From: Hannu Nyman <hannu.nyman@iki.fi>
Date: Tue, 24 Nov 2020 06:39:48 +0000 (+0200)
Subject: base-files: flush kernel memory cache during sysupgrade
X-Git-Tag: v21.02.0-rc1~777
X-Git-Url: http://git.openwrt.org/?a=commitdiff_plain;h=3d12b47985fc1983849925d2dc23430f55210c80;p=openwrt%2Fopenwrt.git

base-files: flush kernel memory cache during sysupgrade

Flush kernel memory caches during sysupgrade in order
to mitigate the impact from memory consumption spikes
in low-RAM devices.

This may help to prevent sysupgrade causing a reboot
before the actual flashing starts.

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>
---

diff --git a/package/base-files/files/lib/upgrade/common.sh b/package/base-files/files/lib/upgrade/common.sh
index a5c27dc2fb..b44a5998f4 100644
--- a/package/base-files/files/lib/upgrade/common.sh
+++ b/package/base-files/files/lib/upgrade/common.sh
@@ -297,6 +297,7 @@ indicate_upgrade() {
 # $(2): (optional) pipe command to extract firmware, e.g. dd bs=n skip=m
 default_do_upgrade() {
 	sync
+	echo 3 > /proc/sys/vm/drop_caches
 	if [ -n "$UPGRADE_BACKUP" ]; then
 		get_image "$1" "$2" | mtd $MTD_ARGS $MTD_CONFIG_ARGS -j "$UPGRADE_BACKUP" write - "${PART_NAME:-image}"
 	else
diff --git a/package/base-files/files/lib/upgrade/stage2 b/package/base-files/files/lib/upgrade/stage2
index c7629c383f..23d356a447 100755
--- a/package/base-files/files/lib/upgrade/stage2
+++ b/package/base-files/files/lib/upgrade/stage2
@@ -123,6 +123,7 @@ kill_remaining KILL 1
 
 sleep 1
 
+echo 3 > /proc/sys/vm/drop_caches
 
 if [ -n "$IMAGE" ] && type 'platform_pre_upgrade' >/dev/null 2>/dev/null; then
 	platform_pre_upgrade "$IMAGE"