Hi Dave, I am now working on how to benefit post-copy by skipping the free pages, and I remember you have said we should let the destination know the info of free pages so as to avoid request the free pages from the source. We have two solutions: a. send the migration dirty page bitmap to destination before post copy start, so the destination can decide whether to request the pages or place zero pages by checking the migration dirty page bitmap. The advantage is that we can avoid sending the free pages. the disadvantage is that we have to send extra data to destination. b. Check the page request on the source side, if it's not a dirty page, send a zero page header to the destination. What's your opinion about them? Liang -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html