From f1b73c9301bd35388f058dcd202358ce1c85a40b Mon Sep 17 00:00:00 2001
From: Michael Eischer <michael.eischer@fau.de>
Date: Fri, 2 Jun 2023 21:51:50 +0200
Subject: [PATCH 1/4] Reduce GOGC to 50

The index used by restic consumes a major part of the total memory
usage. This leads to an unnecessarily large amount of memory that
contains ephemeral objects that are only used for a short time.
---
 cmd/restic/main.go | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/cmd/restic/main.go b/cmd/restic/main.go
index 392177d13..64b75b43a 100644
--- a/cmd/restic/main.go
+++ b/cmd/restic/main.go
@@ -7,6 +7,7 @@ import (
 	"log"
 	"os"
 	"runtime"
+	godebug "runtime/debug"
 
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/options"
@@ -81,7 +82,16 @@ func needsPassword(cmd string) bool {
 
 var logBuffer = bytes.NewBuffer(nil)
 
+func tweakGoGC() {
+	// lower GOGC from 100 to 50, unless it was manually overwritten by the user
+	oldValue := godebug.SetGCPercent(50)
+	if oldValue != 100 {
+		godebug.SetGCPercent(oldValue)
+	}
+}
+
 func main() {
+	tweakGoGC()
 	// install custom global logger into a buffer, if an error occurs
 	// we can show the logs
 	log.SetOutput(logBuffer)

From eef0ee7a85994e4696368e39d8f7d13e07017115 Mon Sep 17 00:00:00 2001
From: Michael Eischer <michael.eischer@fau.de>
Date: Fri, 2 Jun 2023 21:56:14 +0200
Subject: [PATCH 2/4] repository: trigger GC after loading the index

Loading the index requires some scratch space, thus make sure that this
memory does not factor into the targeted gc memory usage limit.
---
 internal/repository/repository.go | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/internal/repository/repository.go b/internal/repository/repository.go
index 9d1b40c64..653c1f774 100644
--- a/internal/repository/repository.go
+++ b/internal/repository/repository.go
@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"runtime"
 	"sort"
 	"sync"
 
@@ -601,6 +602,9 @@ func (r *Repository) LoadIndex(ctx context.Context) error {
 		return err
 	}
 
+	// Trigger GC to reset garbage collection threshold
+	runtime.GC()
+
 	if r.cfg.Version < 2 {
 		// sanity check
 		ctx, cancel := context.WithCancel(ctx)

From 2fcb3947df77427cafdb613acd831d9cbc111530 Mon Sep 17 00:00:00 2001
From: Michael Eischer <michael.eischer@fau.de>
Date: Fri, 2 Jun 2023 21:57:40 +0200
Subject: [PATCH 3/4] prune: trigger GC after prune planning

---
 cmd/restic/cmd_prune.go | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/cmd/restic/cmd_prune.go b/cmd/restic/cmd_prune.go
index 26f21b1f3..1889dffd6 100644
--- a/cmd/restic/cmd_prune.go
+++ b/cmd/restic/cmd_prune.go
@@ -3,6 +3,7 @@ package main
 import (
 	"context"
 	"math"
+	"runtime"
 	"sort"
 	"strconv"
 	"strings"
@@ -205,6 +206,9 @@ func runPruneWithRepo(ctx context.Context, opts PruneOptions, gopts GlobalOption
 		return err
 	}
 
+	// Trigger GC to reset garbage collection threshold
+	runtime.GC()
+
 	return doPrune(ctx, opts, gopts, repo, plan)
 }
 

From 0f80b6a137e0ffd79dce0887be457d62c0c826db Mon Sep 17 00:00:00 2001
From: Michael Eischer <michael.eischer@fau.de>
Date: Thu, 8 Jun 2023 18:02:46 +0200
Subject: [PATCH 4/4] add changelog for gc tuning

---
 changelog/unreleased/issue-3328 | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 changelog/unreleased/issue-3328

diff --git a/changelog/unreleased/issue-3328 b/changelog/unreleased/issue-3328
new file mode 100644
index 000000000..a8ef76d79
--- /dev/null
+++ b/changelog/unreleased/issue-3328
@@ -0,0 +1,5 @@
+Enhancement: Reduce memory usage by up to 25%
+
+https://github.com/restic/restic/issues/3328
+https://github.com/restic/restic/pull/4352
+https://github.com/restic/restic/pull/4353