2,257
edits
Changes
Jump to navigation
Jump to search
Line 90:
Line 90: − + + + + + + + − * It keeps all the memory in pipes, and their number can be huge due to limited one pipe size+ − * It keeps all the memory in pipes and this memory is unreclaimable for that period+ − * It [[parasite code|stops and infects]] tasks to drain memory from+ − − − − * No pipes, just copy data into temp buffer and send − * Memory is always reclaimable − * No infection is needed, just freeze, reset the tracker and proceed
→Optimize the pre-dump algorithm
'''Summary:''' Optimize the pre-dump algorithm to avoid pinning to many memory in RAM
'''Summary:''' Optimize the pre-dump algorithm to avoid pinning to many memory in RAM
Current [[CLI/cmd/pre-dump|pre-dump]] mode suffers from several issues
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
draining all the memory into a set of pipes. Then the task is cured and resumed and the pipes'
contents is written into images (maybe a [[page server]]). This approach creates a big stress
on memory subsystem, as keeping all the memory in pipes creates a lot of unreclaimable memory
(pages in pipes are not swappable), as well as the number of pipes themselves can be buge (as
one pipe doesn't store more than a fixed certain amount of data).
We can try to use sys_read_process_vm() syscall to mitigate all of the above. To do this we
need to allocate a temporary buffer in criu, then walk the target process vm by copying the
memory piece-by-piece into it, then flush the data into image (or page server), then repeat.
We can try to use sys_read_process_vm() syscall to mitigate all of the above. Benefits:
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