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Date: Mon, 24 Aug 2009 10:21:49 +0200
From: Bernhard Walle <bernhard.walle@gmx.de>
To: Ingo Molnar <mingo@elte.hu>
Cc: Amerigo Wang <amwang@redhat.com>,
       Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org,
       tony.luck@intel.com, linux-ia64@vger.kernel.org, nhorman@redhat.com,
       ebiederm@xmission.com, andi@firstfloor.org, fenghua.yu@intel.com,
       kamezawa.hiroyu@jp.fujitsu.com, avorontsov@ru.mvista.com
Subject: Re: [Patch 5/8] ia64: implement crashkernel=auto
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* Ingo Molnar <mingo@elte.hu> [2009-08-24 09:43]:
> * Amerigo Wang <amwang@redhat.com> wrote:
> >
> > The reason that I kept 2ULL<<30 instead of 1ULL<<31 is that '1<<30' is  
> > exactly 1G, so 2ULL<<30 can be easily read as 2G. ;)
> 
> i have no trouble reading 1ULL<<31 as 2G ;-) OTOH, the logic and 
> pattern of the comparisons (especially without the comment) looked 
> odd at first sight, until i noticed this.

Why not just something like

    #define KBYTE(x)  ((x)*1024ULL)
    #define MBYTE(x)  ((x)*1024ULL*1024)
    #define GBYTE(x)  ((x)*1024ULL*1024*1024) 
    #define TBYTE(x)  ((x)*1024ULL*1024*1024*1024)

I find GBYTE(2) much easier to read than 1ULL<<31. Honestly, I would
add a comment '/* 2G */' if I would write 1ULL<<31 in own code.

But I'm of course not one of that super kernel hackers. ;-)


Regards,
Bernhard