From 92ae4af2a720fff5be223dee392bf7c660f347df Mon Sep 17 00:00:00 2001
From: Badrish Chandramouli <badrishc@microsoft.com>
Date: Tue, 7 Dec 2021 16:28:27 -0800
Subject: [PATCH 1/2] [C#] Add static option to unpin objects when returning to
 SectorAlignedMemoryPool (#606)

* Fix memory leak with bulk flushes during checkpoints.

* Cherry pick fix from v2, for not throwing error when we run out of space in PendingFlushList.

* nit

* change testcase to use lower memory.

* Option to unpin pool objects on return.

* nit

* update comment.

* nit

* formatting
---
 cs/src/core/Utilities/BufferPool.cs | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/cs/src/core/Utilities/BufferPool.cs b/cs/src/core/Utilities/BufferPool.cs
index ae064ef83..525581eed 100644
--- a/cs/src/core/Utilities/BufferPool.cs
+++ b/cs/src/core/Utilities/BufferPool.cs
@@ -123,10 +123,18 @@ public override string ToString()
     public sealed class SectorAlignedBufferPool
     {
         /// <summary>
-        /// Disable buffer pool
+        /// Disable buffer pool.
+        /// This static option should be enabled on program entry, and not modified once FASTER is instantiated.
         /// </summary>
         public static bool Disabled = false;
 
+        /// <summary>
+        /// Unpin objects when they are returned to the pool, so that we do not hold pinned objects long term.
+        /// If set, we will unpin when objects are returned and re-pin when objects are returned from the pool.
+        /// This static option should be enabled on program entry, and not modified once FASTER is instantiated.
+        /// </summary>
+        public static bool UnpinOnReturn = false;
+
         private const int levels = 32;
         private readonly int recordSize;
         private readonly int sectorSize;
@@ -164,7 +172,14 @@ public void Return(SectorAlignedMemory page)
             page.valid_offset = 0;
             Array.Clear(page.buffer, 0, page.buffer.Length);
             if (!Disabled)
+            {
+                if (UnpinOnReturn)
+                {
+                    page.handle.Free();
+                    page.handle = default;
+                }
                 queue[page.level].Enqueue(page);
+            }
             else
             {
                 page.handle.Free();
@@ -210,6 +225,12 @@ public unsafe SectorAlignedMemory Get(int numRecords)
 
             if (!Disabled && queue[index].TryDequeue(out SectorAlignedMemory page))
             {
+                if (UnpinOnReturn)
+                {
+                    page.handle = GCHandle.Alloc(page.buffer, GCHandleType.Pinned);
+                    page.aligned_pointer = (byte*)(((long)page.handle.AddrOfPinnedObject() + (sectorSize - 1)) & ~((long)sectorSize - 1));
+                    page.offset = (int)((long)page.aligned_pointer - (long)page.handle.AddrOfPinnedObject());
+                }
                 return page;
             }
 
@@ -239,7 +260,8 @@ public void Free()
                 if (queue[i] == null) continue;
                 while (queue[i].TryDequeue(out SectorAlignedMemory result))
                 {
-                    result.handle.Free();
+                    if (!UnpinOnReturn)
+                        result.handle.Free();
                     result.buffer = null;
                 }
             }

From 29c8bc642bb4b02b5ae8af473117974dc9b9afd3 Mon Sep 17 00:00:00 2001
From: Badrish Chandramouli <badrishc@microsoft.com>
Date: Tue, 7 Dec 2021 16:37:47 -0800
Subject: [PATCH 2/2] Update home.md

---
 docs/_pages/home.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/_pages/home.md b/docs/_pages/home.md
index 0188146f6..2ad096725 100644
--- a/docs/_pages/home.md
+++ b/docs/_pages/home.md
@@ -10,7 +10,7 @@ header:
       url: "/docs/quick-start-guide/"
 excerpt: >
   A fast concurrent persistent key-value store and log, in C# and C++.<br />
-  <small><a href="https://github.com/microsoft/FASTER/releases/tag/v1.9.6">Latest release v1.9.6</a></small>
+  <small><a href="https://github.com/microsoft/FASTER/releases/tag/v1.9.9">Latest release v1.9.9</a></small>
 features:
   - image_path: /assets/images/faster-feature-1.png
     alt: "feature1"