafc..833a3088437 100644
--- a/src/coreclr/vm/appdomain.cpp
+++ b/src/coreclr/vm/appdomain.cpp
@@ -1349,7 +1349,7 @@ void SystemDomain::LazyInitGlobalStringLiteralMap()
 
     _ASSERTE(GCHeapUtilities::IsGCInProgress() &&
              GCHeapUtilities::IsServerHeap()   &&
-             IsGCSpecialThread());
+             (IsGCSpecialThread() || !GetThread()->PreemptiveGCDisabled()));
 
     SystemDomain* sysDomain = SystemDomain::System();
     if (sysDomain)
@@ -5064,7 +5064,7 @@ void AppDomain::EnumStaticGCRefs(promote_func* fn, ScanContext* sc)
 
     _ASSERTE(GCHeapUtilities::IsGCInProgress() &&
              GCHeapUtilities::IsServerHeap()   &&
-             IsGCSpecialThread());
+            (IsGCSpecialThread() || !GetThread()->PreemptiveGCDisabled()));
 
 #ifndef CROSSGEN_COMPILE
     if (m_pLargeHeapHandleTable != nullptr)