改进的内存预拷贝动态迁移算法

由于预拷贝迁移算法的迭代拷贝过程存在重复地拷贝同一个内存页的问题，从而导致拷贝内存页数量的增加和总迁移时间的延长。对脏页拷贝策略进行改进，将修改频繁的脏页在停机拷贝阶段传输，从而有效地缩短总迁移时间。然而该策略的改进又导致停机拷贝阶段的页面增多而引起停机时间延长，于是采用LZO压缩算法将停机阶段待拷贝的页面先压缩再传输，通过降低待传输的数据量来缩短停机时间。在进行虚拟机迁移实验时，与预拷贝迁移算法相比，结果表明该算法在未延长停机时间的同时，缩短了总迁移时间，尤其是在高脏页率环境下，该算法明显表现出更优的迁移性能。

Improved memory pre-copy live migration method

Since the iterative copy has an issue of copying the same memory page repeatedly in pre-copy live migration method, it will make the memory page increase and the total migration time extend respectively. This paper attempts to improve the strategy of copying the dirty pages. Specially, the frequently updated page is transported in the stage of stop-and-copy, which can decrease the total migration time effectively. However, this may extend the downtime because the pages generated in the stage of stop-and-copy increase. Therefore, it utilizes the LZO method to compress the pages in the stage of stop and then transport them, which can shorten the downtime by reducing the data volume. Applying the above method to virtual machine migration, experimental results show that the method shortens the total migration time clearly comparing with the pre-copy method, especially in the case of high-rate dirty pages.