perf(bootstrap): k3s 以 GOGC=50 运行，Velocity 1G 以内改用串行回收和 C1，基础设施空载压到约 1 GB

deploy/bootstrap.sh

@@ -502,6 +502,9 @@ K3S_REGISTRIES_FILE="/etc/rancher/k3s/registries.yaml"
 # client certificate are variables for the same reason as the file above.
 K3S_CONFIG_DROPIN="/etc/rancher/k3s/config.yaml.d/50-felis.yaml"
 K3S_UNIT_FILE="/etc/systemd/system/k3s.service"
+# The installer's environment for the k3s service (write_k3s_service_dropin); k3s's own
+# installer rewrites the unit and its .env file, never this.
+K3S_SERVICE_DROPIN="/etc/systemd/system/k3s.service.d/50-felis.conf"
 K3S_KUBECONFIG="/etc/rancher/k3s/k3s.yaml"
 K3S_KUBELET_CERT="/var/lib/rancher/k3s/agent/client-kubelet.crt"
 # Where k3s imports image tarballs from as it starts (stage_k3s_airgap_images).
@@ -1937,9 +1940,10 @@ configure_k3s_firewall() {
 
 install_k3s() {
   configure_k3s_firewall
-  # Before the installer runs: a fresh k3s reads the drop-in on its first start.
+  # Before the installer runs: a fresh k3s reads both drop-ins on its first start.
   K3S_RESTART_NEEDED=0
   write_k3s_config
+  write_k3s_service_dropin
 
   local installer_ran=0
   if [ -x "$K3S_BIN" ]; then
@@ -1969,7 +1973,7 @@ install_k3s() {
   # The installer restarts k3s itself; otherwise a changed drop-in or unit takes a
   # restart to load. Pods keep running across it (k3s leaves the containers be).
   if [ "$K3S_RESTART_NEEDED" = 1 ] && [ "$installer_ran" = 0 ]; then
-    log "restarting k3s to load its new settings (${K3S_CONFIG_DROPIN})"
+    log "restarting k3s to load its new settings (${K3S_CONFIG_DROPIN}, ${K3S_SERVICE_DROPIN})"
     systemctl restart k3s
   fi
   export KUBECONFIG="$K3S_KUBECONFIG"
@@ -2039,6 +2043,37 @@ write_k3s_config() {
   log "wrote ${file}${name:+ (node name pinned to ${name})}"
 }
 
