Changes

== Dumping present pages ==

== Dumping present pages ==

When dumping the contents of shared memory CRIU doesn't dump all the data. Instead, it determines which pages contain  

When dumping the contents of shared memory, CRIU does not dump all of the data. Instead, it determines which pages contain  

it and dumps only them. This is done similarly to how regular [[memory dumping and restoring]] works, i.e. by analyzing

it, and only dumps those pages. This is done similarly to how regular [[memory dumping and restoring]] works, i.e. by looking

the owners' pagemap entries for PRESENT or SWAPPED bits. But there's one feature of shmem dumps -- sometimes shmem

for PRESENT or SWAPPED bits in owners' pagemap entries.

page can exist in the kernel, but not mapped to any process. In this case criu detects one by calling mincore() on

 

the shmem segment, which reports back the page in-memory status. And the mincore bitmap is AND-ed with the per-process

There is one particular feature of shared memory dumps worth mentioning. Sometimes, a shared memory page

ones.

can exist in the kernel, but it is not mapped to any process. CRIU detects such pages by calling mincore()

on the shmem segment, which reports back the page in-memory status. The mincore bitmap is when ANDed with

the per-process ones.

== See also ==

== See also ==