Re: [PATCH ] VMSPLIT config options (with default config fixed)

[Jan Engelhardt]

>
>> glad to see that the linux kernel is now ready for the 'idea'
>> I submitted a patch[1] for, more than a year ago -- which
>> unfortunately went unnoticed back then ...

BTW, I patched my local 2.6.16-rc1 with that patch and I run off 
VMSPLIT_3G_OPT quite well without problems. (Well, VMware gets it wrong, as 
usual, but nothing that I could not solved.) Even though I do not even have 
1 G but just 768 ;-)

This sort of testing reminds me of Linus's 100->1000 Hz change
("I chose 1000 originally partly as a way to make sure that people that
    assumed HZ was 100 would get a swift kick in the pants.")

Could we also do that with VMSPLIT?
("Let's choose VMSPLIT_2G to make sure that i386-people that assumed
PAGE_OFFSET was 0xC0000000 would get...")

>Hm, I wonder if we could have a more fine-grained choice of the
>boundary? There are also systems around with e.g. 1.25G or 1.5G of
>main memory.
>

Maybe something like:

        config VMSPLIT_1G
                bool "1G/3G user/kernel split"
        config VMSPLIT_X
                bool "Manual split"
endchoice

config VMSPLIT_MANUAL
    depends on VMSPLIT_X
    hex
    default 0xC0000000
    prompt "Memory split address (must be aligned to 4096)"


And in include/asm/page.h:

	#ifdef CONFIG_VMSPLIT_MANUAL
	#define __PAGE_OFFSET ((unsigned long)CONFIG_VMSPLIT_MANUAL)
	#else
	#define __PAGE_OFFSET ((unsigned long)CONFIG_PAGE_OFFSET)
	#endif

Not perfect, but a start.



Jan Engelhardt
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