//#import <mach/mach.h>
long getResidentMemory
{
    struct task_basic_info t_info;
    mach_msg_type_number_t t_info_count = TASK_BASIC_INFO_COUNT;
    
    int r = task_info(mach_task_self(), TASK_BASIC_INFO, (task_info_t)&t_info, &t_info_count);
    if (r == KERN_SUCCESS)
    {
        return t_info.resident_size;
    }
    else
    {
        return -1;
    }
}

package com.melody.memorytest;

import android.app.ActivityManager;
import android.content.Context;
import android.os.Debug;
import com.unity3d.player.UnityPlayer;

/**
 * Created by melody on 2017/1/17.
 */

public class MemoryUtil {
    /**
     * get the memory of process with certain pid.
     *
     * @param pid
     *            pid of process
     * @param context
     *            context of certain activity
     * @return memory usage of certain process
     */
    public static int getPidMemorySize(int pid,Context context) {
        ActivityManager am = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
        int[] myMempid = new int[]{pid};
        Debug.MemoryInfo[] memoryInfo = am.getProcessMemoryInfo(myMempid);
        memoryInfo[0].getTotalSharedDirty();
        int memSize = memoryInfo[0].getTotalPss();
        return memSize;
    }
    public static int getUsedMemory(){
        int pid = android.os.Process.myPid();
        Context context = UnityPlayer.currentActivity;
        return getPidMemorySize(pid,context);
    }
}

using UnityEngine;
using System.Collections;
using System.Runtime.InteropServices;


public class ProfilerGUI : MonoBehaviour {
    [DllImport("__Internal")]
    public extern static long getResidentMemory();
    float interval = 1f;
    string totalMemory = "totalMemory:";

    GUIStyle style;
    void Start(){
        style = new GUIStyle();
        style.normal.textColor = Color.green;
        style.fontSize = 30;
        StartCoroutine(GetMemoryInterval());
    }
    IEnumerator GetMemoryInterval()
    {
        yield return new WaitForSeconds(interval);
#if UNITY_EDITOR
        totalMemory = "totalMemory:" + Random.Range(100f, 200f).ToString(".00");//print fake number in UnityEditor
#elif UNITY_IOS
        totalMemory = "totalMemory:" + ((float)getResidentMemory() / 1048576).ToString(".00");
#elif UNITY_ANDROID
        AndroidJavaClass jc = new AndroidJavaClass("com.melody.memorytest.MemoryUtil");
        totalMemory = "totalMemory:" + (float)jc.CallStatic<int>("getUsedMemory") / 1024;
#endif
        StartCoroutine(GetMemoryInterval());
    }
    Rect r = new Rect(0,Screen.height - 80 ,200,80);
    void OnGUI(){
        GUI.Label (r,totalMemory,style);
    }
}