kdump.service takes a long time to start

[challvy]

Hi, when I installed the latest version of kdump-utils from CentOS Stream 10 (specifically kdump-utils-1.0.58-4.el10) on Red Hat Enterprise Linux 10, the kdump.service takes a very long time to start on every system boot, which can be seen by running systemd-analyze blame | grep -i kdump.

This is clearly visible when running:

$ yum remove kdump-utils.x86_64

$ wget https://mirror.stream.centos.org/10-stream/BaseOS/x86_64/os/Packages/kdump-utils-1.0.58-4.el10.x86_64.rpm

$ rpm -ivh kdump-utils-1.0.58-4.el10.x86_64.rpm 

$ reboot 

$ systemd-analyze blame | grep -i kdump
38.899s kdump.service

$ time systemctl restart kdump.service
real    0m16.528s
user    0m0.004s
sys     0m0.007s

In fact, this issue can also be reproduced on other operating systems in the RHEL 10 series.

---

Through investigation and verification, I’ve identified that this performance regression is caused by a specific patch: kdump-lib-initramfs: rewrite kdump_get_conf_val

After the original regular expression was modified, the code execution efficiency became very low, resulting in long startup times.

The log I obtained by adding set -x at the top of the file /usr/lib/kdump/kdump-lib-initramfs.sh is as follows:

kdump.service.log

This is also reported in RHEL-137945

[prudo1]

Hi @challvy,

thanks for reporting. I didn't expect the performance hit to be that bad...

I took a quick look and came up with the patch below. It moves the removal of comments and empty lines back to a regex and should improve the performance drastically. Can you give it a try?

Thanks
Philipp

index 6f5d6db..5214b28 100755
--- a/kdump-lib-initramfs.sh
+++ b/kdump-lib-initramfs.sh
@@ -30,38 +30,40 @@ kdump_get_conf_val()
        _found=""
 
        [ -f "$KDUMP_CONFIG_FILE" ] || return
-       while read -r _line; do
-               _line="$(echo "$_line" | tr -s "[:blank:]" " ")"
-               case "$_line" in
-               "" | \#*)
-                       continue
-                       ;;
-               *\#*)
-                       _line="${_line%%\#*}"
-                       _line="${_line% }"
-                       ;;
-               esac
-
-               _opt=${_line%% *}
-               _val=${_line#* }
-
-               case "$_val" in
-               \"*\")
-                       # Remove quotes
-                       _val="${_val#\"}"
-                       _val="${_val%\"}"
-                       ;;
-               esac
-
-               if [ -z "$_to_find" ]; then
-                       echo "$_opt $_val"
-               elif echo "$_opt" | grep -q -E "^($_to_find)$"; then
-                       # make sure to only return the last match to mirror the
-                       # old behavior
-                       _found="$_val"
-               fi
-       done < "$KDUMP_CONFIG_FILE"
-       [ -n "$_found" ] && echo "$_found"
+
+       # On lines that are _not_ comments or empty
+       # Note: The additional braces {} are required as piping into a while
+       # loop creates a sub-shell. So without the braces $_found would only be
+       # set inside the loop but empty outside of it.
+       grep -Ev -e '^\s*#' -e '^\s*$' "$KDUMP_CONFIG_FILE" | {
+               while read -r _opt _val; do
+                       # remove trailing comments
+                       case "$_val" in
+                       *\#*)
+                               _val="$(echo "$_val" | sed -e "s/\s*#.*//")"
+                               ;;
+                       esac
+
+                       # remove quotes
+                       case "$_val" in
+                       \"*\")
+                               # Remove quotes
+                               _val="${_val#\"}"
+                               _val="${_val%\"}"
+                               ;;
+                       esac
+
+                       if [ -z "$_to_find" ]; then
+                               echo "$_opt $_val"
+                       elif echo "$_opt" | grep -q -E "^($_to_find)$"; then
+                               # make sure to only return the last match to mirror the
+                               # old behavior
+                               _found="$_val"
+                       fi
+               done
+
+               [ -n "$_found" ] && echo "$_found"
+       }
 
        # make sure we return 0 even when a option isn't set
        return 0

[challvy]

@prudo1 Thank you very much for your reply and support!
I've tested this patch, and the results show that it effectively resolves the issue.
Below are my test details:

Test results with the original version

# systemd-analyze blame | grep -i kdump
20.445s kdump.service

# journalctl -u kdump.service -b 0
Jan 08 21:54:43 systemd[1]: Starting kdump.service - Crash recovery kernel arming...
Jan 08 21:55:03 kdumpctl[1756]: kdump: kexec: loaded kdump kernel
Jan 08 21:55:03 kdumpctl[1756]: kdump: Starting kdump: [OK]
Jan 08 21:55:03 systemd[1]: Finished kdump.service - Crash recovery kernel arming.

# systemctl status kdump.service 
● kdump.service - Crash recovery kernel arming
     Loaded: loaded (/usr/lib/systemd/system/kdump.service; enabled; preset: enabled)
     Active: active (exited) since Thu 2026-01-08 21:55:03 CST; 5min ago
 Invocation: 74c52d1a3ff848209eddc810610fcf65
    Process: 1737 ExecStart=/usr/bin/kdumpctl start (code=exited, status=0/SUCCESS)
   Main PID: 1737 (code=exited, status=0/SUCCESS)
   Mem peak: 252.8M
        CPU: 22.328s

Jan 08 21:54:43 systemd[1]: Starting kdump.service - Crash recovery kernel arming...
Jan 08 21:55:03 kdumpctl[1756]: kdump: kexec: loaded kdump kernel
Jan 08 21:55:03 kdumpctl[1756]: kdump: Starting kdump: [OK]
Jan 08 21:55:03 systemd[1]: Finished kdump.service - Crash recovery kernel arming.

Test results with the fixed version

# systemd-analyze blame | grep -i kdump
1.746s kdump.service

# journalctl -u kdump.service -b 0
Jan 08 22:03:41 systemd[1]: Starting kdump.service - Crash recovery kernel arming...
Jan 08 22:03:43 kdumpctl[1193]: kdump: kexec: loaded kdump kernel
Jan 08 22:03:43 kdumpctl[1193]: kdump: Starting kdump: [OK]
Jan 08 22:03:43 systemd[1]: Finished kdump.service - Crash recovery kernel arming.

# systemctl status kdump.service 
● kdump.service - Crash recovery kernel arming
     Loaded: loaded (/usr/lib/systemd/system/kdump.service; enabled; preset: enabled)
     Active: active (exited) since Thu 2026-01-08 22:03:43 CST; 32s ago
 Invocation: def63c8a046545cf97a76b39c3522c30
    Process: 1160 ExecCondition=/bin/sh -c grep -q -e "crashkernel" -e "fadump" /proc/cmdline (code=exited, status=0/SUCCESS)
    Process: 1170 ExecStart=/usr/bin/kdumpctl start (code=exited, status=0/SUCCESS)
   Main PID: 1170 (code=exited, status=0/SUCCESS)
   Mem peak: 252M
        CPU: 1.376s

Jan 08 22:03:41 systemd[1]: Starting kdump.service - Crash recovery kernel arming...
Jan 08 22:03:43 kdumpctl[1193]: kdump: kexec: loaded kdump kernel
Jan 08 22:03:43 kdumpctl[1193]: kdump: Starting kdump: [OK]
Jan 08 22:03:43 systemd[1]: Finished kdump.service - Crash recovery kernel arming.

[prudo1]

Opened #137 to fix the issue