> > > > + x_intercept = setpoint + 2 * span; > ^^ BTW, why do you have 2*span here? It can result in x_intercept being > ~3*bdi_thresh... So maybe you should use bdi_thresh/2 in the computation of > span? OK, I'll follow your suggestion to use span = 8 * write_bw, for single bdi case span = bdi_thresh, for JBOD case x_intercept = setpoint + span; It does make sense to squeeze the bdi_dirty fluctuation range a bit by doubling span and making the control line more sharp. Thanks, Fengguang -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>