Re: [PATCH v4 1/1] kernel/crash_core: Add crashkernel=auto for vmcore creation

john.p.donnelly
2021-03-03T10:53:47Z

On 2/25/21 6:38 PM, Dave Young wrote:
> On 02/23/21 at 09:41am, Saeed Mirzamohammadi wrote:
>> This adds crashkernel=auto feature to configure reserved memory for
>> vmcore creation. CONFIG_CRASH_AUTO_STR is defined to be set for
>> different kernel distributions and different archs based on their
>> needs.
>>
>> Signed-off-by: Saeed Mirzamohammadi <saeed.mirzamohammadi@oracle.com>
>> Signed-off-by: John Donnelly <john.p.donnelly@oracle.com>
>> Tested-by: John Donnelly <john.p.donnelly@oracle.com>
>> ---
>> Documentation/admin-guide/kdump/kdump.rst | 3 ++-
>> .../admin-guide/kernel-parameters.txt | 6 ++++++
>> arch/Kconfig | 20 +++++++++++++++++++
>> kernel/crash_core.c | 7 +++++++
>> 4 files changed, 35 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
>> index 75a9dd98e76e..ae030111e22a 100644
>> --- a/Documentation/admin-guide/kdump/kdump.rst
>> +++ b/Documentation/admin-guide/kdump/kdump.rst
>> @@ -285,7 +285,8 @@ This would mean:
>> 2) if the RAM size is between 512M and 2G (exclusive), then reserve 64M
>> 3) if the RAM size is larger than 2G, then reserve 128M
>>
>> -
>> +Or you can use crashkernel=auto to choose the crash kernel memory size
>> +based on the recommended configuration set for each arch.
>>
>> Boot into System Kernel
>> =======================
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index 9e3cdb271d06..a5deda5c85fe 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -747,6 +747,12 @@
>> a memory unit (amount[KMG]). See also
>> Documentation/admin-guide/kdump/kdump.rst for an example.
>>
>> + crashkernel=auto
>> + [KNL] This parameter will set the reserved memory for
>> + the crash kernel based on the value of the CRASH_AUTO_STR
>> + that is the best effort estimation for each arch. See also
>> + arch/Kconfig for further details.
>> +
>> crashkernel=size[KMG],high
>> [KNL, X86-64] range could be above 4G. Allow kernel
>> to allocate physical memory region from top, so could
>> diff --git a/arch/Kconfig b/arch/Kconfig
>> index 24862d15f3a3..23d047548772 100644
>> --- a/arch/Kconfig
>> +++ b/arch/Kconfig
>> @@ -14,6 +14,26 @@ menu "General architecture-dependent options"
>> config CRASH_CORE
>> bool
>>
>> +config CRASH_AUTO_STR
>> + string "Memory reserved for crash kernel"
>> + depends on CRASH_CORE
>> + default "1G-64G:128M,64G-1T:256M,1T-:512M"
>> + help
>> + This configures the reserved memory dependent
>> + on the value of System RAM. The syntax is:
>> + crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
>> + range=start-[end]
>> +
>> + For example:
>> + crashkernel=512M-2G:64M,2G-:128M
>> +
>> + This would mean:
>> +
>> + 1) if the RAM is smaller than 512M, then don't reserve anything
>> + (this is the "rescue" case)
>> + 2) if the RAM size is between 512M and 2G (exclusive), then reserve 64M
>> + 3) if the RAM size is larger than 2G, then reserve 128M
>> +
>> config KEXEC_CORE
>> select CRASH_CORE
>> bool
>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
>> index 825284baaf46..90f9e4bb6704 100644
>> --- a/kernel/crash_core.c
>> +++ b/kernel/crash_core.c
>> @@ -7,6 +7,7 @@
>> #include <linux/crash_core.h>
>> #include <linux/utsname.h>
>> #include <linux/vmalloc.h>
>> +#include <linux/kexec.h>
>>
>> #include <asm/page.h>
>> #include <asm/sections.h>
>> @@ -250,6 +251,12 @@ static int __init __parse_crashkernel(char *cmdline,
>> if (suffix)
>> return parse_crashkernel_suffix(ck_cmdline, crash_size,
>> suffix);
>> +#ifdef CONFIG_CRASH_AUTO_STR
>> + if (strncmp(ck_cmdline, "auto", 4) == 0) {
>> + ck_cmdline = CONFIG_CRASH_AUTO_STR;
>> + pr_info("Using crashkernel=auto, the size chosen is a best effort estimation.\n");
>> + }
>> +#endif
>> /*
>> * if the commandline contains a ':', then that's the extended
>> * syntax -- if not, it must be the classic syntax
>> --
>> 2.27.0
>>
>
>
> Acked-by: Dave Young <dyoung@redhat.com>
>
> Thanks
> Dave
>
Hi,

Thank you.

When can we expect this to be applied in a future build ?