diff --git a/sdk/base/plat_types.h b/sdk/base/plat_types.h
index 664b7fe..b475182 100644
--- a/sdk/base/plat_types.h
+++ b/sdk/base/plat_types.h
@@ -7,8 +7,8 @@
 #endif
 
 #define SIZE_KB(n)                  ((n) * 1024)
-#define SIZE_MB(n)                  SIZE_KB(n * 1024)
-#define SIZE_GB(n)                  SIZE_MB(n * 1024)
+#define SIZE_MB(n)                  SIZE_KB((n) * 1024)
+#define SIZE_GB(n)                  SIZE_MB((n) * 1024)
 
 #define SEC_2_MS(s)                 ((s) * 1000)
 #define MSEC_2_US(ms)               ((ms) * 1000)
diff --git a/usb/usb_io.cpp b/usb/usb_io.cpp
index 7a034d6..4f2ee37 100644
--- a/usb/usb_io.cpp
+++ b/usb/usb_io.cpp
@@ -98,12 +98,12 @@ async_usb_gadget::async_usb_gadget(std::function<FUNCTION_PROTO_COMMAND_HANDLE>
 	threads_.set_exception_handler(excep);
 	unit_in_ = unit_out_ = global_info::page_size;	// dev_->get_max_packet();
 
-	// allocate 10MB for IO
+	// allocate 1MB for IO
 #ifdef MEM_POOL
-	io_buf_ = new dyn_mem_pool(256, unit_out_);
+	io_buf_ = new dyn_mem_pool(SIZE_MB(1) / unit_out_, unit_out_);
 	utils::to_log(LOG_LEVEL_DEBUG, "Prepare %u(%u * %u) for IO.\n", io_buf_->count() * unit_out_, io_buf_->count(), unit_in_);
 #else
-	for(int i = 0; i < SIZE_MB(10) / unit_out_; ++i)
+	for(int i = 0; i < SIZE_MB(1) / unit_out_; ++i)
 	{
 		dyn_mem_ptr buf = dyn_mem::memory(unit_out_);
 		if(buf)