CRIU can use two mechanisms to detect page changes. One is the soft-dirty kernel feature which is mainlined and can be accessed via /proc/PID/pagemap [1]. The o

CRIU can use two mechanisms to detect page changes. One is the soft-dirty kernel feature which is mainlined and can be accessed via /proc/PID/pagemap [1]. The other is userfaultfd which is only partially merged in the newest kernel. userfaultfd lacks write detection which the article mentioned. My understanding is that using pagemap requires the entire process to be frozen while it is scanned for memory changes and the memory is copied while uffd allows for a more streaming/on-demand approach that doesn't require stopping the entire process. [1] https://www.kernel.org/doc/Documentation/vm/soft-dirty.txt https://www.kernel.org/doc/Documentation/vm/soft-dirty.txt