use only one mmapped file

cpp/src/plasma/store.cc

@@ -905,21 +905,22 @@ class PlasmaStoreRunner {
   PlasmaStoreRunner() {}
 
   void Start(char* socket_name, int64_t system_memory, std::string directory,
-             bool hugepages_enabled, bool use_one_memory_mapped_file) {
+             bool hugepages_enabled) {
     // Create the event loop.
     loop_.reset(new EventLoop);
     store_.reset(
         new PlasmaStore(loop_.get(), system_memory, directory, hugepages_enabled));
     plasma_config = store_->GetPlasmaStoreInfo();
 
-    // If the store is configured to use a single memory-mapped file, then we
-    // achieve that by mallocing and freeing a single large amount of space.
-    // that maximum allowed size up front.
-    if (use_one_memory_mapped_file) {
-      void* pointer = plasma::dlmemalign(kBlockSize, system_memory);
-      ARROW_CHECK(pointer != nullptr);
-      plasma::dlfree(pointer);
-    }
+    // We are using a single memory-mapped file by mallocing and freeing a single
+    // large amount of space up front. According to the documentation,
+    // dlmalloc might need up to 128*sizeof(size_t) bytes for internal
+    // bookkeeping.
+    void* pointer = plasma::dlmemalign(kBlockSize, system_memory - 256 * sizeof(size_t));
+    ARROW_CHECK(pointer != nullptr);
+    // This will unmap the file, but the next one created will be as large
+    // as this one (this is an implementation detail of dlmalloc).
+    plasma::dlfree(pointer);
 
     int socket = BindIpcSock(socket_name, true);
     // TODO(pcm): Check return value.
@@ -955,15 +956,14 @@ void HandleSignal(int signal) {
 }
 
 void StartServer(char* socket_name, int64_t system_memory, std::string plasma_directory,
-                 bool hugepages_enabled, bool use_one_memory_mapped_file) {
+                 bool hugepages_enabled) {
   // Ignore SIGPIPE signals. If we don't do this, then when we attempt to write
   // to a client that has already died, the store could die.
   signal(SIGPIPE, SIG_IGN);
 
   g_runner.reset(new PlasmaStoreRunner());
   signal(SIGTERM, HandleSignal);
-  g_runner->Start(socket_name, system_memory, plasma_directory, hugepages_enabled,
-                  use_one_memory_mapped_file);
+  g_runner->Start(socket_name, system_memory, plasma_directory, hugepages_enabled);
 }
 
 }  // namespace plasma
@@ -975,11 +975,9 @@ int main(int argc, char* argv[]) {
   // Directory where plasma memory mapped files are stored.
   std::string plasma_directory;
   bool hugepages_enabled = false;
-  // True if a single large memory-mapped file should be created at startup.
-  bool use_one_memory_mapped_file = false;
   int64_t system_memory = -1;
   int c;
-  while ((c = getopt(argc, argv, "s:m:d:hf")) != -1) {
+  while ((c = getopt(argc, argv, "s:m:d:h")) != -1) {
     switch (c) {
       case 'd':
         plasma_directory = std::string(optarg);
@@ -994,14 +992,16 @@ int main(int argc, char* argv[]) {
         char extra;
         int scanned = sscanf(optarg, "%" SCNd64 "%c", &system_memory, &extra);
         ARROW_CHECK(scanned == 1);
+        // Set system memory, potentially rounding it to a page size
+        // Also make it so dlmalloc fails if we try to request more memory than
+        // is available.
+        system_memory =
+            plasma::dlmalloc_set_footprint_limit(static_cast<size_t>(system_memory));
         ARROW_LOG(INFO) << "Allowing the Plasma store to use up to "
                         << static_cast<double>(system_memory) / 1000000000
                         << "GB of memory.";
         break;
       }
-      case 'f':
-        use_one_memory_mapped_file = true;
-        break;
       default:
         exit(-1);
     }
@@ -1051,12 +1051,8 @@ int main(int argc, char* argv[]) {
     SetMallocGranularity(1024 * 1024 * 1024);  // 1 GB
   }
 #endif
-  // Make it so dlmalloc fails if we try to request more memory than is
-  // available.
-  plasma::dlmalloc_set_footprint_limit((size_t)system_memory);
   ARROW_LOG(DEBUG) << "starting server listening on " << socket_name;
-  plasma::StartServer(socket_name, system_memory, plasma_directory, hugepages_enabled,
-                      use_one_memory_mapped_file);
+  plasma::StartServer(socket_name, system_memory, plasma_directory, hugepages_enabled);
   plasma::g_runner->Shutdown();
   plasma::g_runner = nullptr;
 

