diff --git a/src/memory/alloc.h b/src/memory/alloc.h
index 6fe2c41..875bbc9 100644
--- a/src/memory/alloc.h
+++ b/src/memory/alloc.h
@@ -106,41 +106,14 @@ public:
 
 namespace detail {
 
-template <typename T>
-class non_atomic {
-    T val_;
-
-public:
-    void store(T val, std::memory_order) noexcept {
-        val_ = val;
-    }
-
-    T load(std::memory_order) const noexcept {
-        return val_;
-    }
-
-    bool compare_exchange_weak(T&, T val, std::memory_order) noexcept {
-        // always return true
-        val_ = val;
-        return true;
-    }
-};
-
-class non_lock {
-public:
-    void lock  (void) noexcept {}
-    void unlock(void) noexcept {}
-};
-
-template <template <typename> class Atomic>
 class fixed_alloc_base {
 protected:
     std::size_t init_expand_;
-    Atomic<void*> cursor_;
+    void      * cursor_;
 
     void init(std::size_t init_expand) {
         init_expand_ = init_expand;
-        cursor_.store(nullptr, std::memory_order_relaxed);
+        cursor_ = nullptr;
     }
 
     static void** node_p(void* node) {
@@ -154,20 +127,13 @@ protected:
 public:
     void swap(fixed_alloc_base& rhs) {
         std::swap(this->init_expand_, rhs.init_expand_);
-        auto tmp = this->cursor_.load(std::memory_order_relaxed);
-        this->cursor_.store(rhs.cursor_.load(std::memory_order_relaxed), std::memory_order_relaxed);
-        rhs.cursor_.store(tmp, std::memory_order_relaxed);
+        std::swap(this->cursor_     , rhs.cursor_     );
     }
 
     void free(void* p) {
         if (p == nullptr) return;
-        while (1) {
-            next(p) = cursor_.load(std::memory_order_acquire);
-            if (cursor_.compare_exchange_weak(next(p), p, std::memory_order_release)) {
-                break;
-            }
-            std::this_thread::yield();
-        }
+        next(p) = cursor_;
+        cursor_ = p;
     }
 
     void free(void* p, std::size_t) {
@@ -177,12 +143,10 @@ public:
 
 } // namespace detail
 
-template <std::size_t BlockSize, typename AllocP = scope_alloc<>,
-          template <typename> class Atomic = detail::non_atomic,
-          typename Lock = detail::non_lock>
-class fixed_alloc : public detail::fixed_alloc_base<Atomic> {
+template <std::size_t BlockSize, typename AllocP = scope_alloc<>>
+class fixed_alloc : public detail::fixed_alloc_base {
 public:
-    using base_t = detail::fixed_alloc_base<Atomic>;
+    using base_t = detail::fixed_alloc_base;
     using alloc_policy = AllocP;
 
     enum : std::size_t {
@@ -195,22 +159,17 @@ public:
 
 private:
     alloc_policy alloc_;
-    Lock lc_;
 
-    void* expand() {
-        IPC_UNUSED_ auto guard = ipc::detail::unique_lock(lc_);
-        auto c = this->cursor_.load(std::memory_order_relaxed);
-        if (c != nullptr) {
-            return c;
+    void* try_expand() {
+        if (this->cursor_ != nullptr) {
+            return this->cursor_;
         }
-        auto a = alloc_.alloc(block_size);
-        this->cursor_.store(a, std::memory_order_relaxed);
-        auto p = this->node_p(a);
+        auto p = this->node_p(this->cursor_ = alloc_.alloc(block_size));
         auto size = alloc_.size_of(p);
         if (size > 0) for (std::size_t i = 0; i < (size / block_size) - 1; ++i)
             p = this->node_p((*p) = reinterpret_cast<byte_t*>(p) + block_size);
         (*p) = nullptr;
-        return a;
+        return this->cursor_;
     }
 
 public:
@@ -223,13 +182,11 @@ public:
 
 public:
     void swap(fixed_alloc& rhs) {
-        IPC_UNUSED_ auto guard = ipc::detail::unique_lock(lc_);
         std::swap(this->alloc_, rhs.alloc_);
         base_t::swap(rhs);
     }
 
