[RFC PATCH 3/4] kdump.conf: Introduce "calc_kdump_cpus=<0 | 1>" option

[Xunlei Pang]

Users may want to specify their own "nr_cpus{maxcpus}=X",
in order not to cause conflicts, we need a way to explicitly
activate the nr_cpus automatic calculation. Default is off.

After the number of kdump cpus was determined, we also modify
"/etc/sysconfig/kdump" to announce the change.

Leave the implementation of calculate_kdump_cpus() to the
following patch.

Signed-off-by: Xunlei Pang <xlpang(a)redhat.com&gt;
---
 kdump.conf |  7 +++++++
 kdumpctl   | 41 ++++++++++++++++++++++++++++++++++++++---
 2 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/kdump.conf b/kdump.conf
index ebf9587..f170339 100644
--- a/kdump.conf
+++ b/kdump.conf
@@ -133,6 +133,12 @@
 #             fence_kdump notifications to (this option is mandatory to
 #             enable fence_kdump).
 #
+# calc_kdump_cpus <0 | 1>
+#           - By default, kdump will boot with the number of cpus specified
+#             in "/etc/sysconfig/kdump" which is only one cpu by default.
+#             Specify 1 to let kexec-tools intelligently caculate the number
+#             of cpus for kdump kernel to boot with.
+#
 
 #raw /dev/vg/lv_kdump
 #ext4 /dev/vg/lv_kdump
@@ -153,3 +159,4 @@ core_collector makedumpfile -l --message-level 1 -d 31
 #dracut_args --omit-drivers "cfg80211 snd" --add-drivers "ext2 ext3"
 #fence_kdump_args -p 7410 -f auto -c 0 -i 10
 #fence_kdump_nodes node1 node2
+#calc_kdump_cpus 1
diff --git a/kdumpctl b/kdumpctl
index ce71138..9cd785a 100755
--- a/kdumpctl
+++ b/kdumpctl
@@ -5,6 +5,7 @@ KDUMP_KERNELVER=""
 KDUMP_COMMANDLINE=""
 KEXEC_ARGS=""
 KDUMP_CONFIG_FILE="/etc/kdump.conf"
+KDUMP_SYSCONFIG_FILE="/etc/sysconfig/kdump"
 MKDUMPRD="/sbin/mkdumprd -f"
 SAVE_PATH=/var/crash
 SSH_KEY_LOCATION="/root/.ssh/kdump_id_rsa"
@@ -54,10 +55,44 @@ determine_dump_mode()
 	fi
 }
 
+calculate_kdump_cpus()
+{
+	echo -n "1"
+}
+
+# Automatically choose the number of cpus used by kdump kernel,
+# and replace the old one in $KDUMP_COMMANDLINE_APPEND with it.
+determine_kdump_cpus()
+{
+	local _calc_needed calc_needed=0
+	local cpus
+
+	# No reserved memory case, simply return.
+	if [ "$(get_reserved_memory_mb)" -eq 0 ]; then
+		return
+	fi
+
+	_calc_needed=$(grep ^calc_kdump_cpus $KDUMP_CONFIG_FILE 2>/dev/null)
+	if [ $? -eq 0 ]; then
+		calc_needed=$(echo $_calc_needed | cut -d' '  -f2)
+	fi
+
+	if [ "$calc_needed" = 0 ]; then
+		return
+	fi
+
+	# We need to calculate the number of cpus for kdump kernel, and
+	# replace "nr_cpus{maxcpus}=X" with our caculated result.
+	cpus=$(calculate_kdump_cpus)
+	sed -i $KDUMP_SYSCONFIG_FILE -e "s/nr_cpus=[0-9]*/nr_cpus=$cpus/g"
+	sed -i $KDUMP_SYSCONFIG_FILE -e "s/maxcpus=[0-9]*/maxcpus=$cpus/g"
+}
+
 determine_kdump_sysconfig()
 {
-	if [ -f /etc/sysconfig/kdump ]; then
-		. /etc/sysconfig/kdump
+	if [ -f "$KDUMP_SYSCONFIG_FILE" ]; then
+		determine_kdump_cpus
+		. $KDUMP_SYSCONFIG_FILE
 	fi
 }
 
@@ -287,7 +322,7 @@ check_config()
 		case "$config_opt" in
 		\#* | "")
 			;;
-		raw|ext2|ext3|ext4|minix|btrfs|xfs|nfs|ssh|sshkey|path|core_collector|kdump_post|kdump_pre|extra_bins|extra_modules|default|force_rebuild|dracut_args|fence_kdump_args|fence_kdump_nodes)
+		raw|ext2|ext3|ext4|minix|btrfs|xfs|nfs|ssh|sshkey|path|core_collector|kdump_post|kdump_pre|extra_bins|extra_modules|default|force_rebuild|dracut_args|fence_kdump_args|fence_kdump_nodes|calc_kdump_cpus)
 			[ -z "$config_val" ] && {
 				echo "Invalid kdump config value for option $config_opt."
 				return 1;
-- 
1.8.3.1