linux-kernel - RE: [Patch 4/8] ia64: implement crashkernel=auto

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Date:	Thu, 27 Aug 2009 11:13:32 -0700
From:	"Yu, Fenghua" <fenghua.yu@...el.com>
To:	'Amerigo Wang' <amwang@...hat.com>
CC:	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
	'Anton Vorontsov' <avorontsov@...mvista.com>,
	"Luck, Tony" <tony.luck@...el.com>,
	"'linux-ia64@...r.kernel.org'" <linux-ia64@...r.kernel.org>,
	'Neil Horman' <nhorman@...hat.com>,
	"'Eric W. Biederman'" <ebiederm@...ssion.com>,
	"'kamezawa.hiroyu@...fujitsu.com'" <kamezawa.hiroyu@...fujitsu.com>,
	'Andi Kleen' <andi@...stfloor.org>,
	'Michael Ellerman' <michael@...erman.id.au>,
	"'M. Mohan Kumar'" <mohan@...ibm.com>,
	"'akpm@...ux-foundation.org'" <akpm@...ux-foundation.org>,
	"'bernhard.walle@....de'" <bernhard.walle@....de>,
	'Ingo Molnar' <mingo@...e.hu>
Subject: RE: [Patch 4/8] ia64: implement crashkernel=auto

>>> --- linux-2.6.orig/arch/ia64/include/asm/kexec.h
>>> +++ linux-2.6/arch/ia64/include/asm/kexec.h
>>> @@ -1,6 +1,7 @@
>>> #ifndef _ASM_IA64_KEXEC_H
>>> #define _ASM_IA64_KEXEC_H
>>>
>>> +#include <asm-generic/kexec.h>
>>>
>>> /* Maximum physical address we can use pages from */
>>> #define KEXEC_SOURCE_MEMORY_LIMIT (-1UL)
>>> @@ -19,6 +20,49 @@
>>>                 flush_icache_range(page_addr, page_addr + PAGE_SIZE); \
>>>         } while(0)
>>>
>>> +#ifdef CONFIG_KEXEC_AUTO_RESERVE
>>> +#define MBYTES(n) ((n)*1024*1024ULL)
>>> +#define GBYTES(n) ((n)*1024*1024*1024ULL)
>>> +/*
>>> +       Memory size     Reserved memory
>>> +       ===========     ===============
>>> +       [4G, 12G)       256M
>>> +       [12G, 128G)     512M
>>> +       [128G, 256G)    768M
>>> +       [256G, 378G)    1024M
>>> +       [378G, 512G)    1536M
>>> +       [512G, 768G)    2048M
>>> +       [768G, )        3072M
>>> + */
>>> +static inline
>>> +unsigned long long arch_default_crash_size(unsigned long long
>total_size)
>>> +{
>>>
>>
>> This function shouldn't be inlined (Andrew commented this before). You
>might remove inline and add __init for this function.
>>
>>
>
>Yeah, seems I missed Andrew's comment... :-/ I will update it.
>
>>> +	unsigned long long ret;
>>> +
>>> +	if (total_size >= GBYTES(4) && total_size < GBYTES(12))
>>> +		ret = MBYTES(256);
>>> +	else if (total_size >= GBYTES(12) && total_size < GBYTES(128))
>>> +		ret = MBYTES(512);
>>> +	else if (total_size >= GBYTES(128) && total_size < GBYTES(256))
>>> +		ret = MBYTES(768);
>>> +	else if (total_size >= GBYTES(256) && total_size < GBYTES(378))
>>> +		ret = MBYTES(1024);
>>> +	else if (total_size >= GBYTES(318) && total_size < GBYTES(512))
>>> +		ret = MBYTES(1536);
>>> +	else if (total_size >= GBYTES(512) && total_size < GBYTES(768))
>>> +		ret = MBYTES(2048);
>>> +	else
>>> +		ret = MBYTES(3072);
>>> +	if (!ia64_platform_is("sn2") && !ia64_platform_is("uv"))
>>> +		if (ret > GBYTES(4))
>>> +			ret = ret / GBYTES(4) * MBYTES(256);
>>>
>>
>> This code doesn't make sense to me. What you really want is following
>code, right?
>> +		if (total_size > GBYTES(4))
>> +			ret = total_size / GBYTES(4) * MBYTEST(256)
>>
>>
>Nope. Check check_crashkernel_memory().

This statement will be ALWAYS false:
+		if (ret > GBYTES(4))
since ret's max value is 3GB after the above total_size checks.

So the code doesn't make sense. Did I miss something?

Thanks.

-Fenghua
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