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, 12 insertions, 4 deletions

diff --git a/libpod/container_api.go b/libpod/container_api.go
index 38223316e..b0ea7c0de 100644
--- a/libpod/container_api.go
+++ b/libpod/container_api.go
@@ -794,21 +794,29 @@ type ContainerCheckpointOptions struct {
 	// container no PID 1 will be in the namespace and that is not
 	// possible.
 	Pod string
+	// PrintStats tells the API to fill out the statistics about
+	// how much time each component in the stack requires to
+	// checkpoint a container.
+	PrintStats bool
 }
 
 // Checkpoint checkpoints a container
-func (c *Container) Checkpoint(ctx context.Context, options ContainerCheckpointOptions) error {
+// The return values *define.CRIUCheckpointRestoreStatistics and int64 (time
+// the runtime needs to checkpoint the container) are only set if
+// options.PrintStats is set to true. Not setting options.PrintStats to true
+// will return nil and 0.
+func (c *Container) Checkpoint(ctx context.Context, options ContainerCheckpointOptions) (*define.CRIUCheckpointRestoreStatistics, int64, error) {
 	logrus.Debugf("Trying to checkpoint container %s", c.ID())
 
 	if options.TargetFile != "" {
 		if err := c.prepareCheckpointExport(); err != nil {
-			return err
+			return nil, 0, err
 		}
 	}
 
 	if options.WithPrevious {
 		if err := c.canWithPrevious(); err != nil {
-			return err
+			return nil, 0, err
 		}
 	}
 
@@ -817,7 +825,7 @@ func (c *Container) Checkpoint(ctx context.Context, options ContainerCheckpointO
 		defer c.lock.Unlock()
 
 		if err := c.syncContainer(); err != nil {
-			return err
+			return nil, 0, err
 		}
 	}
 	return c.checkpoint(ctx, options)