diff --git a/crate/memory/Cargo.toml b/crate/memory/Cargo.toml
index fb4fe38..309f0a8 100644
--- a/crate/memory/Cargo.toml
+++ b/crate/memory/Cargo.toml
@@ -2,6 +2,7 @@
 name = "ucore-memory"
 version = "0.1.0"
 authors = ["WangRunji <wangrunji0408@163.com>"]
+edition = "2018"
 
 [dependencies]
 log = "0.4"
\ No newline at end of file
diff --git a/crate/memory/src/addr.rs b/crate/memory/src/addr.rs
index f38ec26..c5ea30d 100644
--- a/crate/memory/src/addr.rs
+++ b/crate/memory/src/addr.rs
@@ -1,9 +1,8 @@
 use core::ops::{Add, AddAssign};
-use super::paging::*;
-use super::memory_set::*;
 
 pub type VirtAddr = usize;
 pub type PhysAddr = usize;
+
 pub const PAGE_SIZE: usize = 1 << 12;
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
@@ -80,13 +79,16 @@ impl Iterator for PageRange {
 /// frame for the swapmanager
 #[derive(Debug, Copy, Clone, PartialOrd, Ord)]
 #[repr(C)]
-pub struct Frame  {
-    page_table: usize, // the raw pointer for the frame's memory set's inactive page table
-    virtaddr: VirtAddr, // the virtual addr for the frame
-    token: usize, // the token for frame
+pub struct Frame {
+    /// the raw pointer for the frame's memory set's inactive page table
+    page_table: usize,
+    /// the virtual addr for the frame
+    virtaddr: VirtAddr,
+    /// the token for frame
+    token: usize,
 }
 
-impl Frame{
+impl Frame {
     pub fn get_page_table(&self) -> usize {
         self.page_table
     }
@@ -95,25 +97,23 @@ impl Frame{
         self.virtaddr
     }
 
-    pub fn get_token(&self) -> usize{
+    pub fn get_token(&self) -> usize {
         self.token
     }
 
-    pub fn new(pt: usize, addr: VirtAddr, pttoken: usize) -> Self{
+    pub fn new(pt: usize, addr: VirtAddr, pttoken: usize) -> Self {
         Frame {
             page_table: pt,
             virtaddr: addr,
             token: pttoken,
         }
     }
-} 
+}
 
-impl PartialEq for Frame{
+impl PartialEq for Frame {
     fn eq(&self, other: &Frame) -> bool {
         self.token == other.token && self.virtaddr == other.virtaddr
     }
 }
 
-impl Eq for Frame{
-    
-}
\ No newline at end of file
+impl Eq for Frame {}
\ No newline at end of file
diff --git a/crate/memory/src/cow.rs b/crate/memory/src/cow.rs
index aae8d5c..e616e42 100644
--- a/crate/memory/src/cow.rs
+++ b/crate/memory/src/cow.rs
@@ -206,7 +206,6 @@ impl FrameRcMap {
 
 pub mod test {
     use super::*;
-    use alloc::boxed::Box;
 
     #[test]
     fn test() {
diff --git a/crate/memory/src/lib.rs b/crate/memory/src/lib.rs
index 225d613..649d29d 100644
--- a/crate/memory/src/lib.rs
+++ b/crate/memory/src/lib.rs
@@ -1,15 +1,11 @@
-#![no_std]
+#![cfg_attr(not(test), no_std)]
 #![feature(alloc)]
 #![feature(nll)]
+#![feature(extern_crate_item_prelude)]
 
+// import macros from log
+use log::*;
 extern crate alloc;
-#[macro_use]
-extern crate log;
-
-// To use `println!` in test
-#[cfg(test)]
-#[macro_use]
-extern crate std;
 
 pub mod paging;
 pub mod cow;
@@ -17,4 +13,4 @@ pub mod swap;
 pub mod memory_set;
 mod addr;
 
-pub use addr::*;
\ No newline at end of file
+pub use crate::addr::*;
\ No newline at end of file
diff --git a/crate/memory/src/memory_set.rs b/crate/memory/src/memory_set.rs
index 1853f3b..92f2dfc 100644
--- a/crate/memory/src/memory_set.rs
+++ b/crate/memory/src/memory_set.rs
@@ -4,7 +4,7 @@
 use alloc::vec::Vec;
 use core::fmt::{Debug, Error, Formatter};
 use super::*;
-use paging::*;
+use crate::paging::*;
 
 /// an inactive page table
 /// Note: InactivePageTable is not a PageTable
diff --git a/crate/memory/src/swap/enhanced_clock.rs b/crate/memory/src/swap/enhanced_clock.rs
index 5d5d0bf..2651ba7 100644
--- a/crate/memory/src/swap/enhanced_clock.rs
+++ b/crate/memory/src/swap/enhanced_clock.rs
@@ -2,7 +2,7 @@
 
 use alloc::collections::VecDeque;
 use super::*;
-use paging::Entry;
+use crate::paging::Entry;
 
 #[derive(Default)]
 pub struct EnhancedClockSwapManager {
diff --git a/crate/memory/src/swap/mod.rs b/crate/memory/src/swap/mod.rs
index ede0199..21a8259 100644
--- a/crate/memory/src/swap/mod.rs
+++ b/crate/memory/src/swap/mod.rs
@@ -10,7 +10,6 @@ use super::*;
 use super::paging::*;
 use super::memory_set::InactivePageTable;
 use super::addr::Frame;
-use alloc::rc::Rc;
 use core::ops::{Deref, DerefMut};
 
 //pub use self::fifo::FifoSwapManager;