+# write_k3s_service_dropin runs k3s, and the containerd it starts with its own environment,
+# with the Go collector at half the default heap growth (GOGC=50). An idle k3s holds about
+# 150 MiB live and by default lets its heap reach twice that before collecting; at 50 it
+# collects at one and a half times. Measured on the verification host: k3s 430 -> 370 MiB and
+# its containerd 114 -> 104 MiB, for about 2% of one core more while idle. It sets
+# K3S_RESTART_NEEDED when the file changed, since k3s reads its environment only as it starts.
+write_k3s_service_dropin() {
+  local file="$K3S_SERVICE_DROPIN" tmp
+  mkdir -p "$(dirname "$file")"
+  # Beside its destination, like write_k3s_config's; systemd reads only *.conf from the
+  # directory, so the temp name is never loaded.
+  tmp="$(mktemp "${file}.XXXXXX")"
+  remember_temp "$tmp"
+  {
+    echo "# Written by the Felis installer (deploy/bootstrap.sh); a rerun rewrites it."
+    echo "[Service]"
+    echo "Environment=GOGC=50"
+  } > "$tmp"
+  if [ -f "$file" ] && cmp -s "$tmp" "$file"; then
+    rm -f "$tmp"
+    restore_label "$file"
+    ok "k3s service environment already current"
+    return 0
+  fi
+  chmod 0644 "$tmp"
+  mv "$tmp" "$file"
+  systemctl daemon-reload
+  K3S_RESTART_NEEDED=1
+  log "wrote ${file} (GOGC=50)"
+}
+
 # A command-line flag outranks every config file, and k3s's installer writes
 # INSTALL_K3S_EXEC into the unit's ExecStart one quoted word per line, so installs from
 # before the drop-in keep "'--write-kubeconfig-mode' \" followed by "'644' \" there.
@@ -3865,12 +3900,21 @@ install_velocity_service() {
   # sees it -- unquoted, that spelling would hand java a stray "legacy112" argument and the unit
   # would not start. Quoting keeps the whole property one argv item.
   local legacy_forwarding_servers="${FELIS_LEGACY_FORWARDING_SERVERS}"
-  # The heap starts small and is not pre-touched. The proxy with its Via plugins holds about 50M
-  # live; a pre-touched 512M start kept ~0.7 GB resident on an idle network, ~0.25 GB without
-  # (measured on the verification host). The heap grows toward -Xmx as players arrive, and the
-  # periodic collection hands the growth back once they have left. FELIS_VELOCITY_XMX is at
-  # least 256M, so the start never exceeds the ceiling.
-  local xmx="$FELIS_VELOCITY_XMX" xms="64M"
+  # The heap starts small and is not pre-touched: the proxy with its Via plugins holds about 50M
+  # live, and a pre-touched 512M start kept ~0.7 GB resident on an idle network. Up to a 1G
+  # ceiling (the default, sized for about 100 players) it runs the serial collector and only the
+  # C1 compiler, 173 MiB idle against 267 MiB under G1 (both measured on the verification host);
+  # with that little live, a young collection takes milliseconds, and the proxy's compression
+  # and encryption run in Velocity's native library whichever compiler is on. A larger ceiling
+  # is for a network where a serial full collection over a big heap would stall every player at
+  # once, so it keeps G1, whose periodic collection hands the growth back once players have left.
+  # FELIS_VELOCITY_XMX is at least 256M, so the start never exceeds the ceiling.
+  local xmx="$FELIS_VELOCITY_XMX" jvm
+  if [ "$(heap_megabytes "$xmx")" -le 1024 ]; then
+    jvm="-Xms16M -Xmx${xmx} -XX:+UseSerialGC -XX:TieredStopAtLevel=1"
+  else
+    jvm="-Xms64M -Xmx${xmx} -XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:G1PeriodicGCInterval=60000"
+  fi
   cat > "$VELOCITY_SERVICE" <<EOF
 [Unit]
 Description=Felis Velocity proxy (Mojang authentication + modern forwarding)
@@ -3882,7 +3926,7 @@ Type=simple
 User=${VELOCITY_USER}
 Group=${VELOCITY_USER}
 WorkingDirectory=${VELOCITY_DIR}
-ExecStart=${JRE_DIR}/bin/java -Xms${xms} -Xmx${xmx} -XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:G1PeriodicGCInterval=60000 -Dmojang.sessionserver=http://${api_ip}:8081/session/minecraft/hasJoined "-Dfelis.legacy-forwarding.servers=${legacy_forwarding_servers}" -jar ${VELOCITY_DIR}/velocity.jar
+ExecStart=${JRE_DIR}/bin/java ${jvm} -Dmojang.sessionserver=http://${api_ip}:8081/session/minecraft/hasJoined "-Dfelis.legacy-forwarding.servers=${legacy_forwarding_servers}" -jar ${VELOCITY_DIR}/velocity.jar
 Restart=on-failure
 RestartSec=5
 NoNewPrivileges=yes

