Changes

* /proc/pid/smaps file and /proc/pid/map_files/ directory with links are used to determine

* /proc/pid/smaps file and /proc/pid/map_files/ directory with links are used to determine

** memory areas in use by task

** memory areas in use by task

** file is mapped (if any)

** mapped files (if any)

** shared memory "identifier" to resolve the MAP_SHARED areas

** shared memory "identifier" to resolve the MAP_SHARED areas

* /proc/pid/pagemap file that reveals important flags

* /proc/pid/pagemap file that reveals important flags

* Ptrace SEIZE, used to grab pages from task's VM into a pipe (with vmsplice)

* Ptrace SEIZE, used to grab pages from task's VM into a pipe (with vmsplice)

The last step deserves a more detailed explanation. In order to drain memory from a task, we first generate the bitmap of pages needed to be dumped (using the smaps, map_files and pagemap from proc). Next, we create a set of pipes to put pages into. Then we infect the process with [[parasite code]], which, in turn, gets the pipes and <code>vmsplice</code>s the required pages into it. Finally, we <code>splice</code> the pages from pipes into [[memory dumps|image files]].

The last step deserves a more detailed explanation. In order to drain memory from a task, we first generate the bitmap of pages needed to be dumped (using the smaps, map_files and [[pagemap cache]] filled from proc). Next, we create a set of pipes to put pages into. Then we infect the process with [[parasite code]], which, in turn, gets the pipes and <code>vmsplice</code>s the required pages into it. Finally, we <code>splice</code> the pages from pipes into [[memory dumps|image files]].

=== Restoring ===

=== Restoring ===

* [[Memory changes tracking]]

* [[Memory changes tracking]]

* [[Shared memory]]

* [[Shared memory]]

* [[Disk-less migration]]

* [[Disk-less migration]]

* [[Page server]]

* [[Page server]]

[[Category:Memory]]

[[Category:Memory]]

[[Category:Live migration]]

[[Category:Live migration]]