Added optional container checkpointing statistics

This adds the parameter '--print-stats' to 'podman container checkpoint'.
With '--print-stats' Podman will measure how long Podman itself, the OCI
runtime and CRIU requires to create a checkpoint and print out these
information. CRIU already creates checkpointing statistics which are
just read in addition to the added measurements. In contrast to just
printing out the ID of the checkpointed container, Podman will now print
out JSON:

 # podman container checkpoint --latest --print-stats
 {
     "podman_checkpoint_duration": 360749,
     "container_statistics": [
         {
             "Id": "25244244bf2efbef30fb6857ddea8cb2e5489f07eb6659e20dda117f0c466808",
             "runtime_checkpoint_duration": 177222,
             "criu_statistics": {
                 "freezing_time": 100657,
                 "frozen_time": 60700,
                 "memdump_time": 8162,
                 "memwrite_time": 4224,
                 "pages_scanned": 20561,
                 "pages_written": 2129
             }
         }
     ]
 }

The output contains 'podman_checkpoint_duration' which contains the
number of microseconds Podman required to create the checkpoint. The
output also includes 'runtime_checkpoint_duration' which is the time
the runtime needed to checkpoint that specific container. Each container
also includes 'criu_statistics' which displays the timing information
collected by CRIU.

Signed-off-by: Adrian Reber <areber@redhat.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/libpod/oci.go b/libpod/oci.go
index c92d9a077..f78600210 100644
--- a/libpod/oci.go
+++ b/libpod/oci.go
@@ -101,8 +101,10 @@ type OCIRuntime interface {
 	// CheckpointContainer checkpoints the given container.
 	// Some OCI runtimes may not support this - if SupportsCheckpoint()
 	// returns false, this is not implemented, and will always return an
-	// error.
-	CheckpointContainer(ctr *Container, options ContainerCheckpointOptions) error
+	// error. If CheckpointOptions.PrintStats is true the first return parameter
+	// contains the number of microseconds the runtime needed to checkpoint
+	// the given container.
+	CheckpointContainer(ctr *Container, options ContainerCheckpointOptions) (int64, error)
 
 	// CheckConmonRunning verifies that the given container's Conmon
 	// instance is still running. Runtimes without Conmon, or systems where