diff --git a/src/libos/Enclave_config.xml b/src/libos/Enclave_config.xml
index f18079c4..054bf805 100644
--- a/src/libos/Enclave_config.xml
+++ b/src/libos/Enclave_config.xml
@@ -3,7 +3,7 @@
   <ProdID>0</ProdID>
   <ISVSVN>0</ISVSVN>
   <StackMaxSize>0x80000</StackMaxSize>
-  <HeapMaxSize>0x1000000</HeapMaxSize>
+  <HeapMaxSize>0x6000000</HeapMaxSize>
   <TCSNum>8</TCSNum>
   <TCSPolicy>1</TCSPolicy>
   <DisableDebug>0</DisableDebug>
diff --git a/src/libos/src/process.rs b/src/libos/src/process.rs
index 8a98039e..36d895a4 100644
--- a/src/libos/src/process.rs
+++ b/src/libos/src/process.rs
@@ -152,7 +152,7 @@ pub fn run_task() -> Result<(), &'static str> {
         let process : &Process = &guard;
         pid = process.pid;
         //println!("Run process: {:#x?}", process);
-        println!("Run process (pid = {})", process.pid);
+        //println!("Run process (pid = {})", process.pid);
         new_task = &process.task as *const Task
     };
 
@@ -221,7 +221,7 @@ impl Process {
 
         self.code_vma = Vma::from_program_header(&code_ph)?;
         self.data_vma = Vma::from_program_header(&data_ph)?;
-        self.stack_vma = Vma::new(8 * 1024, 4096,
+        self.stack_vma = Vma::new(32 * 1024 * 1024, 4096,
             vma::Perms(vma::PERM_R | vma::PERM_W))?;
 
         self.program_base_addr = self.alloc_mem_for_vmas(elf_file)?;
diff --git a/src/libos/src/vma.rs b/src/libos/src/vma.rs
index 684c0c86..74b87474 100644
--- a/src/libos/src/vma.rs
+++ b/src/libos/src/vma.rs
@@ -90,8 +90,8 @@ pub fn malloc_batch(vma_list: &mut [&mut Vma], mapped_data: &[u8])
     let mut max_align = VMA_MIN_MEM_ALIGN;
     let mut total_size = 0;
     for vma in vma_list.into_iter() {
-        let mem_begin = round_up(total_size, vma.mem_align);
-        let mem_end = mem_begin + round_up(vma.mem_size, vma.mem_align);
+        let mem_begin = align_up(total_size, vma.mem_align);
+        let mem_end = mem_begin + align_up(vma.mem_size, vma.mem_align);
 
         if vma.file_is_mapped {
             if vma.mem_addr < mem_begin ||
@@ -114,8 +114,8 @@ pub fn malloc_batch(vma_list: &mut [&mut Vma], mapped_data: &[u8])
     let program_base_addr = memobj.get_addr();
     let mut mem_cur = program_base_addr;
     for vma in vma_list.into_iter() {
-        vma.mem_begin = round_up(mem_cur, vma.mem_align);
-        vma.mem_end = vma.mem_begin + round_up(vma.mem_size, vma.mem_align);
+        vma.mem_begin = align_up(mem_cur, vma.mem_align);
+        vma.mem_end = vma.mem_begin + align_up(vma.mem_size, vma.mem_align);
         vma.mem_addr += program_base_addr;
         vma.underlying = memobj.clone();
 
@@ -137,13 +137,19 @@ pub fn mprotect_batch(vma_list: &[&Vma])
     -> Result<(), &'static str>
 {
     for vma in vma_list.into_iter() {
-        let start = vma.mem_begin as size_t;
-        let size = (vma.mem_end - vma.mem_begin) as size_t;
+        // If don't need to change memory permissions
+        if vma.mem_flags == Perms(PERM_R | PERM_W) {
+            continue;
+        }
+
+        let start = align_down(vma.mem_addr, 4096);
+        let size = align_up(vma.mem_size, 4096);
         let perms = vma.mem_flags.0 as uint64_t;
         let status = unsafe {
             //TODO: use proper permissions
             //TODO: reset the permissions when drop VMA
             //trts_mprotect(start, size, perms)
+            //println!("trts_mprotect: start = {}, size = {}", start, size);
             trts_mprotect(start, size, (PERM_R | PERM_W | PERM_X) as uint64_t)
         };
         if (status != sgx_status_t::SGX_SUCCESS) {
@@ -185,10 +191,14 @@ impl<'a> From<&'a program::Flags> for Perms {
     }
 }
 
-fn round_up(addr: usize, align: usize) -> usize {
+fn align_up(addr: usize, align: usize) -> usize {
     (addr + (align - 1)) / align * align
 }
 
+fn align_down(addr: usize, align: usize) -> usize {
+    addr & !(align - 1)
+}
+
 #[link(name = "sgx_trts")]
 extern {
     pub fn trts_mprotect(start: size_t, size: size_t, perms: uint64_t) -> sgx_status_t;
diff --git a/test/hello_world_raw/main.c b/test/hello_world_raw/main.c
index 127d511c..1ad27131 100644
--- a/test/hello_world_raw/main.c
+++ b/test/hello_world_raw/main.c
@@ -4,6 +4,6 @@ char str_buf[] = "Hello World!\n";
 unsigned long str_size = sizeof(str_buf);
 
 void _start(void) {
-    __rusgx_write(1, str_buf, str_size);
+    //__rusgx_write(1, str_buf, str_size);
     __rusgx_exit(0);
 }
diff --git a/test/spawn_and_wait4_raw/main.c b/test/spawn_and_wait4_raw/main.c
index 92ff5417..793730fa 100644
--- a/test/spawn_and_wait4_raw/main.c
+++ b/test/spawn_and_wait4_raw/main.c
@@ -7,7 +7,7 @@ static void print_ok(void) {
     __rusgx_write(1, success_str_buf, success_str_size);
 }
 
-#define NUM_CHILDREN            100
+#define NUM_CHILDREN            10
 
 void _start(void) {
     for (int ci = 0; ci < NUM_CHILDREN; ci++) {
@@ -16,7 +16,6 @@ void _start(void) {
 
         ret = __rusgx_spawn(&pid, "hello_world_raw/bin.encrypted", NULL, NULL);
         if (ret < 0) { __rusgx_exit(0); }
-        print_ok();
 
         int status;
         ret = __rusgx_wait4(pid, &status, 0);