[PATCH v3 1/1] kernel/crash_core: Add crashkernel=auto for vmcore creation

[john.p.donnelly at oracle.com]

On 2/17/21 8:02 PM, Baoquan He wrote:
> On 02/11/21 at 10:08am, 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 at oracle.com>
>> Signed-off-by: John Donnelly <john.p.donnelly at oracle.com>
>> Tested-by: John Donnelly <john.p.donnelly at oracle.com>
>> ---
>>   Documentation/admin-guide/kdump/kdump.rst     |  3 ++-
>>   .../admin-guide/kernel-parameters.txt         |  6 +++++
>>   arch/Kconfig                                  | 24 +++++++++++++++++++
>>   kernel/crash_core.c                           |  7 ++++++
>>   4 files changed, 39 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
>> index 2da65fef2a1c..e55cdc404c6b 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 7d4e523646c3..aa2099465458 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -736,6 +736,12 @@
>>   			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 af14a567b493..f87c88ffa2f8 100644
>> --- a/arch/Kconfig
>> +++ b/arch/Kconfig
>> @@ -14,6 +14,30 @@ menu "General architecture-dependent options"
>>   config CRASH_CORE
>>   	bool
>>   
>> +if CRASH_CORE
>> +
>> +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
>> +
>> +endif # CRASH_CORE
> 
> Wondering if this CRASH_CORE ifdeffery is a little redundent here
> since CRASH_CORE dependency has been added. Except of this, I like this
> patch. As we discussed in private threads, we can try to push it into
> mainline and continue improving later.

Hi,

Are we good to move forward with this and apply it now?

Dave Young acked it.

Thank you,

John.

(Note - I am currently not on any vger.kernel.org dlist at the moment so 
please cc me ).



> 
> 
>> +
>>   config KEXEC_CORE
>>   	select CRASH_CORE
>>   	bool
>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
>> index 106e4500fd53..ab0a2b4b1ffa 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
>>
>