Postcopy migration is a mature technology in virtualization. However the performance of postcopy is not stable. We find many memory intensive loads having a high proportion of independent fixed-size data (FSD) cases. To improve migration performance, we present DP: an algorithm which applies to intelligently tackle FSD load during postcopy migration. We implement DP as an online algorithm triggered by remote paging, and adjusting to prepage the most appropriate amount of pages related to recent page fault records. DP also has a threshold processing mechanism to prevent from noise which is derived from load size fluctuation. The experimental results show that DP algorithm can significantly reduce response time and implicit downtime in postcopy migration, with an high improvement on QoS.