> > > > + 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 from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html