From: Huang Ying <ying.huang@xxxxxxxxx> MADV_FREE is a lazy free mechanism in Linux. According to the manpage of mavise(2), the semantics of MADV_FREE is, The application no longer requires the pages in the range specified by addr and len. The kernel can thus free these pages, but the freeing could be delayed until memory pressure occurs. ... Originally, the pages freed lazily by MADV_FREE will only be freed really by page reclaiming when there is memory pressure or when unmapping the address range. In addition to that, there's another opportunity to free these pages really, when we try to migrate them. The main value to do that is to avoid to create the new memory pressure immediately if possible. Instead, even if the pages are required again, they will be allocated gradually on demand. That is, the memory will be allocated lazily when necessary. This follows the common philosophy in the Linux kernel, allocate resources lazily on demand. This patchset implement this in addition to some cleanup to migration and MADV_FREE code. Best Regards, Huang, Ying
