Add the API to trim physical memory footprint (#1638)

- Fixes #1630
- Fixes #1620

Signed-off-by: Tao He <linzhu.ht@alibaba-inc.com>

python/client.cc

@@ -486,6 +486,14 @@ void bind_client(py::module& mod) {
       .def(
           "clear", [](ClientBase* self) { throw_on_error(self->Clear()); },
           doc::ClientBase_clear)
+      .def(
+          "memory_trim",
+          [](ClientBase* self) -> bool {
+            bool trimmed = false;
+            throw_on_error(self->MemoryTrim(trimmed));
+            return trimmed;
+          },
+          doc::ClientBase_memory_trim)
       .def(
           "label",
           [](ClientBase* self, ObjectID id, std::string const& key,

python/pybind11_docs.cc

@@ -773,6 +773,16 @@ const char* ClientBase_clear = R"doc(
 Drop all objects that visible to the current instance in the vineyard cluster.
 )doc";
 
+const char* ClientBase_memory_trim = R"doc(
+.. method:: memory_trim() -> bool
+    :noindex:
+
+Trim the memory pool inside the shared memory allocator to return the unused
+physical memory back to the OS kernel, like the `malloc_trim` API from glibc.
+
+Returns True if it actually released any memory.
+)doc";
+
 const char* ClientBase_reset = R"doc(
 .. method:: reset() -> None
     :noindex:

python/pybind11_docs.h

@@ -105,6 +105,7 @@ extern const char* ClientBase_list_names;
 extern const char* ClientBase_drop_name;
 extern const char* ClientBase_sync_meta;
 extern const char* ClientBase_clear;
+extern const char* ClientBase_memory_trim;
 extern const char* ClientBase_reset;
 extern const char* ClientBase_connected;
 extern const char* ClientBase_instance_id;

python/vineyard/core/tests/test_client.py

@@ -281,3 +281,43 @@ def start_requests(rs, state, ipc_socket):
         r, message = rs.get(block=True)
         if not r:
             pytest.fail(message)
+
+
+def parse_shared_memory_usage():
+    '''Parse the shared memory usage from /proc/meminfo, in KB.'''
+    with open('/proc/meminfo', 'r', encoding='utf-8') as f:
+        lines = f.readlines()
+    for line in lines:
+        if line.startswith('Shmem:'):
+            parts = line.split()
+            return int(parts[1])
+
+
+def test_memory_trim(vineyard_client):
+    data = np.ones((1000, 1000, 16))
+
+    # cleanup the instance
+    vineyard_client.clear()
+    vineyard_client.memory_trim()
+
+    original_memory_usage = parse_shared_memory_usage()
+
+    data = np.ones((1000, 1000, 16))
+    data_kbytes = data.nbytes / 1024
+
+    rs = []
+    for i in range(8):
+        r = vineyard_client.put(data)
+        rs.append(r)
+        current_memory_usage = parse_shared_memory_usage()
+        assert current_memory_usage >= original_memory_usage + i * data_kbytes
+
+    for r in rs:
+        vineyard_client.delete(r)
+
+    current_memory_usage = parse_shared_memory_usage()
+    assert current_memory_usage >= original_memory_usage + (8 - 1) * data_kbytes
+
+    vineyard_client.memory_trim()
+    # there might be some fragmentation overhead
+    assert parse_shared_memory_usage() <= original_memory_usage + 1 * data_kbytes

src/client/client_base.cc

@@ -366,6 +366,17 @@ Status ClientBase::Clear() {
   return Status::OK();
 }
 
+Status ClientBase::MemoryTrim(bool& trimmed) {
+  ENSURE_CONNECTED(this);
+  std::string message_out;
+  WriteMemoryTrimRequest(message_out);
+  RETURN_ON_ERROR(doWrite(message_out));
+  json message_in;
+  RETURN_ON_ERROR(doRead(message_in));
+  RETURN_ON_ERROR(ReadMemoryTrimReply(message_in, trimmed));
+  return Status::OK();
+}
+
 Status ClientBase::Label(const ObjectID object, std::string const& key,
                          std::string const& value) {
   ENSURE_CONNECTED(this);

src/client/client_base.h

@@ -423,6 +423,13 @@ class ClientBase {
    */
   Status Clear();
 
+  /**
+   * @brief Trim the memory pool inside the shared memory allocator to return
+   *        the unused physical memory back to the OS kernel, like the
+   *        `malloc_trim` API from glibc.
+   */
+  Status MemoryTrim(bool& trimmed);
+
   /**
    * @brief Associate given labels to an existing object.
    *

src/common/memory/payload.h

@@ -69,6 +69,8 @@ struct Payload {
 
   bool operator==(const Payload& other) const;
 
+  inline ObjectID id() const { return object_id; }
+
   inline void Reset() { is_sealed = false, is_owner = true; }
 
   inline void MarkAsSealed() { is_sealed = true; }
@@ -162,6 +164,8 @@ struct PlasmaPayload : public Payload {
             (plasma_id == other.plasma_id) && (data_size == other.data_size));
   }
 
