Changes

Current [[CLI/cmd/pre-dump|pre-dump]] mode is used to write task memory contents into image

Current [[CLI/cmd/pre-dump|pre-dump]] mode is used to write task memory contents into image

files w/o stopping the task for too long. It does this by stopping the task, infecting it and

files w/o stopping the task for too long. It does this by stopping the task, infecting it and

draining all the memory into a set of pipes. Then the task is cured and resumed and the pipes'

draining all the memory into a set of pipes. Then the task is cured, resumed and the pipes'

contents is written into images (maybe a [[page server]]). This approach creates a big stress

contents is written into images (maybe a [[page server]]). Unfortunately, this approach creates

on memory subsystem, as keeping all the memory in pipes creates a lot of unreclaimable memory

a big stress on the memory subsystem, as keeping all memory in pipes creates a lot of unreclaimable

(pages in pipes are not swappable), as well as the number of pipes themselves can be buge (as

memory (pages in pipes are not swappable), as well as the number of pipes themselves can be huge, as

one pipe doesn't store more than a fixed certain amount of data).

one pipe doesn't store more than a fixed amount of data (see pipe(7) man page).

We can try to use sys_read_process_vm() syscall to mitigate all of the above. To do this we

A solution for this problem is to use a sys_read_process_vm() syscall, which will mitigate

need to allocate a temporary buffer in criu, then walk the target process vm by copying the

all of the above. To do this we need to allocate a temporary buffer in criu, then walk the

memory piece-by-piece into it, then flush the data into image (or page server), then repeat.

target process vm by copying the memory piece-by-piece into it, then flush the data into image

(or page server), and repeat.

Ideally there should be sys_splice_process_vm() syscall in the kernel, that does the same as

Ideally there should be sys_splice_process_vm() syscall in the kernel, that does the same as