deploy/bootstrap_test.sh

@@ -1250,6 +1250,7 @@ run_k3s() { # installed-version pinned-version [FELIS_UPGRADE_DEPS]
     ok() { printf "OK: %s\n" "$*"; }
     configure_k3s_firewall() { :; }
     write_k3s_config() { :; }
+    write_k3s_service_dropin() { :; }
     strip_k3s_kubeconfig_mode_flag() { :; }
     run_k3s_installer() { printf "INSTALLER: %s\n" "$FELIS_K3S_VERSION"; }
     stage_k3s_airgap_images() { echo STAGE; }
@@ -2895,11 +2896,11 @@ run_velocity_service() { # is-active(0|1) [heap]
 }
 out="$(run_velocity_service 1)"
 expect "a proxy with no recorded start is restarted" "SYSTEMCTL restart felis-velocity" "$out"
-expect "the default heap starts at 64M and may grow to 1G" "java -Xms64M -Xmx1G " "$(cat "$vdir/unit")"
+expect "the default 1G ceiling runs the serial collector and C1 from a 16M start" \
+  "java -Xms16M -Xmx1G -XX:+UseSerialGC -XX:TieredStopAtLevel=1 -Dmojang" "$(cat "$vdir/unit")"
 case "$(cat "$vdir/unit")" in
-  *AlwaysPreTouch*) echo "FAIL the proxy pre-touches its heap, holding all of -Xms from the start"; fails=$((fails + 1)) ;;
-  *"-XX:G1PeriodicGCInterval="*) echo "PASS the proxy neither pre-touches its heap nor keeps growth it no longer uses" ;;
-  *) echo "FAIL the proxy has no periodic collection to hand back an idle heap"; fails=$((fails + 1)) ;;
+  *AlwaysPreTouch*|*UseG1GC*) echo "FAIL a 1G proxy pre-touches its heap or runs G1: $(grep ExecStart "$vdir/unit")"; fails=$((fails + 1)) ;;
+  *) echo "PASS a 1G proxy neither pre-touches its heap nor runs G1" ;;
 esac
 [ -s "$vdir/fp" ] && echo "PASS the restart records what the proxy runs" \
   || { echo "FAIL no fingerprint was recorded after the restart"; fails=$((fails + 1)); }
@@ -2915,9 +2916,19 @@ expect "a stopped proxy is started whatever the fingerprint" "SYSTEMCTL restart
 printf 'JAVA_VERSION="25.0.1"\n' > "$vdir/jre/release"
 expect "a patched JRE restarts the proxy" "SYSTEMCTL restart felis-velocity" "$(run_velocity_service 1)"
 expect "a new heap size restarts the proxy" "SYSTEMCTL restart felis-velocity" "$(run_velocity_service 1 3G)"
-expect "the unit carries the new ceiling" "java -Xms64M -Xmx3G " "$(cat "$vdir/unit")"
+expect "a ceiling above 1G runs G1, whose periodic collection hands idle growth back" \
+  "java -Xms64M -Xmx3G -XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:G1PeriodicGCInterval=60000 -Dmojang" "$(cat "$vdir/unit")"
+case "$(cat "$vdir/unit")" in
+  *AlwaysPreTouch*|*UseSerialGC*|*TieredStopAtLevel*) echo "FAIL a 3G proxy carries a small proxy's flags or pre-touches: $(grep ExecStart "$vdir/unit")"; fails=$((fails + 1)) ;;
+  *) echo "PASS a 3G proxy keeps G1 and both compilers" ;;
+esac
+run_velocity_service 1 1024M >/dev/null
+expect "1024M is still a small proxy" "java -Xms16M -Xmx1024M -XX:+UseSerialGC " "$(cat "$vdir/unit")"
+run_velocity_service 1 1025M >/dev/null
+expect "a megabyte past 1G is a large one" "java -Xms64M -Xmx1025M -XX:+UseG1GC " "$(cat "$vdir/unit")"
 run_velocity_service 1 384M >/dev/null
-expect "a small ceiling keeps the same small start" "java -Xms64M -Xmx384M " "$(cat "$vdir/unit")"
+expect "a small ceiling runs the small proxy's flags" \
+  "java -Xms16M -Xmx384M -XX:+UseSerialGC -XX:TieredStopAtLevel=1 -Dmojang" "$(cat "$vdir/unit")"
 # `felis rotate-token velocity` rewrites service-token, which the plugin re-reads by itself:
 # that line alone changing leaves the proxy running, and any other change restarts it.
 props="$vdir/v/plugins/felis-link/felis-link.properties"
@@ -3015,10 +3026,7 @@ expect "a heap in megabytes is kept" "768" "$(heap 768m)"
 for bad in 1 1K 0G 01G G -1G 1.5G 9999999G; do
   expect "the heap spelling '$bad' is refused" "0" "$(heap "$bad")"
 done
-case "$(awk '/^install_velocity_service\(\) \{/,/^}/' "$BS")" in
-  *'-Xms${xms} -Xmx${xmx} '*) echo "PASS the proxy unit takes its heap from FELIS_VELOCITY_XMX" ;;
-  *) echo "FAIL the proxy unit's heap is not FELIS_VELOCITY_XMX"; fails=$((fails + 1)) ;;
-esac
+# The unit written for each ceiling is checked with the rerun tests above.
 
