[PATCH v2 4/3] kdumpctl: improve "while read" time for /etc/kdump.conf

[Xunlei Pang]

I found using "cat $KDUMP_CONFIG_FILE|grep -v "^#"|while read ..."
instead of "while read ... do ...; done < $KDUMP_CONFIG_FILE" will
make the script run faster.

(in case of no initramfs rebuild)
Before this patchset:
    $ time kdumpctl start
    kexec: loaded kdump kernel
    Starting kdump: [OK]

    real    0m0.854s
    user    0m0.389s
    sys     0m0.582s

After this patchset:
    $ time kdumpctl start
    kexec: loaded kdump kernel
    Starting kdump: [OK]

    real    0m0.465s
    user    0m0.305s
    sys     0m0.194s

Now most of start time is consumed by kexec syscall(around 0.330s)
which is impossible for us to optimize from kdump side.

Signed-off-by: Xunlei Pang <xlpang(a)redhat.com&gt;
---
Please append to "[PATCH v2 0/3] optimize kdump service start time in case of no
initramfs rebuild".

 kdumpctl | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kdumpctl b/kdumpctl
index 11d7f1f..d075a1a 100755
--- a/kdumpctl
+++ b/kdumpctl
@@ -365,7 +365,7 @@ check_config()
 		return 1
 	}
 
-	while read config_opt config_val; do
+	cat $KDUMP_CONFIG_FILE | grep -v "^#" | while read config_opt config_val; do
 		# remove inline comments after the end of a directive.
 		config_val=$(strip_comments $config_val)
 		case "$config_opt" in
@@ -386,7 +386,7 @@ check_config()
 			return 1;
 			;;
 		esac
-	done < $KDUMP_CONFIG_FILE
+	done
 
 	check_default_config || return 1
 
@@ -792,7 +792,7 @@ load_kdump()
 
 check_ssh_config()
 {
-	while read config_opt config_val; do
+	cat $KDUMP_CONFIG_FILE | grep -v "^#" | while read config_opt config_val; do
 		# remove inline comments after the end of a directive.
 		config_val=$(strip_comments $config_val)
 		case "$config_opt" in
@@ -813,7 +813,7 @@ check_ssh_config()
 		*)
 			;;
 		esac
-	done < $KDUMP_CONFIG_FILE
+	done
 
 	#make sure they've configured kdump.conf for ssh dumps
 	local SSH_TARGET=`echo -n $DUMP_TARGET | sed -n '/.*@/p'`
-- 
1.8.3.1