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SubjectRe: [Patch 0/8] V5 Implement crashkernel=auto
Michael Ellerman wrote:
> On Wed, 2009-08-26 at 23:15 -0400, Amerigo Wang wrote:
>> V4 -> V5:
>> - Rename the global functions, as suggested by Andrew.
>> - Save some macros, as suggested by Andrew.
>> - Change the high threshold, from 32G to 4G.
>> - Change the low threshold on ppc, suggested by ppc developers.
>> - Make the mm part as a seperate function, suggest by Eric.
>> - Make the IA64 code more readable.
>> - Reorder the patchset again, since review from mm people is done.
>> V3 -> V4:
>> - Reorder the patches.
>> - Really free the reserved memory, instead of remapping it.
>> (Thanks to KAMEZAWA Hiroyuki!)
>> - Release the reserved memory resource when the size is 0.
>> - Use strict_strtoul() instead of simple_strtoul().
>> V2 -> V3:
>> - Use more clever way to calculate reserved memory size, especially for IA64.
>> - Add that patch that implements shrinking reserved memory
>> V1 -> V2:
>> - Use include/asm-generic/kexec.h, suggested by Neil.
>> - Rename a local variable, suggested by Fenghua.
>> - Fix some style problems found by
>> - Unify the Kconfig docs.
>> This series of patch implements automatically reserved memory for crashkernel,
>> by introducing a new boot option "crashkernel=auto". This idea is from Neil.
>> In case of breaking user-space applications, it modifies this boot option after
>> it decides how much memory should be reserved.
>> On different arch, the threshold and reserved memory size is different. Please
>> refer patch 7/8 which contains an update for the documentation.
>> Patch 8/8 implements shrinking reserved memory at run-time, which is useful
>> when more than enough memory is reserved automatically.
>> This patchset _is_ already tested on x86_64, IA64 and ppc64.
> I don't want to sound like a micro-kernel zealot, I'm not, but I'm still
> unconvinced as to why the auto logic needs to go in the kernel. What is
> the compelling reason that the kernel needs to do this calculation vs
> some userspace tool? We already have the syntax that allows defining a
> different crash size depending on the size of RAM.

Take a look at the x86 part, it can not be done _directly_ in kernel
command line with the syntax.

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