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kdump-lib.sh: Adjust default crashkernel reservation for x86_64 and s390x

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Resolves: RHEL-83645
Upstream: kdump-utils

commit fe18f933baed9eaa18e0c2427aaca4640d8f6fa1
Author: Lichen Liu <lichliu@redhat.com>
Date:   Thu Mar 6 10:21:43 2025 +0800

    kdump-lib.sh: Adjust default crashkernel reservation for x86_64 and s390x

    With new kernel features being added, both the kernel itself and the initramfs
    have gradually increased in size.

    Previously, we used squashfs to package and reduce the initramfs size. However,
    since squashfs will be replaced by erofs, we have transitioned to erofs. The
    compression algorithms supported by erofs differ from those used in squashfs.
    In previous squashfs implementations, we used zstd compression, but in RHEL-10,
    the erofs implementation in the kernel does not yet support zstd decompression.
    As a result, we had to switch to other compression algorithms, leading to
    changes in the initramfs size.

    In some scenarios, the previous 192M crashkernel reservation is no longer
    sufficient. Recent NFS testing has shown that at least 238M is required to
    successfully capture a vmcore. Given this, we have updated the default
    crashkernel reservation to start from 2G, with 256M allocated for crash
    recovery.

    Since 256M is a significant portion of memory on smaller systems, we have
    decided not to reserve crashkernel memory by default on systems with less
    than 2G of RAM. However, users can still manually adjust the `crashkernel=`
    setting via tools like `grubby` if needed.

    Signed-off-by: Lichen Liu <lichliu@redhat.com>

Signed-off-by: Lichen Liu <lichliu@redhat.com>
This commit is contained in:
Lichen Liu 2025-04-14 10:29:14 +08:00 committed by Tao Liu
parent 1553eb62da
commit 3053d95923
2 changed files with 3 additions and 3 deletions
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2
crashkernel-howto.txt
View File

@ -17,7 +17,7 @@ Latest kexec-tools provides "kdumpctl get-default-crashkernel" to retrieve
the default crashkernel value,
$ echo $(kdumpctl get-default-crashkernel)
1G-4G:192M,4G-64G:256M,64G-:512M
2G-64G:256M,64G-:512M
It will be taken as the default value of 'crashkernel=', you can use
this value as a reference for setting crashkernel value manually.

4
kdump-lib.sh
View File

@ -1153,13 +1153,13 @@ kdump_get_arch_recommend_crashkernel()
_arch=$(uname -m)
if [[ $_arch == "x86_64" ]] || [[ $_arch == "s390x" ]]; then
_ck_cmdline="1G-4G:192M,4G-64G:256M,64G-:512M"
_ck_cmdline="2G-64G:256M,64G-:512M"
is_sme_or_sev_active && ((_delta += 64))
elif [[ $_arch == "aarch64" ]]; then
local _running_kernel
# Base line for 4K variant kernel. The formula is based on x86 plus extra = 64M
_ck_cmdline="1G-4G:256M,4G-64G:320M,64G-:576M"
_ck_cmdline="2G-4G:256M,4G-64G:320M,64G-:576M"
if [[ -z "$2" ]]; then
_running_kernel=$(_get_kdump_kernel_version)
else