python/pyarrow/plasma.py

@@ -78,7 +78,6 @@ def build_plasma_tensorflow_op():
 @contextlib.contextmanager
 def start_plasma_store(plasma_store_memory,
                        use_valgrind=False, use_profiler=False,
-                       use_one_memory_mapped_file=False,
                        plasma_directory=None, use_hugepages=False):
     """Start a plasma store process.
     Args:
@@ -87,8 +86,6 @@ def start_plasma_store(plasma_store_memory,
             of valgrind. If this is True, use_profiler must be False.
         use_profiler (bool): True if the plasma store should be started inside
             a profiler. If this is True, use_valgrind must be False.
-        use_one_memory_mapped_file: If True, then the store will use only a
-            single memory-mapped file.
         plasma_directory (str): Directory where plasma memory mapped files
             will be stored.
         use_hugepages (bool): True if the plasma store should use huge pages.
@@ -107,8 +104,6 @@ def start_plasma_store(plasma_store_memory,
         command = [plasma_store_executable,
                    "-s", plasma_store_name,
                    "-m", str(plasma_store_memory)]
-        if use_one_memory_mapped_file:
-            command += ["-f"]
         if plasma_directory:
             command += ["-d", plasma_directory]
         if use_hugepages:

python/pyarrow/tests/test_plasma.py

@@ -37,6 +37,7 @@
 
 DEFAULT_PLASMA_STORE_MEMORY = 10 ** 8
 USE_VALGRIND = os.getenv("PLASMA_VALGRIND") == "1"
+SMALL_OBJECT_SIZE = 9000
 
 
 def random_name():
@@ -110,15 +111,11 @@ def assert_get_object_equal(unit_test, client1, client2, object_id,
 class TestPlasmaClient(object):
 
     def setup_method(self, test_method):
-        use_one_memory_mapped_file = (test_method ==
-                                      self.test_use_one_memory_mapped_file)
-
         import pyarrow.plasma as plasma
         # Start Plasma store.
         self.plasma_store_ctx = plasma.start_plasma_store(
             plasma_store_memory=DEFAULT_PLASMA_STORE_MEMORY,
-            use_valgrind=USE_VALGRIND,
-            use_one_memory_mapped_file=use_one_memory_mapped_file)
+            use_valgrind=USE_VALGRIND)
         self.plasma_store_name, self.p = self.plasma_store_ctx.__enter__()
         # Connect to Plasma.
         self.plasma_client = plasma.connect(self.plasma_store_name)
@@ -471,22 +468,26 @@ def assert_create_raises_plasma_full(unit_test, size):
         memory_buffers.append(memory_buffer)
         # Remaining space is 50%. Make sure that we can't create an
         # object of size 50% + 1, but we can create one of size 20%.
-        assert_create_raises_plasma_full(self, 50 * PERCENT + 1)
+        assert_create_raises_plasma_full(
+            self, 50 * PERCENT + SMALL_OBJECT_SIZE)
         _, memory_buffer, _ = create_object(self.plasma_client, 20 * PERCENT)
         del memory_buffer
         _, memory_buffer, _ = create_object(self.plasma_client, 20 * PERCENT)
         del memory_buffer
-        assert_create_raises_plasma_full(self, 50 * PERCENT + 1)
+        assert_create_raises_plasma_full(
+            self, 50 * PERCENT + SMALL_OBJECT_SIZE)
 
         _, memory_buffer, _ = create_object(self.plasma_client, 20 * PERCENT)
         memory_buffers.append(memory_buffer)
         # Remaining space is 30%.
-        assert_create_raises_plasma_full(self, 30 * PERCENT + 1)
+        assert_create_raises_plasma_full(
+            self, 30 * PERCENT + SMALL_OBJECT_SIZE)
 
         _, memory_buffer, _ = create_object(self.plasma_client, 10 * PERCENT)
         memory_buffers.append(memory_buffer)
         # Remaining space is 20%.
-        assert_create_raises_plasma_full(self, 20 * PERCENT + 1)
+        assert_create_raises_plasma_full(
+            self, 20 * PERCENT + SMALL_OBJECT_SIZE)
 
     def test_contains(self):
         fake_object_ids = [random_object_id() for _ in range(100)]
@@ -838,7 +839,7 @@ def test_subscribe_deletions(self):
             assert -1 == recv_dsize
             assert -1 == recv_msize
 
-    def test_use_one_memory_mapped_file(self):
+    def test_use_full_memory(self):
         # Fill the object store up with a large number of small objects and let
         # them go out of scope.
         for _ in range(100):
@@ -851,8 +852,8 @@ def test_use_one_memory_mapped_file(self):
             create_object(self.plasma_client2, DEFAULT_PLASMA_STORE_MEMORY, 0)
         # Verify that an object that is too large does not fit.
         with pytest.raises(pa.lib.PlasmaStoreFull):
-            create_object(self.plasma_client2, DEFAULT_PLASMA_STORE_MEMORY + 1,
-                          0)
+            create_object(self.plasma_client2,
+                          DEFAULT_PLASMA_STORE_MEMORY + SMALL_OBJECT_SIZE, 0)
 
     def test_client_death_during_get(self):
         import pyarrow.plasma as plasma