diff --git a/dnn/src/common/utils.cpp b/dnn/src/common/utils.cpp
index a11f340a..2dd2ca70 100644
--- a/dnn/src/common/utils.cpp
+++ b/dnn/src/common/utils.cpp
@@ -156,42 +156,15 @@ void megdnn::infer_conv_shape2d(size_t ih, size_t iw, size_t fh, size_t fw,
 WorkspaceBundle::WorkspaceBundle(void* ptr, SmallVector<size_t> sizes_in_bytes,
                                  size_t align_in_bytes)
         : m_ptr(ptr),
+          m_sizes(std::move(sizes_in_bytes)),
           m_align_in_bytes(align_in_bytes) {
     m_aligned_sizes.reserve(m_sizes.size());
-    m_sizes.push_back(sizes_in_bytes);
-    size_t reduce_size = 0_z;
-    m_reduce_num.push_back(0_z);
-    for (auto size : m_sizes[0]) {
+    for (auto size : m_sizes) {
         auto aligned_size = size;
         if (size % m_align_in_bytes != 0) {
             aligned_size += m_align_in_bytes - size % m_align_in_bytes;
         }
         m_aligned_sizes.push_back(aligned_size);
-        m_reduce_sizes.push_back(reduce_size);
-        reduce_size += aligned_size;
-    }
-}
-
-WorkspaceBundle::WorkspaceBundle(
-        SmallVector<SmallVector<size_t>> vector_sizes_in_bytes, void* ptr,
-        size_t align_in_bytes)
-        : m_ptr(ptr),
-          m_sizes(vector_sizes_in_bytes),
-          m_align_in_bytes(align_in_bytes) {
-    size_t nr_workspace = 0_z;
-    size_t reduce_size = 0_z;
-    for (auto sizes_in_bytes: vector_sizes_in_bytes) {
-        m_reduce_num.push_back(nr_workspace);
-        for (auto size : sizes_in_bytes) {
-            auto aligned_size = size;
-            if (size % m_align_in_bytes != 0) {
-                aligned_size += m_align_in_bytes - size % m_align_in_bytes;
-            }
-            m_aligned_sizes.push_back(aligned_size);
-            m_reduce_sizes.push_back(reduce_size);
-            reduce_size += aligned_size;
-            nr_workspace++;
-        }
     }
 }
 
@@ -199,39 +172,22 @@ void* WorkspaceBundle::ptr() const {
     return m_ptr;
 }
 
-void* WorkspaceBundle::get(size_t dim1, size_t dim0) const {
-    megdnn_assert(dim1 < m_sizes.size(), "dim1 is out of range");
-    megdnn_assert(dim0 < m_sizes[dim1].size(), "dim0 is out of range");
+void* WorkspaceBundle::get(size_t i) const {
     auto addr = reinterpret_cast<uintptr_t>(m_ptr);
     if (addr % m_align_in_bytes != 0)
         addr += m_align_in_bytes - addr % m_align_in_bytes;
-    size_t index = m_reduce_num[dim1] + dim0;
-    addr += m_reduce_sizes[index];
-    return reinterpret_cast<void*>(addr);
-}
-
-void* WorkspaceBundle::get(size_t dim0) const {
-    megdnn_assert(dim0 < m_aligned_sizes.size(), "dim0 is out of range");
-    auto addr = reinterpret_cast<uintptr_t>(m_ptr);
-    if (addr % m_align_in_bytes != 0)
-        addr += m_align_in_bytes - addr % m_align_in_bytes;
-    addr += m_reduce_sizes[dim0];
+    for (size_t j = 0; j < i; ++j) {
+        addr += m_aligned_sizes[j];
+    }
     return reinterpret_cast<void*>(addr);
 }
 
 size_t WorkspaceBundle::nr_workspace() const {
-    return m_aligned_sizes.size();
-}
-
-size_t WorkspaceBundle::get_size(size_t dim1, size_t dim0) const {
-    megdnn_assert(dim1 < m_sizes.size(), "dim1 is out of range");
-    megdnn_assert(dim0 < m_sizes[dim1].size(), "dim0 is out of range");
-    return m_sizes[dim1][dim0];
+    return m_sizes.size();
 }
 
