[PATCH v2] kdumpctl: Add kdumpctl estimate - kexec - Fedora mailing-lists

11 Mar 2021

Add a rough esitimation support, currently, following memory usage are
checked by this sub command:
- System RAM
- Kdump Initramfs size
- Kdump Kernel image size
- Kdump Kernel module size
- Kdump userspace user and other runtime allocated memory (currently
  simply using a fixed value: 64M)
This will provide user three values as reference,
The output of kdumpctl estimate looks like this:
# kdumpctl estimate
    Reserved crashkernel:    128M
    Estimated crashkernel:   143M
    Recommanded crashkernel: 160M
Kernel image size:   47M
    Kernel modules size: 9M
    Initramfs size:      22M
    Runtime reservation: 64M
Large modules:
        nouveau: 2281472
        xfs: 1515520
WARNING: Current crashkernel size is lower than recommanded size 160M.
"Reserved crashkernel" is currently reserved crashkernel value.
"Baseline crashkernel" is the crashkernel size when `crashkernel=auto`
    is used, based on crashkernel auto rules from RHEL.
"Estimated crashkernel" is the estimate value based on the memory usage
    items listed above.
"Recommanded crashkernel" will use the largest value of estimated
crashkernel and the baseline crashkernel.
All values are rounded up and converted to MB.
All modules with static size larger than 1M will be listed as large
module.
Signed-off-by: Kairui Song kasong@redhat.com
---
Update from v1:
  - Fix typos
  - Remove "Baseline crashkernel:" from output
---
 kdump-lib.sh | 67 +++++++++++++++++++++++++++++++++++++++
 kdumpctl     | 88 ++++++++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 153 insertions(+), 2 deletions(-)

