[PATCH v2 09/11] reduce kdump memory consumption by only installing needed NIC drivers

[Coiby Xu]

Even after having asked NM to stop managing a unneeded NIC, a NIC driver
may still waste memory. For example, mlx5_core uses a substantial amount
of memory during driver initialization,

======== Report format module_summary: ========
Module mlx5_core using 350.2MB (89650 pages), peak allocation 367.4MB (94056 pages)
Module squashfs using 13.1MB (3360 pages), peak allocation 13.1MB (3360 pages)
Module overlay using 2.1MB (550 pages), peak allocation 2.2MB (555 pages)
Module dns_resolver using 0.9MB (219 pages), peak allocation 5.2MB (1338 pages)
Module mlxfw using 0.7MB (172 pages), peak allocation 5.3MB (1349 pages)
======== Report format module_summary END ========

======== Report format module_top: ========
Top stack usage of module mlx5_core:
  (null) Pages: 89650 (peak: 94056)
    ret_from_fork (0xffffda088b4165f8) Pages: 60007 (peak: 60007)
      kthread (0xffffda088b4bd7e4) Pages: 60007 (peak: 60007)
        worker_thread (0xffffda088b4b48d0) Pages: 60007 (peak: 60007)
          process_one_work (0xffffda088b4b3f40) Pages: 60007 (peak: 60007)
            work_for_cpu_fn (0xffffda088b4aef00) Pages: 53906 (peak: 53906)
              local_pci_probe (0xffffda088b9e1e44) Pages: 53906 (peak: 53906)
                probe_one mlx5_core (0xffffda084f899cc8) Pages: 53518 (peak: 53518)
                  mlx5_init_one mlx5_core (0xffffda084f8994ac) Pages: 49756 (peak: 49756)
                    mlx5_function_setup.constprop.0 mlx5_core (0xffffda084f899100) Pages:
44434 (eak: 44434)
                      mlx5_satisfy_startup_pages mlx5_core (0xffffda084f8a4f24) Pages:
44434 (peak: 44434)
                    mlx5_function_setup.constprop.0 mlx5_core (0xffffda084f899078) Pages:
5285 (peak: 5285)
                      mlx5_cmd_init mlx5_core (0xffffda084f89e414) Pages: 4818 (peak:
4818)
                        mlx5_alloc_cmd_msg mlx5_core (0xffffda084f89aaa0) Pages: 4403
(peak: 4403)

This memory consumption is completely unnecessary when kdump doesn't need
this NIC. Only install needed NIC drivers to prevent this kind of waste.

Note
1. this patch depends on [1] to ask dracut to not install NIC drivers.
2. "ethtool -i" somehow fails to get the vlan driver
3. team.ko doesn't depend on the team mode drivers so we need to install
   the team mode drivers manually.

[1] https://github.com/dracutdevs/dracut/pull/1789

Signed-off-by: Coiby Xu <coxu(a)redhat.com&gt;
---
 dracut-module-setup.sh | 31 +++++++++++++++++++++++++++++++
 mkdumprd               |  2 +-
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/dracut-module-setup.sh b/dracut-module-setup.sh
index f861d3b..01df7b7 100755
--- a/dracut-module-setup.sh
+++ b/dracut-module-setup.sh
@@ -328,6 +328,36 @@ kdump_install_nm_netif_allowlist() {
     inst "$_netif_allowlist_nm_conf"
"/etc/NetworkManager/conf.d/10-kdump-netif.conf"
 }
 
+_get_nic_driver() {
+    ethtool -i "$1" | sed -n -E "s/driver: (.*)/\1/p"
+}
+
+kdump_install_nic_driver() {
+    local _netif _driver _drivers
+
+    _drivers=()
+
+    for _netif in $1; do
+        _driver=$(_get_nic_driver "$_netif")
+        if [[ -z $_driver ]]; then
+            derror "Failed to get the driver of $_netif"
+            exit 1
+        fi
+
+        if [[ $_driver == "802.1Q VLAN Support" ]]; then
+            # ethtool somehow doesn't return the driver name for a VLAN NIC
+            _driver=8021q
+        elif [[ $_driver == "team" ]]; then
+            # install the team mode drivers like team_mode_roundrobin.ko as well
+            _driver='=drivers/net/team'
+        fi
+
+        _drivers+=("$_driver")
+    done
+
+    instmods "${_drivers[@]}"
+}
+
 kdump_setup_bridge() {
     local _netdev=$1
     local _dev
@@ -1006,6 +1036,7 @@ install() {
     _netifs=$(cat "$_TMP_KDUMP_NETIFS")
     if [[ -n "$_netifs" ]]; then
         kdump_install_nm_netif_allowlist "$_netifs"
+        kdump_install_nic_driver "$_netifs"
     fi
 
     # For the lvm type target under kdump, in /etc/lvm/lvm.conf we can
diff --git a/mkdumprd b/mkdumprd
index bcbf47b..1a3747b 100644
--- a/mkdumprd
+++ b/mkdumprd
@@ -27,7 +27,7 @@ SAVE_PATH=$(get_save_path)
 OVERRIDE_RESETTABLE=0
 
 extra_modules=""
-dracut_args=(--add kdumpbase --quiet --hostonly --hostonly-cmdline --hostonly-i18n
--hostonly-mode strict -o "plymouth resume ifcfg earlykdump")
+dracut_args=(--add kdumpbase --quiet --hostonly --hostonly-cmdline --hostonly-i18n
--hostonly-mode strict --hostonly-nics '' -o "plymouth resume ifcfg
earlykdump")
 
 MKDUMPRD_TMPDIR="$(mktemp -d -t mkdumprd.XXXXXX)"
 [ -d "$MKDUMPRD_TMPDIR" ] || perror_exit "dracut: mktemp -p -d -t
dracut.XXXXXX failed."
-- 
2.37.1