 # --- reproducible image ids ---------------------------------------------------------------
 # restart_existing_system_servers compares image ids across runs; a default BuildKit
@@ -3230,6 +3238,63 @@ out="$(run_k3s_config "$kdir/broken.crt" "$kdir/k3s" renamed-host)"
 expect "a certificate openssl cannot parse is a warning, not a failed install" "WARN: could not read this node's k3s name" "$out"
 expect "and the drop-in is still written" 'write-kubeconfig-mode: "0600"' "$(cat "$dropin")"
 
+# k3s's Go collector runs at GOGC=50 through a systemd drop-in, written beside itself and
+# loaded (with a k3s restart) only when it changed.
+svblock="$(awk '/^write_k3s_service_dropin\(\) \{/,/^}/' "$BS")"
+[ -n "$svblock" ] || { echo "FAIL: no write_k3s_service_dropin found in $BS"; exit 1; }
+svdropin="$kdir/k3s.service.d/50-felis.conf"
+run_k3s_service_dropin() {
+  DROPIN="$svdropin" bash -c '
+    set -Eeuo pipefail
+    ok() { echo "OK: $*"; }; log() { echo "LOG: $*"; }
+    remember_temp() { :; }
+    restore_label() { echo "RELABEL: $*"; }
+    systemctl() { echo "SYSTEMCTL: $*"; }
+    mktemp() { local p; p="$(command mktemp "$@")"; echo "MKTEMP: $(dirname "$p")" >&2; echo "$p"; }
+    K3S_SERVICE_DROPIN="$DROPIN"
+    '"$svblock"'
+    K3S_RESTART_NEEDED=0
+    write_k3s_service_dropin
+    echo "RESTART=$K3S_RESTART_NEEDED"' 2>&1
+}
+out="$(run_k3s_service_dropin)"
+if [ "$(cat "$svdropin")" = '# Written by the Felis installer (deploy/bootstrap.sh); a rerun rewrites it.
+[Service]
+Environment=GOGC=50' ]; then
+  echo "PASS k3s runs its Go collector at GOGC=50"
+else
+  echo "FAIL the k3s service drop-in is:"; cat "$svdropin"; fails=$((fails + 1))
+fi
+expect "a new service drop-in is loaded" "SYSTEMCTL: daemon-reload" "$out"
+expect "a new service drop-in asks for a k3s restart" "RESTART=1" "$out"
+if [ "$(printf '%s\n' "$out" | sed -n 's/^MKTEMP: //p' | sort -u)" = "$kdir/k3s.service.d" ]; then
+  echo "PASS the service drop-in is made beside itself, never under /tmp"
+else
+  echo "FAIL temporary files for the service drop-in were made in: $(printf '%s\n' "$out" | sed -n 's/^MKTEMP: //p')"; fails=$((fails + 1))
+fi
+if [ "$(stat -c %a "$svdropin" 2>/dev/null || stat -f %Lp "$svdropin")" = 644 ]; then
+  echo "PASS the service drop-in is readable like the unit it extends"
+else
+  echo "FAIL the service drop-in must be 0644"; fails=$((fails + 1))
+fi
+out="$(run_k3s_service_dropin)"
+expect "an unchanged service drop-in restarts nothing" "RESTART=0" "$out"
+expect "an unchanged service drop-in says so" "OK: k3s service environment already current" "$out"
+case "$out" in
+  *daemon-reload*) echo "FAIL an unchanged service drop-in must not reload systemd"; fails=$((fails + 1)) ;;
+  *) echo "PASS an unchanged service drop-in reloads nothing" ;;
+esac
+expect "an unchanged service drop-in is still relabelled" "RELABEL: $svdropin" "$out"
+if [ "$(ls "$kdir/k3s.service.d")" = "50-felis.conf" ]; then
+  echo "PASS no temporary file is left beside the service drop-in"
+else
+  echo "FAIL k3s.service.d holds: $(ls "$kdir/k3s.service.d")"; fails=$((fails + 1))
+fi