diff --git a/kdump-lib.sh b/kdump-lib.sh
index 21271cf..d56622a 100755
--- a/kdump-lib.sh
+++ b/kdump-lib.sh
@@ -900,3 +900,70 @@ kdump_get_arch_recommend_size()
     echo $result
     return 0
 }
+
+check_vmlinux()
+{
+    # Use readelf to check if it's a valid ELF
+    readelf -h $1 &>/dev/null || return 1
+}
+
+get_vmlinux_size()
+{
+    local size=0
+
+    while read _type _offset _virtaddr _physaddr _fsize _msize _flg _aln; do
+        size=$(( $size + $_msize ))
+    done <<< $(readelf -l -W $1 | grep "^  LOAD" 2>/dev/stderr)
+
+    echo $size
+}
+
+try_decompress()
+{
+    # The obscure use of the "tr" filter is to work around older versions of
+    # "grep" that report the byte offset of the line instead of the pattern.
+
+    # Try to find the header ($1) and decompress from here
+    for pos in `tr "$1\n$2" "\n$2=" < "$4" | grep -abo "^$2"`
+    do
+        if ! type -P $3 > /dev/null; then
+            ddebug "Signiature detected but '$3' is missing, skip this decompressor"
+            break
+        fi
+
+        pos=${pos%%:*}
+        tail -c+$pos "$img" | $3 > $5 2> /dev/null
+        if check_vmlinux $5; then
+            ddebug "Kernel is extracted with '$3'"
+            return 0
+        fi
+    done
+
+    return 1
+}
+
+# Borrowed from linux/scripts/extract-vmlinux
+get_kernel_size()
+{
+    # Prepare temp files:
+    local img=$1 tmp=$(mktemp /tmp/vmlinux-XXX)
+    trap "rm -f $tmp" 0
+
+    # Try to check if it's a vmlinux already
+    check_vmlinux $img && get_vmlinux_size $img && return 0
+
+    # That didn't work, so retry after decompression.
+    try_decompress '\037\213\010' xy    gunzip    $img $tmp || \
+    try_decompress '\3757zXZ\000' abcde unxz      $img $tmp || \
+    try_decompress 'BZh'          xy    bunzip2   $img $tmp || \
+    try_decompress '\135\0\0\0'   xxx   unlzma    $img $tmp || \
+    try_decompress '\211\114\132' xy    'lzop -d' $img $tmp || \
+    try_decompress '\002!L\030'   xxx   'lz4 -d'  $img $tmp || \
+    try_decompress '(\265/\375'   xxx   unzstd    $img $tmp
+
+    # Finally check for uncompressed images or objects:
+    get_vmlinux_size $tmp && return 0
+
+    derror "Failed to get kernel image size"
+    return 1
+}
diff --git a/kdumpctl b/kdumpctl
index c3311ad..4109539 100755
--- a/kdumpctl
+++ b/kdumpctl
@@ -1246,6 +1246,87 @@ rebuild() {
    return $?
 }
+do_estimate() {
+	local kdump_mods
+	local -A large_mods
+	local baseline
+	local kernel_size mod_size initrd_size baseline_size runtime_size reserved_size estimated_size recommanded_size
+	local size_mb=$(( 1024 * 1024 ))
+
+	setup_initrd
+
+	if [ ! -f $TARGET_INITRD ]; then
+		derror "kdumpctl estimate: kdump initramfs is not built yet."
+		exit 1
+	fi
+
+	kdump_mods="$(lsinitrd $TARGET_INITRD -f /usr/lib/dracut/hostonly-kernel-modules.txt | tr '\n' ' ')"
+
+	baseline=$(kdump_get_arch_recommend_size)
+	if [[ "${baseline: -1}" == "M" ]]; then
+		baseline=${baseline%M}
+	elif [[ "${baseline: -1}" == "G" ]]; then
+		baseline=$(( ${baseline%G} * 1024 ))
+	elif [[ "${baseline: -1}" == "T" ]]; then
+		baseline=$(( ${baseline%Y} * 1048576 ))
+	fi
+
+	# The default value when using crashkernel=auto
+	baseline_size=$(( $baseline * $size_mb ))
+	# Current reserved crashkernel size
+	reserved_size=$(cat /sys/kernel/kexec_crash_size)
+	# A pre-estimated value for userspace usage and kernel
+	# runtime allocation, 64M should good for most cases
+	runtime_size=$(( 64 * $size_mb ))
+	# Kernel image size
+	kernel_size=$(get_kernel_size $KDUMP_KERNEL)
+	# Kdump initramfs size
+	initrd_size=$(du -b $TARGET_INITRD | awk '{print $1}')
+	# Kernel modules size after loaded
+	mod_size=0
+	while read -r _name _size _; do
+		if [[ ! " $kdump_mods " == *" $_name "* ]]; then
+			continue
+		fi
+		mod_size=$(( $mod_size + $_size ))
+
+		# Mark module with static size larger than 2M as large module
+		if [[ $(( $_size / $size_mb )) -ge 1 ]]; then
+			large_mods[$_name]=$_size
+		fi
+	done <<< "$(< /proc/modules)"
+
+	estimated_size=$(( $kernel_size + $mod_size + $initrd_size + $runtime_size ))
+
+	if [[ $baseline_size -gt $estimated_size ]]; then
+		recommanded_size=$baseline_size
+	else
+		recommanded_size=$estimated_size
+	fi
+
+	echo "Reserved crashkernel:    $(( ( $reserved_size + $size_mb - 1 ) / $size_mb ))M"
+	echo "Estimated crashkernel:   $(( ( $estimated_size + $size_mb - 1 ) / $size_mb ))M"
+	echo "Recommanded crashkernel: $(( ( $recommanded_size + $size_mb - 1 ) / $size_mb ))M"
+	echo
+	echo "Kernel image size:   $(( ( $kernel_size + $size_mb - 1 ) / $size_mb ))M"
+	echo "Kernel modules size: $(( ( $mod_size + $size_mb - 1 ) / $size_mb ))M"
+	echo "Initramfs size:      $(( ( $initrd_size + $size_mb - 1 ) / $size_mb ))M"
+	echo "Runtime reservation: $(( ( $runtime_size + $size_mb - 1 ) / $size_mb ))M"
+	echo -n "Large modules:"
+	if [[ "${#large_mods[@]}" -eq 0 ]]; then
+		echo " <none>"
+	else
+		echo ""
+		for _mod in "${!large_mods[@]}"; do
+			echo "    $_mod: ${large_mods[$_mod]}"
+		done
+	fi
+
+	if [[ $reserved_size -le $recommanded_size ]]; then
+		echo "WARNING: Current crashkernel size is lower than recommanded size $(( ( $recommanded_size + 1023 ) / $size_mb ))M."
+	fi
+}
+
 if [ ! -f "$KDUMP_CONFIG_FILE" ]; then
    derror "Error: No kdump config file found!"
    exit 1
@@ -1301,8 +1382,11 @@ main ()
      showmem)
    	show_reserved_mem
    	;;
+	  estimate)
+		do_estimate $2
+		;;
      *)
-		dinfo $"Usage: $0 {start|stop|status|restart|reload|rebuild|propagate|showmem}"
+		dinfo $"Usage: $0 {start|stop|status|restart|reload|rebuild|propagate|showmem|estimate}"
    	exit 1
    esac
 }
@@ -1312,6 +1396,6 @@ single_instance_lock
# To avoid fd 9 leaking, we invoke a subshell, close fd 9 and call main.
 # So that fd isn't leaking when main is invoking a subshell.
-(exec 9<&-; main $1)
+(exec 9<&-; main $@)
exit $?
-- 
2.29.2

    