title: eglSwapBuffers suddenly takes much longer time to finish
body: <p>Today i found my opengles program frame time sometimes increases for unknown reason, usually its 16ms, but sometimes it will take 33ms to finish one frame. after hours profiling and researching i found the reason : the frame time increase is because the 'eglSwapBuffers' takes much longer time than usual. usually time spend on 'eglSwapBuffers' is less than 10 milliseconds, but sometimes it will take about 26 milliseconds.</p>
  
  <p>the scene is static so the frame time is supposed to be stable?</p>
  
  <p>Would anybody know the reason please help, what should i do to make my frame time stable?</p>