+printf '[Service]\nEnvironment=GOGC=100\n' > "$svdropin"
+out="$(run_k3s_service_dropin)"
+expect "an edited service drop-in is put back" "Environment=GOGC=50" "$(cat "$svdropin")"
+expect "and k3s is restarted onto it" "RESTART=1" "$out"
+
 sblock="$(awk '/^strip_k3s_kubeconfig_mode_flag\(\) \{/,/^}/' "$BS")"
 [ -n "$sblock" ] || { echo "FAIL: no strip_k3s_kubeconfig_mode_flag found in $BS"; exit 1; }
 # ExecStart as k3s's installer writes it (copied off an install made with the old flag).
@@ -3290,17 +3355,19 @@ iblock="$(awk '/^install_k3s\(\) \{/,/^}/' "$BS")"
 iblock="$iblock
 $(awk '/^version_newer\(\) \{/,/^}/' "$BS")
 $(awk '/^k3s_upgrade_allowed\(\) \{/,/^}/' "$BS")"
-run_install_k3s() { # $1: installed version ("" = none), $2: drop-in changed (0|1), $3: FELIS_UPGRADE_DEPS
-  INSTALLED="$1" CHANGED="$2" UPGRADE="${3:-0}" KDIR="$kdir" bash -c '
+run_install_k3s() { # $1: installed version ("" = none), $2: config drop-in changed (0|1), $3: FELIS_UPGRADE_DEPS, $4: service drop-in changed (0|1)
+  INSTALLED="$1" CHANGED="$2" UPGRADE="${3:-0}" SVC_CHANGED="${4:-0}" KDIR="$kdir" bash -c '
     set -Eeuo pipefail
     ok() { echo "OK: $*"; }; log() { echo "LOG: $*"; }; warn() { echo "WARN: $*"; }
     die() { echo "DIE: $*"; exit 1; }
     FELIS_K3S_VERSION=v1.36.4+k3s1 FELIS_UPGRADE_DEPS="$UPGRADE" K3S_BIN_DIR="$KDIR" K3S_BIN="$KDIR/k3s-under-test"
     K3S_CONFIG_DROPIN=/etc/rancher/k3s/config.yaml.d/50-felis.yaml K3S_KUBECONFIG=/etc/rancher/k3s/k3s.yaml
+    K3S_SERVICE_DROPIN=/etc/systemd/system/k3s.service.d/50-felis.conf
     rm -f "$K3S_BIN"
     if [ -n "$INSTALLED" ]; then printf "#!/bin/sh\necho \"k3s version %s (abc)\"\n" "$INSTALLED" > "$K3S_BIN"; chmod +x "$K3S_BIN"; fi
     configure_k3s_firewall() { :; }
     write_k3s_config() { [ "$CHANGED" = 0 ] || K3S_RESTART_NEEDED=1; }
+    write_k3s_service_dropin() { echo "SERVICE-DROPIN"; [ "$SVC_CHANGED" = 0 ] || K3S_RESTART_NEEDED=1; }
     strip_k3s_kubeconfig_mode_flag() { :; }
     run_k3s_installer() { echo "INSTALLER"; printf "#!/bin/sh\n" > "$K3S_BIN"; command chmod +x "$K3S_BIN"; }
     stage_k3s_airgap_images() { echo "STAGE"; }
@@ -3316,9 +3383,12 @@ expect "the admin kubeconfig is made root-only once the node is up" "READY
 CHMOD: 0600 /etc/rancher/k3s/k3s.yaml" "$out"
 out="$(run_install_k3s v1.36.4+k3s1 0)"
 case "$out" in *"restart k3s"*) echo "FAIL unchanged k3s settings must not restart k3s"; fails=$((fails + 1)) ;; *) echo "PASS unchanged k3s settings restart nothing" ;; esac
+expect "a new service environment alone restarts a running k3s" "SYSTEMCTL: restart k3s" "$(run_install_k3s v1.36.4+k3s1 0 0 1)"
 out="$(run_install_k3s "" 1)"
 expect "a fresh host runs the k3s installer and waits for the node" "INSTALLER
 SYSTEMCTL: enable --now k3s" "$out"
+expect "a fresh k3s has its service environment before its first start" "SERVICE-DROPIN INSTALLER " \
+  "$(printf '%s\n' "$out" | grep -E '^(SERVICE-DROPIN|INSTALLER)$' | tr '\n' ' ')"
 expect "a fresh host stages k3s's images before k3s first starts" "STAGE
 INSTALLER" "$out"
 expect "a fresh host's kubeconfig is made root-only too" "CHMOD: 0600 /etc/rancher/k3s/k3s.yaml" "$out"

