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

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Message-ID: <4A97ABA9.8030604@redhat.com>
Date:	Fri, 28 Aug 2009 18:04:25 +0800
From:	Amerigo Wang <amwang@...hat.com>
To:	"Yu, Fenghua" <fenghua.yu@...el.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

Yu, Fenghua wrote:
>>>> +	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?
>   

Oops, in fact it was supposed to be:

  if (ret + base > GBYTES(4))
    //blah blah

Hmm, but is it possible for ia64 to choose a base address above 1G? If 
no, that code can be removed.

Thanks!



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