This is a rework of the crashkernel=auto patches back to 2009 although I'm not sure if below is the last version of the old effort: https://lkml.org/lkml/2009/8/12/61 https://lwn.net/Articles/345344/ I changed the original design, instead of adding the auto reserve logic in code, in this patch just introduce two kernel config options for the default crashkernel value in MB and the threshold of system memory in MB so that only reserve default when system memory is equal or above the threshold. With the kernel configs distributions can easily change the default values so that people do not need to manually set kernel cmdline for common use cases and one can still overwrite the default value with manual setup or disable it by using crashkernel=0 Signed-off-by: Dave Young <dyoung@xxxxxxxxxx> --- Another difference is with original design the crashkernel size scales with system memory, according to test, large machine may need more memory in kdump kernel because of several factors: 1. cpu numbers, because of the percpu memory allocated for cpus. (kdump can use nr_cpus=1 to workaround this, but some arches do not support nr_cpus=X for example powerpc) 2. IO devices, large system can have a lot of io devices, although we can try to only add those device drivers we needed, it is still a problem because of some built-in drivers, some stacked logical devices eg. device mapper devices, acpi etc. Even if only considering the meta data for driver model it will still be a big number eg. sysfs files etc. 3. The minimum memory requirement for some device drivers are big, even if some of them have implemented low meory profile. It is usual to see 10M memory use for a storage driver. 4. user space initramfs size growing. Busybox is not usable if we need to add udev support and some complicate storage support. Use dracut with systemd, especially networking stuff need more memory. So probably add another kernel config option to scale the memory size eg. CRASHKERNEL_DEFAULT_SCALE_RATIO is also good to have, in RHEL we use base_value + system_mem >> (2^14) for x86. I'm still hesatating how to describe and add this option. Any suggestions will be appreciated. arch/Kconfig | 16 ++++++++++++++++ kernel/crash_core.c | 23 ++++++++++++++++++++++- 2 files changed, 38 insertions(+), 1 deletion(-) --- linux-x86.orig/arch/Kconfig +++ linux-x86/arch/Kconfig @@ -10,6 +10,22 @@ config KEXEC_CORE select CRASH_CORE bool +config CRASHKERNEL_DEFAULT_THRESHOLD_MB + int "System memory size threshold for kdump memory default reserving" + depends on CRASH_CORE + default 0 + help + CRASHKERNEL_DEFAULT_MB is used as default crashkernel value if + the system memory size is equal or bigger than the threshold. + +config CRASHKERNEL_DEFAULT_MB + int "Default crashkernel memory size reserved for kdump" + depends on CRASH_CORE + default 0 + help + This is used as the default kdump reserved memory size in MB. + crashkernel=X kernel cmdline can overwrite this value. + config HAVE_IMA_KEXEC bool --- linux-x86.orig/kernel/crash_core.c +++ linux-x86/kernel/crash_core.c @@ -9,6 +9,7 @@ #include <linux/crash_core.h> #include <linux/utsname.h> #include <linux/vmalloc.h> +#include <linux/sizes.h> #include <asm/page.h> #include <asm/sections.h> @@ -143,6 +144,24 @@ static int __init parse_crashkernel_simp return 0; } +static int __init get_crashkernel_default(unsigned long long system_ram, + unsigned long long *size) +{ + unsigned long long sz = CONFIG_CRASHKERNEL_DEFAULT_MB; + unsigned long long thres = CONFIG_CRASHKERNEL_DEFAULT_THRESHOLD_MB; + + thres *= SZ_1M; + sz *= SZ_1M; + + if (sz >= system_ram || system_ram < thres) { + pr_debug("crashkernel default size can not be used.\n"); + return -EINVAL; + } + *size = sz; + + return 0; +} + #define SUFFIX_HIGH 0 #define SUFFIX_LOW 1 #define SUFFIX_NULL 2 @@ -240,8 +259,10 @@ static int __init __parse_crashkernel(ch *crash_size = 0; *crash_base = 0; - ck_cmdline = get_last_crashkernel(cmdline, name, suffix); + if (!strstr(cmdline, "crashkernel=")) + return get_crashkernel_default(system_ram, crash_size); + ck_cmdline = get_last_crashkernel(cmdline, name, suffix); if (!ck_cmdline) return -EINVAL; _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
