[finalize-warmboot.sh] reset cpufreq governor to default (sonic-net#1…

…9634)

#### Why I did it

Set cpufreq.default_governor to *performance* for faster boot time. We observe consistent 1 sec improvement across several devices.

The change in finalize-warmboot.sh restores the default governor after fast or warm boot is finished.

**NOTE**: This will apply to upgrades starting from 202405 since this is set in shutdown path to avoid any extra scripts running at boot time. Upgrade from older versions/branches will require a runtime patch to fast-reboot and warm-reboot script.

#### How I did it

After fast or warm boot is finished restore to default governor.

#### How to verify it

Run fast-reboot or warm-reboot. Check:
```
admin@sonic:~$ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
performance
```

After boot is finalized check that it is reset back to default:
```
admin@sonic:~$ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
schedutil
```

Tested with sonic-net/sonic-utilities#3435

files/image_config/warmboot-finalizer/finalize-warmboot.sh

@@ -2,6 +2,9 @@
 
 VERBOSE=no
 
+# read SONiC immutable variables
+[ -f /etc/sonic/sonic-environment ] && . /etc/sonic/sonic-environment
+
 # Define components that needs to reconcile during warm
 # boot:
 #       The key is the name of the service that the components belong to.
@@ -101,16 +104,34 @@ function check_list()
     echo ${RET_LIST}
 }
 
+function set_cpufreq_governor() {
+    local -r governor="$1"
+    echo "$governor" | tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor 1> /dev/null \
+        && debug "Set CPUFreq scaling governor to $governor" \
+        || debug "Failed to set CPUFreq scaling governor to $governor"
+}
+
+function finalize_common() {
+    local -r asic_type=${ASIC_TYPE:-`sonic-cfggen -y /etc/sonic/sonic_version.yml -v asic_type`}
+
+    if [[ "$asic_type" == "mellanox" ]]; then
+        # Read default governor from kernel config
+        local -r default_governor=$(cat "/boot/config-$(uname -r)" | grep -E 'CONFIG_CPU_FREQ_DEFAULT_GOV_.*=y' | sed -E 's/CONFIG_CPU_FREQ_DEFAULT_GOV_(.*)=y/\1/')
+        set_cpufreq_governor "$default_governor"
+    fi
+}
 
 function finalize_warm_boot()
 {
     debug "Finalizing warmboot..."
+    finalize_common
     sudo config warm_restart disable
 }
 
 function finalize_fast_reboot()
 {
     debug "Finalizing fast-reboot..."
+    finalize_common
     sonic-db-cli STATE_DB hset "FAST_RESTART_ENABLE_TABLE|system" "enable" "false" &>/dev/null
     sonic-db-cli CONFIG_DB DEL "WARM_RESTART|teamd" &>/dev/null
 }