+  inline PlasmaID id() const { return plasma_id; }
+
   Payload ToNormalPayload() const {
     return Payload(object_id, data_size, pointer, store_fd, arena_fd, map_size,
                    data_offset);

src/common/util/env.cc

@@ -249,14 +249,14 @@ int64_t get_maximum_shared_memory() {
  * @brief Return the memory size in human readable way.
  */
 std::string prettyprint_memory_size(size_t nbytes) {
-  if (nbytes > (1L << 40)) {
-    return std::to_string(nbytes * 1.0 / (1L << 40)) + " TB";
-  } else if (nbytes > (1L << 30)) {
-    return std::to_string(nbytes * 1.0 / (1L << 30)) + " GB";
-  } else if (nbytes > (1L << 20)) {
-    return std::to_string(nbytes * 1.0 / (1L << 20)) + " MB";
-  } else if (nbytes > (1L << 10)) {
-    return std::to_string(nbytes * 1.0 / (1L << 10)) + " KB";
+  if (nbytes >= (1LL << 40)) {
+    return std::to_string(nbytes * 1.0 / (1LL << 40)) + " TB";
+  } else if (nbytes >= (1LL << 30)) {
+    return std::to_string(nbytes * 1.0 / (1LL << 30)) + " GB";
+  } else if (nbytes >= (1LL << 20)) {
+    return std::to_string(nbytes * 1.0 / (1LL << 20)) + " MB";
+  } else if (nbytes >= (1LL << 10)) {
+    return std::to_string(nbytes * 1.0 / (1LL << 10)) + " KB";
   } else {
     return std::to_string(nbytes) + " B";
   }

src/common/util/protocols.cc

@@ -123,6 +123,8 @@ const std::string command_t::LABEL_REQUEST = "label_request";
 const std::string command_t::LABEL_REPLY = "label_reply";
 const std::string command_t::CLEAR_REQUEST = "clear_request";
 const std::string command_t::CLEAR_REPLY = "clear_reply";
+const std::string command_t::MEMORY_TRIM_REQUEST = "memory_trim_request";
+const std::string command_t::MEMORY_TRIM_REPLY = "memory_trim_reply";
 
 // Stream APIs
 const std::string command_t::CREATE_STREAM_REQUEST = "create_stream_request";
@@ -1301,6 +1303,33 @@ Status ReadClearReply(const json& root) {
   CHECK_IPC_ERROR(root, command_t::CLEAR_REPLY);
   return Status::OK();
 }
+
+void WriteMemoryTrimRequest(std::string& msg) {
+  json root;
+  root["type"] = command_t::MEMORY_TRIM_REQUEST;
+
+  encode_msg(root, msg);
+}
+
+Status ReadMemoryTrimRequest(const json& root) {
+  CHECK_IPC_ERROR(root, command_t::MEMORY_TRIM_REQUEST);
+  return Status::OK();
+}
+
+void WriteMemoryTrimReply(const bool trimmed, std::string& msg) {
+  json root;
+  root["type"] = command_t::MEMORY_TRIM_REPLY;
+  root["trimmed"] = trimmed;
+
+  encode_msg(root, msg);
+}
+
+Status ReadMemoryTrimReply(const json& root, bool& trimmed) {
+  CHECK_IPC_ERROR(root, command_t::MEMORY_TRIM_REPLY);
+  trimmed = root.value("trimmed", false);
+  return Status::OK();
+}
+
 void WriteCreateStreamRequest(const ObjectID& object_id, std::string& msg) {
   json root;
   root["type"] = command_t::CREATE_STREAM_REQUEST;

src/common/util/protocols.h

@@ -99,6 +99,8 @@ struct command_t {
   static const std::string LABEL_REPLY;
   static const std::string CLEAR_REQUEST;
   static const std::string CLEAR_REPLY;
+  static const std::string MEMORY_TRIM_REQUEST;
+  static const std::string MEMORY_TRIM_REPLY;
 
   // Stream APIs
   static const std::string CREATE_STREAM_REQUEST;
@@ -516,6 +518,14 @@ void WriteClearReply(std::string& msg);
 
 Status ReadClearReply(const json& root);
 
+void WriteMemoryTrimRequest(std::string& msg);
+
+Status ReadMemoryTrimRequest(const json& root);
+
+void WriteMemoryTrimReply(const bool trimmed, std::string& msg);
+
+Status ReadMemoryTrimReply(const json& root, bool& trimmed);
+
 void WriteCreateStreamRequest(const ObjectID& object_id, std::string& msg);
 
 Status ReadCreateStreamRequest(const json& root, ObjectID& object_id);

src/common/util/uuid.h

@@ -168,8 +168,6 @@ inline ObjectID GenerateSignature() {
   return 0x7FFFFFFFFFFFFFFFUL & detail::cycleclock::now();
 }
 
-inline bool IsBlob(ObjectID id) { return id & 0x8000000000000000UL; }
-
 const std::string ObjectIDToString(const ObjectID id);
 
 const std::string ObjectIDToString(const PlasmaID id);
@@ -267,10 +265,27 @@ inline ID GenerateBlobID(const void* ptr) {
 }
 
 template <typename ID = ObjectID>
-ID EmptyBlobID() {
+inline ID EmptyBlobID() {
   return GenerateBlobID<ID>(0x8000000000000000UL);
 }
 
