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

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Message-ID: <20090824082148.GA16457@mail1.bwalle.de>
Date:	Mon, 24 Aug 2009 10:21:49 +0200
From:	Bernhard Walle <bernhard.walle@....de>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Amerigo Wang <amwang@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, tony.luck@...el.com,
	linux-ia64@...r.kernel.org, nhorman@...hat.com,
	ebiederm@...ssion.com, andi@...stfloor.org, fenghua.yu@...el.com,
	kamezawa.hiroyu@...fujitsu.com, avorontsov@...mvista.com
Subject: Re: [Patch 5/8] ia64: implement crashkernel=auto

* Ingo Molnar <mingo@...e.hu> [2009-08-24 09:43]:
> * Amerigo Wang <amwang@...hat.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
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