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Message-ID: <443A6789.9090809@sw.ru>
Date: Mon, 10 Apr 2006 18:11:21 +0400
From: Kirill Korotaev <dev@sw.ru>
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To: Sergey Vlasov <vsu@altlinux.ru>
CC: Jens Axboe <axboe@suse.de>, Byron Stanoszek <gandalf@winds.org>,
       Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org,
       Andrew Morton <akpm@osdl.org>, Linus Torvalds <torvalds@osdl.org>
Subject: Re: 2G memory split
References: <20060110125852.GA3389@suse.de>	<20060110132957.GA28666@elte.hu>	<20060110133728.GB3389@suse.de>	<Pine.LNX.4.63.0601100840400.9511@winds.org>	<20060110143931.GM3389@suse.de> <20060110200755.55ee8215.vsu@altlinux.ru>
In-Reply-To: <20060110200755.55ee8215.vsu@altlinux.ru>
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>> +#if defined(CONFIG_DEFAULT_3G)
>> +#define __PAGE_OFFSET_RAW	(0xC0000000)
>> +#elif defined(CONFIG_DEFAULT_3G_OPT)
>> +#define	__PAGE_OFFSET_RAW	(0xB0000000)
>> +#elif defined(CONFIG_DEFAULT_2G)
>> +#define __PAGE_OFFSET_RAW	(0x78000000)
>> +#elif defined(CONFIG_DEFAULT_1G)
>> +#define __PAGE_OFFSET_RAW	(0x40000000)
>> +#else
>> +#error "Bad user/kernel offset"
>> +#endif
>> +
>>  #ifdef __ASSEMBLY__
>> -#define __PAGE_OFFSET		(0xC0000000)
>> +#define __PAGE_OFFSET		__PAGE_OFFSET_RAW
>>  #define __PHYSICAL_START	CONFIG_PHYSICAL_START
>>  #else
>> -#define __PAGE_OFFSET		(0xC0000000UL)
>> +#define __PAGE_OFFSET		((unsigned long)__PAGE_OFFSET_RAW)
>>  #define __PHYSICAL_START	((unsigned long)CONFIG_PHYSICAL_START)
>>  #endif
>>  #define __KERNEL_START		(__PAGE_OFFSET + __PHYSICAL_START)
> 
> Changing PAGE_OFFSET this way would break at least Valgrind (the latest
> release 3.1.0 by default is statically linked at address 0xb0000000, and
> PIE support does not seem to be present in that release).  I remember
> that similar changes were also breaking Lisp implementations (cmucl,
> sbcl), however, I am not really sure about this.
it also breaks some java versions, so we use 3:4 Gb split in OpenVZ, but 
redhat still uses 4:4 in enterprise version, so number of such 
applications should decrease :)

Thanks,
Kirill