deploy/uninstall.sh

@@ -321,6 +321,16 @@ stop_database_pod() {
     || warn "${PG_DEPLOYMENT} did not stop within 2 minutes; its cluster recovers from its WAL on the next start"
 }
 
+# remove_k3s_service_dropin deletes the environment the installer gives the k3s service
+# (bootstrap.sh, write_k3s_service_dropin). k3s-uninstall.sh removes the unit and its .env
+# file and leaves the unit's drop-in directory.
+remove_k3s_service_dropin() {
+  [ -f "${UNIT_DIR}/k3s.service.d/50-felis.conf" ] || return 0
+  rm -f "${UNIT_DIR}/k3s.service.d/50-felis.conf"
+  rmdir "${UNIT_DIR}/k3s.service.d" 2>/dev/null || true
+  ok "k3s service environment removed"
+}
+
 remove_k3s() {
   local stamp
   [ "$PURGE" = 1 ] || stop_database_pod
@@ -336,6 +346,7 @@ remove_k3s() {
   if [ -x "${K3S_BIN_DIR}/k3s-uninstall.sh" ]; then
     log "running k3s-uninstall.sh"
     "${K3S_BIN_DIR}/k3s-uninstall.sh" >/dev/null 2>&1 || warn "k3s-uninstall.sh reported an error; check /var/lib/rancher and /etc/rancher"
+    remove_k3s_service_dropin
     ok "k3s removed"
   else
     warn "k3s is at ${K3S_BIN_DIR}/k3s but ${K3S_BIN_DIR}/k3s-uninstall.sh is missing; remove k3s by hand"
@@ -522,6 +533,8 @@ main() {
   case "$K3S_MODE" in
     remove) remove_k3s ;;
     keep) remove_from_cluster ;;
+    # k3s was removed some other way; what it left of the installer's goes too.
+    absent) remove_k3s_service_dropin ;;
   esac
   remove_nft_tables
   remove_firewalld_rules "$game" "$nano"

