Cycles: Add support for P2P memory distribution (e.g. via NVLink)

This change modifies the multi-device implementation to support memory distribution
across devices, to reduce the overall memory footprint of large scenes and allow scenes to
fit entirely into combined GPU memory that previously had to fall back to host memory.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D7426

1 files changed, 13 insertions, 0 deletions

diff --git a/intern/cycles/device/device.h b/intern/cycles/device/device.h
index c55dfb3a83b..dff981080a5 100644
--- a/intern/cycles/device/device.h
+++ b/intern/cycles/device/device.h
@@ -82,6 +82,7 @@ class DeviceInfo {
   bool has_osl;                      /* Support Open Shading Language. */
   bool use_split_kernel;             /* Use split or mega kernel. */
   bool has_profiling;                /* Supports runtime collection of profiling info. */
+  bool has_peer_memory;              /* GPU has P2P access to memory of another GPU. */
   int cpu_threads;
   vector<DeviceInfo> multi_devices;
   vector<DeviceInfo> denoising_devices;
@@ -99,6 +100,7 @@ class DeviceInfo {
     has_osl = false;
     use_split_kernel = false;
     has_profiling = false;
+    has_peer_memory = false;
   }
 
   bool operator==(const DeviceInfo &info)
@@ -435,6 +437,17 @@ class Device {
   {
   }
 
+  virtual bool is_resident(device_ptr /*key*/, Device *sub_device)
+  {
+    /* Memory is always resident if this is not a multi device, regardless of whether the pointer
+     * is valid or not (since it may not have been allocated yet). */
+    return sub_device == this;
+  }
+  virtual bool check_peer_access(Device * /*peer_device*/)
+  {
+    return false;
+  }
+
   /* static */
   static Device *create(DeviceInfo &info,
                         Stats &stats,