Changes

Currently CRIU uses [[Memory_changes_tracking|Soft-dirty]] mechanism in Linux kernel to track memory changes.

Currently CRIU uses [[Memory_changes_tracking|Soft-dirty]] mechanism in Linux kernel to track memory changes.

This mechanism can be complemented or even completely replaced with recently proposed userfaultfd-WP.

This mechanism can be complemented (or even completely replaced) with recently proposed write protection support for

userfaultfd (userfaultfd-WP).

Userfault allows implementation of paging in userspace. It allows an application to receive notifications about page faults and provide the desired memory contents for the faulting pages. In the current upstream kernels only missing page faults are supported, but there is an ongoing work to allow notifications for write faults as well. Using these notifications it would be possible to precisely track memory accesses of during pre-dump iterations and this approach may prove more efficient than soft-dirty.

Userfault allows implementation of paging in userspace. It allows an application to receive notifications about page faults and provide the desired memory contents for the faulting pages. In the current upstream kernels only missing page faults are supported, but there is an ongoing work to allow notifications for write faults as well. Using such notifications it would be possible to precisely track memory changes during pre-dump iterations. This approach may prove to be more efficient than soft-dirty.

   

   

'''Links:'''

'''Links:'''

* [https://github.com/xzpeter/linux/tree/uffd-wp-merged Userfaultfd-WP]

* [https://github.com/xzpeter/linux/tree/uffd-wp-merged Userfaultfd-WP]

* [https://www.kernel.org/doc/html/latest/admin-guide/mm/soft-dirty.html?highlight=soft%20dirty Soft-Dirty]

* [https://www.kernel.org/doc/html/latest/admin-guide/mm/soft-dirty.html?highlight=soft%20dirty Soft-Dirty]

'''Details:'''

'''Details:'''