Add implementation of readinto to decrease amount of copy operations

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ### New features
 * Update S3ClientConfig to pass in the configuration for allowing unsigned requests, under boolean flag `unsigned`.
+* Improve the performance of `s3reader` when utilized with `pytorch.load` by incorporating support for the `readinto` method.
 
 
 ## v1.2.2 (March 22, 2024)

s3torchconnector/src/s3torchconnector/s3reader.py

@@ -53,6 +53,34 @@ def prefetch(self) -> None:
         if self._stream is None:
             self._stream = self._get_stream()
 
+    def readinto(self, buf) -> int:
+        """Read up to len(buf) bytes into a pre-allocated, writable bytes-like object buf.
+        Return the number of bytes read. If no bytes available, zero is returned.
+
+        Args:
+            buf : writable bytes-like object
+
+        Returns:
+            int : numer of bytes read or zero, if no bytes available
+        """
+        buf_size = len(buf)
+        if self._position_at_end() or buf_size == 0:
+            # If no bytes are available or no place to write data, zero should be returned
+            return 0
+
+        self.prefetch()
+        assert self._stream is not None
+
+        cur_pos = self._position
+        # preload enough bytes in buffer
+        self.seek(buf_size, SEEK_CUR)
+        # restore position, before starting to write into buf
+        self._buffer.seek(cur_pos)
+        size = self._buffer.readinto(buf)
+        self._position = self._buffer.tell()
+
+        return size
+
     def read(self, size: Optional[int] = None) -> bytes:
         """Read up to size bytes from the object and return them.
 
@@ -82,7 +110,9 @@ def read(self, size: Optional[int] = None) -> bytes:
         if size is None or size < 0:
             # Special case read() all to use O(n) algorithm
             self._buffer.seek(0, SEEK_END)
-            self._buffer.write(b"".join(self._stream))
+            for batch in self._stream:
+                self._buffer.write(batch)
+
             # Once we've emptied the buffer, we'll always be at EOF!
             self._size = self._buffer.tell()
         else:

s3torchconnector/tst/e2e/test_e2e_s3checkpoint.py

@@ -2,13 +2,18 @@
 #  // SPDX-License-Identifier: BSD
 
 import torch
+import pytest
 
 from s3torchconnector import S3Checkpoint
 from models.net import Net
 
 
-def test_general_checkpointing(checkpoint_directory):
-    tensor = torch.tensor([[0.1, 1.2], [2.2, 3.1], [4.9, 5.2]])
+@pytest.mark.parametrize(
+    "tensor_dimensions",
+    [[3, 2], [10, 1024, 1024]],
+)
+def test_general_checkpointing(checkpoint_directory, tensor_dimensions):
+    tensor = torch.rand(tensor_dimensions)
     checkpoint_name = "general_checkpoint.pt"
     checkpoint = S3Checkpoint(region=checkpoint_directory.region)
     s3_uri = f"{checkpoint_directory.s3_uri}/{checkpoint_name}"

s3torchconnector/tst/unit/test_s3reader.py

@@ -21,7 +21,6 @@
 
 log = logging.getLogger(__name__)
 
-
 TEST_BUCKET = "test-bucket"
 TEST_KEY = "test-key"
 MOCK_OBJECT_INFO = Mock(ObjectInfo)
@@ -182,14 +181,17 @@ def test_over_read(stream: List[bytes], overread: int):
 def test_seeks_end():
     s3reader = S3Reader(TEST_BUCKET, TEST_KEY, lambda: None, lambda: iter([]))
     s3reader._size = 10
+    buf = memoryview(bytearray(10))
 
     assert s3reader.seek(0, SEEK_END) == 10
     assert s3reader.tell() == 10
     assert s3reader.read() == b""
+    assert s3reader.readinto(buf) == 0
 
     assert s3reader.seek(0, SEEK_CUR) == 10
     assert s3reader.tell() == 10
     assert s3reader.read() == b""
+    assert s3reader.readinto(buf) == 0
 