-size_t WorkspaceBundle::get_size(size_t dim0) const {
-    megdnn_assert(dim0 < m_aligned_sizes.size(), "dim0 is out of range");
-    return m_sizes[0][dim0];
+size_t WorkspaceBundle::get_size(size_t i) const {
+    return m_sizes[i];
 }
 
 void WorkspaceBundle::set(void* ptr) {
diff --git a/dnn/src/common/utils.h b/dnn/src/common/utils.h
index d73a01e7..449c9b04 100644
--- a/dnn/src/common/utils.h
+++ b/dnn/src/common/utils.h
@@ -194,15 +194,8 @@ std::unique_ptr<T> make_unique(Args&&... args) {
  */
 class WorkspaceBundle {
 public:
-    WorkspaceBundle(void* ptr = nullptr,
-                    SmallVector<size_t> sizes_in_bytes = {},
+    WorkspaceBundle(void* ptr, SmallVector<size_t> sizes_in_bytes,
                     size_t align_in_bytes = 512);
-
-    /**
-     * construct 2D workspace buldle
-     */
-    WorkspaceBundle(SmallVector<SmallVector<size_t>> vector_sizes_in_bytes,
-                    void* ptr, size_t align_in_bytes = 512);
     /**
      * \returns raw workspace ptr.
      *
@@ -211,45 +204,26 @@ public:
      */
     void* ptr() const;
     /**
-     * \returns the 2D [dim1, dim0] workspace ptr (aligned)
+     * \returns the i-th workspace ptr (aligned)
      */
-    void* get(size_t dim1, size_t dim0) const;
-    /**
-     * \returns the 1D [dim0] workspace ptr (aligned)
-     */
-    void* get(size_t dim0) const;
+    void* get(size_t i) const;
     /**
      * \returns total size taking into account paddings to solve alignment
      * issue.
      */
     size_t total_size_in_bytes() const;
-    /**
-     * \return the 2D [dim1, dim0] workspace size
-     */
-    size_t get_size(size_t dim1, size_t dim0) const;
-
-    /**
-     * \return the 1D [dim0] workspace size
-     */
-    size_t get_size(size_t dim0) const;
+    size_t get_size(size_t i) const;
     size_t nr_workspace() const;
     void set(void* ptr);
 
-    Workspace get_workspace(size_t dim1, size_t dim0) const {
-        return {static_cast<dt_byte*>(get(dim1, dim0)), get_size(dim1, dim0)};
-    }
-    Workspace get_workspace(size_t dim0) const {
-        return {static_cast<dt_byte*>(get(dim0)), get_size(dim0)};
+    Workspace get_workspace(size_t i) const {
+        return {static_cast<dt_byte*>(get(i)), get_size(i)};
     }
 
 private:
     void* m_ptr;
-    SmallVector<SmallVector<size_t>> m_sizes;
+    SmallVector<size_t> m_sizes;
     SmallVector<size_t> m_aligned_sizes;
-    //! all workspace size prefix sum
-    SmallVector<size_t> m_reduce_sizes;
-    //! dim1 workspace number prefix sum
-    SmallVector<size_t> m_reduce_num;
     size_t m_align_in_bytes;
 };
 
diff --git a/dnn/test/common/test_basic_types.cpp b/dnn/test/common/test_basic_types.cpp
index 899dc7d2..31a6c2e2 100644
--- a/dnn/test/common/test_basic_types.cpp
+++ b/dnn/test/common/test_basic_types.cpp
@@ -11,7 +11,6 @@
 
 #include "megdnn/basic_types.h"
 #include "megdnn/tensor_format.h"
-#include "src/common/utils.h"
 
 // clang-format off
 #include "test/common/utils.h"
@@ -279,21 +278,4 @@ TEST(BASIC_TYPES, TENSOR_LAYOUT_FMT_COLLAPSE_W) {
     }
 }
 
-TEST(MISC, WORKSPACE_BUNDLE) {
-    WorkspaceBundle bundle{
-            {{100, 200}, {435, 234, 143}, {422, 1325, 728}}, nullptr, 64};
-    bundle.set(reinterpret_cast<void*>(82l));
-    ASSERT_EQ(bundle.get(0), reinterpret_cast<void*>(128l));
-    void* dst = reinterpret_cast<void*>(128 + round_up(100, 64));
-    ASSERT_EQ(bundle.get(0, 1), dst);
-    dst = reinterpret_cast<void*>(128 + round_up(100, 64) + round_up(200, 64) +
-                                  round_up(435, 64));
-    ASSERT_EQ(bundle.get(1, 1), dst);
-    dst = reinterpret_cast<void*>(128l + round_up(100, 64) + round_up(200, 64) +
-                                  round_up(435, 64) + round_up(234, 64) +
-                                  round_up(143, 64) + round_up(422, 64) +
-                                  round_up(1325, 64));
-    ASSERT_EQ(bundle.get(2, 2), dst);
-}
-
 // vim: syntax=cpp.doxygen