+template <typename ID = ObjectID>
+inline ID PlaceholderBlobID() {
+  return GenerateBlobID<ID>(std::numeric_limits<uintptr_t>::max());
+}
+
+inline bool IsBlob(ObjectID id) { return id & 0x8000000000000000UL; }
+
+template <typename ID = ObjectID>
+inline bool IsEmptyBlobID(ID id) {
+  return EmptyBlobID<ID>() == id;
+}
+
+template <typename ID = ObjectID>
+inline bool IsPlaceholderBlobID(ID id) {
+  return PlaceholderBlobID<ID>() == id;
+}
+
 template <typename ID>
 std::string IDToString(ID id);
 

src/server/async/socket_server.cc

@@ -297,6 +297,8 @@ bool SocketConnection::processMessage(const std::string& message_in) {
     return doLabelObject(root);
   } else if (cmd == command_t::CLEAR_REQUEST) {
     return doClear(root);
+  } else if (cmd == command_t::MEMORY_TRIM_REQUEST) {
+    return doMemoryTrim(root);
   } else if (cmd == command_t::CREATE_STREAM_REQUEST) {
     return doCreateStream(root);
   } else if (cmd == command_t::OPEN_STREAM_REQUEST) {
@@ -1078,6 +1080,17 @@ bool SocketConnection::doClear(const json& root) {
   return false;
 }
 
+bool SocketConnection::doMemoryTrim(const json& root) {
+  auto self(shared_from_this());
+  std::string message_out;
+
+  TRY_READ_REQUEST(ReadMemoryTrimRequest, root);
+  bool trimmed = bulk_store_->MemoryTrim();
+  WriteMemoryTrimReply(trimmed, message_out);
+  self->doWrite(message_out);
+  return false;
+}
+
 bool SocketConnection::doCreateStream(const json& root) {
   auto self(shared_from_this());
   ObjectID stream_id;

src/server/async/socket_server.h

@@ -104,6 +104,7 @@ class SocketConnection : public std::enable_shared_from_this<SocketConnection> {
   bool doIfPersist(json const& root);
   bool doLabelObject(json const& root);
   bool doClear(json const& root);
+  bool doMemoryTrim(json const& root);
 
   bool doCreateStream(json const& root);
   bool doOpenStream(json const& root);

src/server/memory/allocator.cc

@@ -39,6 +39,7 @@
 
 #include "server/memory/allocator.h"
 
+#include "common/util/logging.h"
 #include "server/memory/dlmalloc.h"
 #include "server/memory/mimalloc.h"
 

src/server/memory/malloc.cc

@@ -236,10 +236,11 @@ void* mmap_buffer(int64_t size, bool* is_committed, bool* is_zero) {
   size += kMmapRegionsGap;
 
   int fd = create_buffer(size);
-  return mmap_buffer(fd, size, is_committed, is_zero);
+  return mmap_buffer(fd, size, true, is_committed, is_zero);
 }
 
-void* mmap_buffer(int fd, int64_t size, bool* is_committed, bool* is_zero) {
+void* mmap_buffer(int fd, int64_t size, bool gap, bool* is_committed,
+                  bool* is_zero) {
   if (fd < 0) {
     LOG(ERROR) << "failed to create buffer during mmap: " << strerror(errno);
     return nullptr;
@@ -268,9 +269,12 @@ void* mmap_buffer(int fd, int64_t size, bool* is_committed, bool* is_zero) {
   MmapRecord& record = mmap_records[pointer];
   record.fd = fd;
   record.size = size;
+  record.kind = MmapRecord::Kind::kMalloc;
 
-  // We lie to dlmalloc/mimalloc about where mapped memory actually lives.
-  pointer = pointer_advance(pointer, kMmapRegionsGap);
+  if (gap) {
+    // We lie to dlmalloc/mimalloc about where mapped memory actually lives.
+    pointer = pointer_advance(pointer, kMmapRegionsGap);
+  }
   return pointer;
 }
 

src/server/memory/malloc.h

@@ -48,6 +48,12 @@ void GetMallocMapinfo(void* addr, int* fd, int64_t* map_length,
 struct MmapRecord {
   int fd = -1;
   int64_t size = -1;
+  enum class Kind {
+    kMalloc = 0,
+    kAllocator = 1,
+    kDiskMMap = 2,
+  };
+  Kind kind = Kind::kMalloc;
 };
 
 /// Hashtable that contains one entry per segment that we got from the OS
@@ -68,7 +74,8 @@ int create_buffer(int64_t size, std::string const& path);
 void* mmap_buffer(int64_t size, bool* is_committed, bool* is_zero);
 
 // Create a buffer, and mmap the buffer as the shared memory space.
-void* mmap_buffer(int fd, int64_t size, bool* is_committed, bool* is_zero);
+void* mmap_buffer(int fd, int64_t size, bool gap, bool* is_committed,
+                  bool* is_zero);
 
 // Unmap the buffer.
 int munmap_buffer(void* addr, int64_t size);