From fdcbcf701618612dd6509a84464e333744091ded Mon Sep 17 00:00:00 2001
From: Matthew Parkinson <mattpark@microsoft.com>
Date: Tue, 2 Jul 2019 14:06:24 +0100
Subject: [PATCH] Add prefetch to mpscq.

---
 src/ds/bits.h  | 9 +++++++++
 src/ds/mpscq.h | 1 +
 2 files changed, 10 insertions(+)

diff --git a/src/ds/bits.h b/src/ds/bits.h
index f7c3d77..62e6288 100644
--- a/src/ds/bits.h
+++ b/src/ds/bits.h
@@ -136,6 +136,15 @@ namespace snmalloc
 #endif
     }
 
+    inline void prefetch(void* ptr)
+    {
+#if defined(PLATFORM_IS_X86)
+      _mm_prefetch(reinterpret_cast<const char *>(ptr), _MM_HINT_T0);
+#else
+#  warning "Missing pause intrinsic"
+#endif
+    }
+
     inline uint64_t tick()
     {
 #if defined(PLATFORM_IS_X86)
diff --git a/src/ds/mpscq.h b/src/ds/mpscq.h
index 39ee2f9..06b7265 100644
--- a/src/ds/mpscq.h
+++ b/src/ds/mpscq.h
@@ -71,6 +71,7 @@ namespace snmalloc
       if (next != nullptr)
       {
         front = next;
+        bits::prefetch(&(next->next));
         assert(front);
         std::atomic_thread_fence(std::memory_order_acquire);
         invariant();