Put object store memory on /dev/shm on linux (#89)

* put object store memory on /dev/shm on linux

* fix

* fix mac

lib/python/ray/services.py

@@ -147,7 +147,13 @@ def start_objstore(node_ip_address, redis_address, cleanup=True):
   """
   # Compute a fraction of the system memory for the Plasma store to use.
   system_memory = psutil.virtual_memory().total
-  plasma_store_memory = int(system_memory * 0.75)
+  if sys.platform == "linux" or sys.platform == "linux2":
+    # On linux we use /dev/shm, its size is half the size of the physical
+    # memory. To not overflow it, we set the plasma memory limit to 0.4 times
+    # the size of the physical memory.
+    plasma_store_memory = int(system_memory * 0.4)
+  else:
+    plasma_store_memory = int(system_memory * 0.75)
   # Start the Plasma store.
   plasma_store_name, p1 = plasma.start_plasma_store(plasma_store_memory=plasma_store_memory, use_profiler=RUN_PLASMA_STORE_PROFILER)
   # Start the plasma manager.

src/plasma/malloc.c

@@ -68,8 +68,12 @@ int create_buffer(int64_t size) {
                          (DWORD)(uint64_t) size, NULL)) {
     fd = -1;
   }
+#else
+#ifdef __linux__
+  static char template[] = "/dev/shm/plasmaXXXXXX";
 #else
   static char template[] = "/tmp/plasmaXXXXXX";
+#endif
   char file_name[32];
   strncpy(file_name, template, 32);
   fd = mkstemp(file_name);