cmd/btrfs-rec inspect rebuild-nodes: Optimize memory use

2 files changed, 20 insertions, 9 deletions

diff --git a/cmd/btrfs-rec/inspect_rebuildnodes.go b/cmd/btrfs-rec/inspect_rebuildnodes.go
index 9c86c3a..d813f36 100644
--- a/cmd/btrfs-rec/inspect_rebuildnodes.go
+++ b/cmd/btrfs-rec/inspect_rebuildnodes.go
@@ -5,7 +5,10 @@
 package main
 
 import (
+	"context"
 	"os"
+	"runtime"
+	"time"
 
 	"git.lukeshu.com/go/lowmemjson"
 	"github.com/datawire/dlib/dlog"
@@ -15,6 +18,7 @@ import (
 	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs"
 	"git.lukeshu.com/btrfs-progs-ng/lib/btrfsprogs/btrfsinspect"
 	"git.lukeshu.com/btrfs-progs-ng/lib/btrfsprogs/btrfsinspect/rebuildnodes"
+	"git.lukeshu.com/btrfs-progs-ng/lib/textui"
 )
 
 func init() {
@@ -26,18 +30,25 @@ func init() {
 		RunE: func(fs *btrfs.FS, cmd *cobra.Command, args []string) error {
 			ctx := cmd.Context()
 
-			dlog.Infof(ctx, "Reading %q...", args[0])
-			nodeScanResults, err := readJSONFile[btrfsinspect.ScanDevicesResult](ctx, args[0])
-			if err != nil {
-				return err
-			}
-			dlog.Infof(ctx, "... done reading %q", args[0])
+			// This is wrapped in a func in order to *ensure* that `nodeScanResults` goes out of scope once
+			// `rebuilder` has been created.
+			rebuilder, err := func(ctx context.Context) (rebuildnodes.Rebuilder, error) {
+				dlog.Infof(ctx, "Reading %q...", args[0])
+				nodeScanResults, err := readJSONFile[btrfsinspect.ScanDevicesResult](ctx, args[0])
+				if err != nil {
+					return nil, err
+				}
+				dlog.Infof(ctx, "... done reading %q", args[0])
 
-			rebuilder, err := rebuildnodes.NewRebuilder(ctx, fs, nodeScanResults)
+				return rebuildnodes.NewRebuilder(ctx, fs, nodeScanResults)
+			}(ctx)
 			if err != nil {
 				return err
 			}
 
+			runtime.GC()
+			time.Sleep(textui.LiveMemUseUpdateInterval) // let the logs reflect that GC right away
+
 			dlog.Info(ctx, "Rebuilding node tree...")
 			rebuildErr := rebuilder.Rebuild(ctx)
 			dst := os.Stdout
diff --git a/lib/textui/log_memstats.go b/lib/textui/log_memstats.go
index 6e3c3a1..7ef35da 100644
--- a/lib/textui/log_memstats.go
+++ b/lib/textui/log_memstats.go
@@ -19,14 +19,14 @@ type LiveMemUse struct {
 
 var _ fmt.Stringer = (*LiveMemUse)(nil)
 
-var liveMemUseUpdateInterval = Tunable(1 * time.Second)
+var LiveMemUseUpdateInterval = Tunable(1 * time.Second)
 
 func (o *LiveMemUse) String() string {
 	o.mu.Lock()
 
 	// runtime.ReadMemStats() calls stopTheWorld(), so we want to
 	// rate-limit how often we call it.
-	if now := time.Now(); now.Sub(o.last) > liveMemUseUpdateInterval {
+	if now := time.Now(); now.Sub(o.last) > LiveMemUseUpdateInterval {
 		runtime.ReadMemStats(&o.stats)
 		o.last = now
 	}