deploy/uninstall_test.sh

@@ -35,6 +35,8 @@ fresh_host() {
   for u in felis-db-backup.timer felis-db-backup.service felis-velocity.service felis-postgres-firewall.service; do
     printf '[Unit]\n' > "$root/h/units/$u"
   done
+  mkdir -p "$root/h/units/k3s.service.d"
+  printf '[Service]\nEnvironment=GOGC=50\n' > "$root/h/units/k3s.service.d/50-felis.conf"
   printf '[Service]\nExecStart=/usr/local/bin/cloudflared --config %s tunnel run\n' "$root/h/etc/cloudflared.yml" \
     > "$root/h/units/cloudflared-felis.service"
   printf 'tunnel: abc\ncredentials-file: %s\n' "$root/h/cf/abc.json" > "$root/h/etc/cloudflared.yml"
@@ -155,6 +157,9 @@ refute "keep-data leaves the database alone" "DROP DATABASE" "$calls"
   || { echo "FAIL /opt/felis or the host binary is still there"; fails=$((fails + 1)); }
 [ -z "$(ls "$root/h/units")" ] && echo "PASS every Felis unit file is removed" \
   || { echo "FAIL units left: $(ls "$root/h/units")"; fails=$((fails + 1)); }
+[ ! -e "$root/h/units/k3s.service.d" ] \
+  && echo "PASS the k3s service environment k3s's uninstaller leaves is removed with its directory" \
+  || { echo "FAIL the k3s service drop-in is still there: $(ls -R "$root/h/units")"; fails=$((fails + 1)); }
 expect "the timers are disabled" "SYSTEMCTL disable --now felis-db-backup.timer" "$calls"
 expect "the velocity user is removed" "USERDEL felis-velocity" "$calls"
 expect "the run ends pointing at the reinstall steps" "Reinstall on top of kept data" "$out"
@@ -190,6 +195,9 @@ expect "Felis's volumes are retained before their claims go" 'KUBE patch pv pvc-
 refute "a volume of another namespace is not touched" "patch pv pvc-9" "$calls"
 expect "Felis's namespaces are deleted" "KUBE delete namespace felis minecraft felis-build" "$calls"
 expect "the CRD is deleted" "KUBE delete crd minecraftservers.felis.lolicon.best" "$calls"
+[ -f "$root/h/units/k3s.service.d/50-felis.conf" ] \
+  && echo "PASS a k3s that stays keeps its service environment, like its config" \
+  || { echo "FAIL the kept k3s lost its service drop-in"; fails=$((fails + 1)); }
 
 out="$(fresh_host; run_uninstall down --yes)"
 expect "a k3s that does not answer stops the run" "k3s does not answer" "$out"
@@ -198,6 +206,18 @@ run_uninstall down --yes --keep-k3s >/dev/null
 calls="$(cat "$root/calls")"
 refute "--keep-k3s never runs k3s's uninstaller" "RUN k3s-uninstall.sh" "$calls"
 
+# --- k3s already gone ----------------------------------------------------------------------
+fresh_host
+rm -f "$root/h/bin/k3s"
+printf '[Service]\nLimitNOFILE=4096\n' > "$root/h/units/k3s.service.d/90-admin.conf"
+run_uninstall down --yes >/dev/null
+[ ! -e "$root/h/units/k3s.service.d/50-felis.conf" ] \
+  && echo "PASS a k3s removed some other way does not leave the installer's service environment" \
+  || { echo "FAIL the k3s service drop-in outlived k3s"; fails=$((fails + 1)); }
+[ -f "$root/h/units/k3s.service.d/90-admin.conf" ] \
+  && echo "PASS a drop-in someone else wrote beside it stays, with the directory" \
+  || { echo "FAIL the uninstall removed a k3s drop-in it did not write"; fails=$((fails + 1)); }
+
 # --- purge -------------------------------------------------------------------------------
 fresh_host
 out="$(run_uninstall "default felis minecraft" --purge --yes)"