linux-kernel - Re: [Patch 5/8] ia64: implement crashkernel=auto

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Date:	Mon, 24 Aug 2009 09:59:29 +0800
From:	Amerigo Wang <amwang@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	linux-kernel@...r.kernel.org, tony.luck@...el.com,
	linux-ia64@...r.kernel.org, nhorman@...hat.com,
	ebiederm@...ssion.com, andi@...stfloor.org, mingo@...e.hu,
	bernhard.walle@....de, fenghua.yu@...el.com,
	kamezawa.hiroyu@...fujitsu.com, avorontsov@...mvista.com
Subject: Re: [Patch 5/8] ia64: implement crashkernel=auto

Andrew Morton wrote:
> On Fri, 21 Aug 2009 02:55:04 -0400
> Amerigo Wang <amwang@...hat.com> wrote:
>
>   
>> +#ifdef CONFIG_KEXEC_AUTO_RESERVE
>> +#define ARCH_HAS_DEFAULT_CRASH_SIZE
>> +static inline
>> +unsigned long long arch_default_crash_size(unsigned long long total_size)
>> +{
>> +	if (total_size >= 4ULL<<30 && total_size < 12ULL<<30)
>> +		return 1ULL<<28;
>> +	else if (total_size >= 12ULL<<30 && total_size < 128ULL<<30)
>> +		return 1ULL<<29;
>> +	else if (total_size >= 128ULL<<30 && total_size < 256ULL<<30)
>> +		return 3ULL<<28;
>> +	else if (total_size >= 256ULL<<30 && total_size < 378ULL<<30)
>> +		return 1ULL<<30;
>> +	else if (total_size >= 318ULL<<30 && total_size < 512ULL<<30)
>> +		return 3ULL<<29;
>> +	else if (total_size >= 512ULL<<30 && total_size < 768ULL<<30)
>> +		return 2ULL<<30;
>> +	else if (total_size >= 768ULL<<30)
>> +		return 3ULL<<30;
>> +}
>> +#include <asm-generic/kexec.h>
>> +#endif
>>     
>
> a) Why on earth is this inlined?
>
> b) Please consider making arch_default_crash_size() a __weak
>    function.  You'll probably find the result to be pleasing.
>   

Good idea!

> c) If we can't use __weak then please don't add
>    ARCH_HAS_DEFAULT_CRASH_SIZE.  Instead do this trick:
>
>
> 	#ifndef arch_default_crash_size
> 	static inline unsigned long long arch_default_crash_size(unsigned long long total_size)
> 	{
> 		...
> 	}
> 	#define arch_default_crash_size arch_default_crash_size
> 	#endif
>
> 	because i) it's good to standardise on something and ii) one less
> 	symbol gets added to the kernel.
>   

Yes, agree. I will try b) which seems to be better than c).

> d) why is asm-generic/kexec.h only included in asm/kexec.h if
>    CONFIG_KEXEC_AUTO_RESERVE happened to be defined?  That makes no
>    sense - there may be a multitude of reasons why asm/kexec.h wants
>    to include asm-generic/kexec.h.
>
>   
Hmm, yes? kernel/kexec.c includes linux/kexec.h which already includes 
asm/kexec.h....



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