     void clear() {
-        IPC_UNUSED_ auto guard = ipc::detail::unique_lock(lc_);
         alloc_.clear();
         this->init(this->init_expand_);
     }
@@ -239,14 +196,8 @@ public:
     }
 
     void* alloc() {
-        void* p;
-        while (1) {
-            p = expand();
-            if (this->cursor_.compare_exchange_weak(p, this->next(p), std::memory_order_release)) {
-                break;
-            }
-            std::this_thread::yield();
-        }
+        void* p = try_expand();
+        this->cursor_ = this->next(p);
         return p;
     }
 
@@ -264,8 +215,5 @@ using page_alloc = fixed_alloc<4096>;
 template <std::size_t BlockSize>
 using page_fixed_alloc = fixed_alloc<BlockSize, page_alloc>;
 
-template <std::size_t BlockSize>
-using locked_fixed_alloc = fixed_alloc<BlockSize, page_alloc, std::atomic, ipc::spin_lock>;
-
 } // namespace mem
 } // namespace ipc
diff --git a/src/memory/wrapper.h b/src/memory/wrapper.h
index 71c7996..4df0de9 100644
--- a/src/memory/wrapper.h
+++ b/src/memory/wrapper.h
@@ -125,12 +125,12 @@ constexpr bool operator!=(const allocator_wrapper<T, AllocP>&, const allocator_w
 ////////////////////////////////////////////////////////////////
 
 template <std::size_t BlockSize>
-using locked_fixed = ipc::mem::detail::fixed<BlockSize, locked_fixed_alloc>;
+using page_fixed = ipc::mem::detail::fixed<BlockSize, page_fixed_alloc>;
 
-using locked_pool_alloc = detail::pool_alloc<locked_fixed>;
+using page_pool_alloc = detail::pool_alloc<page_fixed>;
 
 template <typename T>
-using locked_allocator = allocator_wrapper<T, locked_pool_alloc>;
+using page_allocator = allocator_wrapper<T, page_pool_alloc>;
 
 template <typename AllocP>
 class synchronized {
@@ -140,7 +140,7 @@ public:
 private:
     spin_lock lc_;
     std::multimap<std::size_t, alloc_policy*, std::less<std::size_t>,
-                  locked_allocator<std::pair<const std::size_t, alloc_policy*>>> allocs_;
+                  page_allocator<std::pair<const std::size_t, alloc_policy*>>> allocs_;
 
     struct alloc_t {
         synchronized* t_;
@@ -156,11 +156,11 @@ private:
                     std::tie(s_, a_) = *it;
                     t_->allocs_.erase(it);
                 }
+                if (a_ == nullptr) {
+                    a_ = static_cast<alloc_policy*>(page_pool_alloc::alloc(sizeof(alloc_policy)));
+                }
             }
-            if (a_ == nullptr) {
-                a_ = static_cast<alloc_policy*>(locked_pool_alloc::alloc(sizeof(alloc_policy)));
-                ::new (a_) alloc_policy;
-            }
+            ::new (a_) alloc_policy;
         }
 
         ~alloc_t() {
@@ -189,22 +189,15 @@ private:
 
 public:
     ~synchronized() {
-        for (auto& pair : allocs_) {
-            pair.second->~AllocP();
-            locked_pool_alloc::free(pair.second, sizeof(alloc_policy));
-        }
+        clear();
     }
 
     void clear() {
-        auto guard = ipc::detail::unique_lock(lc_);
-        std::vector<alloc_policy*> vec(allocs_.size());
-        std::size_t i = 0;
+        IPC_UNUSED_ auto guard = ipc::detail::unique_lock(lc_);
         for (auto& pair : allocs_) {
-            vec[i++] = pair.second;
+            pair.second->~AllocP();
+            page_pool_alloc::free(pair.second, sizeof(alloc_policy));
         }
-        allocs_.clear();
-        guard.unlock();
-        for (auto alc : vec) delete alc;
     }
 
     void* alloc(std::size_t size) {