build: improve resource limits output and docs

Signed-off-by: Jiří Moravčík <jiri.moravcik@gmail.com>

commands/history/inspect.go

@@ -585,10 +585,10 @@ workers0:
 		fmt.Fprintf(tw, "Resource Limits:\t%s\n", out.Config.Ulimit)
 	}
 	if out.Config.Memory != "" {
-		fmt.Fprintf(tw, "Memory:\t%s\n", out.Config.Memory)
+		fmt.Fprintf(tw, "Memory:\t%s\n", humanizeBytes(out.Config.Memory))
 	}
 	if out.Config.MemorySwap != "" {
-		fmt.Fprintf(tw, "Memory Swap:\t%s\n", out.Config.MemorySwap)
+		fmt.Fprintf(tw, "Memory Swap:\t%s\n", humanizeBytes(out.Config.MemorySwap))
 	}
 	if out.Config.CPUShares != "" {
 		fmt.Fprintf(tw, "CPU Shares:\t%s\n", out.Config.CPUShares)

commands/history/utils.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/docker/buildx/builder"
 	"github.com/docker/cli/cli/command"
+	"github.com/docker/go-units"
 	controlapi "github.com/moby/buildkit/api/services/control"
 	"github.com/moby/buildkit/frontend/dockerfile/dfgitutil"
 	"github.com/pkg/errors"
@@ -192,6 +193,17 @@ func formatDuration(d time.Duration) string {
 	return fmt.Sprintf("%dm %2ds", int(d.Minutes()), int(d.Seconds())%60)
 }
 
+// humanizeBytes formats a raw byte-count string (as stored in the frontend
+// attributes) into a human-readable size. Non-numeric values such as "-1"
+// (unlimited swap) are returned unchanged.
+func humanizeBytes(v string) string {
+	n, err := strconv.ParseInt(v, 10, 64)
+	if err != nil || n < 0 {
+		return v
+	}
+	return units.BytesSize(float64(n))
+}
+
 type matchFunc func(*controlapi.BuildHistoryRecord) bool
 
 func dockerFiltersToBuildkit(in []string) ([]string, []matchFunc, error) {