 
 def test_not_writable():
@@ -301,3 +303,110 @@ def test_s3reader_writes_size_after_read_all_explicit(stream: List[bytes]):
     assert s3reader.read(1) == b""
     # Once we've read past the end, we know how big the file is
     assert s3reader._size == total_length
+
+
+@given(
+    lists(binary(min_size=2, max_size=3), min_size=0, max_size=3),
+    integers(min_value=0, max_value=1),
+)
+def test_s3reader_readinto_buffer_smaller_then_chunks(
+    stream: List[bytes], buf_size: int
+):
+    s3reader = S3Reader(TEST_BUCKET, TEST_KEY, lambda: None, lambda: iter(stream))
+    assert s3reader._size is None
+    total_length = sum(map(len, stream))
+    buf = memoryview(bytearray(buf_size))
+    # We're able to read all the available data or the data that can be accommodated in buf
+    if buf_size > 0 and total_length > 0:
+        assert s3reader.readinto(buf) == buf_size
+        assert s3reader.tell() == buf_size
+        # We haven't reached the end yet
+        assert s3reader._size is None
+        # confirm that read data is the same as in source
+        assert buf[:buf_size] == (b"".join(stream))[:buf_size]
+    else:
+        assert s3reader.readinto(buf) == 0
+        assert s3reader.tell() == 0
+
+
+@given(
+    lists(binary(min_size=2, max_size=3), min_size=1, max_size=3),
+    integers(min_value=3, max_value=10),
+)
+def test_s3reader_readinto_buffer_bigger_then_chunks(
+    stream: List[bytes], buf_size: int
+):
+    s3reader = S3Reader(TEST_BUCKET, TEST_KEY, lambda: None, lambda: iter(stream))
+    assert s3reader._size is None
+    total_length = sum(map(len, stream))
+    buf = memoryview(bytearray(buf_size))
+    should_read_bytes_in_first_pass = min(buf_size, total_length)
+    # We're able to read all the available data or the data that can be accommodated in buf
+    assert s3reader.readinto(buf) == should_read_bytes_in_first_pass
+    assert s3reader.tell() == should_read_bytes_in_first_pass
+    all_data = b"".join(stream)
+    # confirm that read data is the same as in source
+    assert (
+        buf[:should_read_bytes_in_first_pass]
+        == all_data[:should_read_bytes_in_first_pass]
+    )
+    if total_length < buf_size:
+        assert s3reader._size == total_length
+
+    should_read_bytes_in_second_pass = max(
+        min(buf_size, total_length - should_read_bytes_in_first_pass), 0
+    )
+    if should_read_bytes_in_second_pass > 0:
+        # We're able to read all the available data or the data that can be accommodated in buf
+        assert s3reader.readinto(buf) == should_read_bytes_in_second_pass
+        total_read = should_read_bytes_in_first_pass + should_read_bytes_in_second_pass
+        assert s3reader.tell() == total_read
+        # confirm that read data is the same as in source
+        assert (
+            buf[:should_read_bytes_in_second_pass]
+            == all_data[should_read_bytes_in_first_pass:total_read]
+        )
+        if total_length < total_read:
+            assert s3reader._size == total_read
+
+
+@given(
+    lists(binary(min_size=2, max_size=12), min_size=1, max_size=5),
+    integers(min_value=3, max_value=10),
+    integers(min_value=0, max_value=1),
+)
+def test_s3reader_mixing_readinto_and_read(
+    stream: List[bytes], buf_size: int, flip: int
+):
+    position = 0
+    loops_count = 20
+    all_data = b"".join(stream)
+    total_length = len(all_data)
+    buf = memoryview(bytearray(buf_size))
+    s3reader = S3Reader(TEST_BUCKET, TEST_KEY, lambda: None, lambda: iter(stream))
+    for i in range(0, loops_count):
+        if position >= total_length:
+            break
+
+        if (i + flip) % 2 == 0:
+            result = s3reader.read(buf_size)
+            # confirm that read data is the same as in source
+            if position + buf_size < total_length:
+                assert result[:buf_size] == all_data[position : position + buf_size]
+            else:
+                read_bytes = total_length - position
+                assert result[:read_bytes] == all_data[position:total_length]
+            position += buf_size
+        else:
+            read_bytes = s3reader.readinto(buf)
+            # confirm that read data is the same as in source
+            assert buf[position:read_bytes] == all_data[position:read_bytes]
+            position += read_bytes
+
+        if position > total_length:
+            # we read all the data, it is time to stop
+            assert s3reader.tell() == total_length
+            break
+        else:
+            # confirm that position is as expected
+            assert s3reader.tell() == position