KAMEZAWA Hiroyuki wrote:

On Tue, 18 Aug 2009 14:31:23 +0800
Amerigo Wang [off-list ref] wrote:
  

quoted

Hi, thank you!
    

quoted

Can I have a question ?

  - How crash kernel's memory is preserved at boot ?
  
      

Use bootmem, I think.

    

I see.

In x86,
 
  setup_arch()
	-> reserve_crashkernel()
		-> find_and_reserve_crashkernel()
			-> reserve_bootmem_generic()

Then, all "active range" is already registered and there are memmap.


  

quoted

quoted

    It's hidden from the system before mem_init() ?
  
      

Not sure, but probably yes. It is reserved in setup_arch() which is 
before mm_init() which calls mem_init().

Do you have any advice to free that reserved memory after boot? :)

    

Let's see arch/x86/mm/init.c::free_initmem()

Maybe it's all you want.

	- ClearPageReserved()
	- init_page_count()
	- free_page()
	- totalram_pages++

But it has no argumetns. Maybe you need your own function or modification.
online_pages() does very similar. But, hmm,.. writing something open coded one
for crashkernel is not very bad, I think.
  

Nice help!

Yeah, I think we can make that be a generic wrapper function so that 
both free_initmem() and shrink_crash_memory() can use it.

Then I will update and resend the whole patchset.

Thank you!



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