Remove padding from device_memory_resource (#1278)

This PR removes the `align_up` call that enforces 8B padding on all RMM device memory allocations. Padding, where needed, should be the responsibility of callers, possibly with the help of a padding adapter. It should not be enforced by rmm.

I looked at all other calls to `align_up` in the library but didn't find any others that needed removing. The other calls all seemed to be used to guarantee specific intentional alignment requirements of other memory resources or adapters. I would appreciate verification from reviewers, though.

I've labeled this PR as breaking because it could break consumers that were implicitly relying on the current padding behavior.

Resolves #865
Resolves #1156

Authors:
  - Vyas Ramasubramani (https://github.com/vyasr)

Approvers:
  - Rong Ou (https://github.com/rongou)
  - Mark Harris (https://github.com/harrism)

URL: #1278

include/rmm/mr/device/device_memory_resource.hpp

@@ -105,7 +105,7 @@ class device_memory_resource {
    */
   void* allocate(std::size_t bytes, cuda_stream_view stream = cuda_stream_view{})
   {
-    return do_allocate(rmm::detail::align_up(bytes, allocation_size_alignment), stream);
+    return do_allocate(bytes, stream);
   }
 
   /**
@@ -128,7 +128,7 @@ class device_memory_resource {
    */
   void deallocate(void* ptr, std::size_t bytes, cuda_stream_view stream = cuda_stream_view{})
   {
-    do_deallocate(ptr, rmm::detail::align_up(bytes, allocation_size_alignment), stream);
+    do_deallocate(ptr, bytes, stream);
   }
 
   /**
@@ -178,9 +178,6 @@ class device_memory_resource {
   }
 
  private:
-  // All allocations are padded to a multiple of allocation_size_alignment bytes.
-  static constexpr auto allocation_size_alignment = std::size_t{8};
-
   /**
    * @brief Allocates memory of size at least \p bytes.
    *

tests/logger_tests.cpp

@@ -113,7 +113,7 @@ void expect_log_events(std::string const& filename,
                // EXPECT_EQ(expected.stream, actual.stream);
                EXPECT_EQ(expected.act, actual.act);
                // device_memory_resource automatically pads an allocation to a multiple of 8 bytes
-               EXPECT_EQ(rmm::detail::align_up(expected.size, 8), actual.size);
+               EXPECT_EQ(expected.size, actual.size);
                EXPECT_EQ(expected.pointer, actual.pointer);
                return true;
              });

tests/mr/device/aligned_mr_tests.cpp

@@ -87,9 +87,8 @@ TEST(AlignedTest, DefaultAllocationAlignmentPassthrough)
   cuda_stream_view stream;
   void* const pointer = int_to_address(123);
 
-  // device_memory_resource aligns to 8.
   {
-    auto const size{8};
+    auto const size{5};
     EXPECT_CALL(mock, do_allocate(size, stream)).WillOnce(Return(pointer));
     EXPECT_CALL(mock, do_deallocate(pointer, size, stream)).Times(1);
   }
@@ -110,9 +109,8 @@ TEST(AlignedTest, BelowAlignmentThresholdPassthrough)
 
   cuda_stream_view stream;
   void* const pointer = int_to_address(123);
-  // device_memory_resource aligns to 8.
   {
-    auto const size{8};
+    auto const size{3};
     EXPECT_CALL(mock, do_allocate(size, stream)).WillOnce(Return(pointer));
     EXPECT_CALL(mock, do_deallocate(pointer, size, stream)).Times(1);
   }