Re: [PATCH] 1-2-3 GB

[Albert D. Cahalan]

Andrea Arcangeli writes:
> On Fri, Jan 11, 2002 at 11:32:37PM -0800, H. Peter Anvin wrote:
>> By author:    [e-mail]

>>> --- linux.aa2/arch/i386/config.in       Fri Jan 11 20:57:58 2002
>>> +++ linux/arch/i386/config.in   Fri Jan 11 22:20:32 2002
>>> @@ -169,7 +169,11 @@
>>>  if [ "$CONFIG_HIGHMEM64G" = "y" ]; then
>>>     define_bool CONFIG_X86_PAE y
>>>  else
>>> -   bool '3.5GB user address space' CONFIG_05GB
>>> +   choice 'Maximum Virtual Memory' \
>>> +       "3GB            CONFIG_1GB \
>>> +        2GB            CONFIG_2GB \
>>> +        1GB            CONFIG_3GB \
>>> +        05GB           CONFIG_05GB" 3GB
>>>  fi
>>
>> Calling this "Maximum Virtual Memory" is misleading at best.  This is
>> best described as "kernel:user split" (3:1, 2:2, 1:3, 3.5:0.5);
>> "maximum virtual memory" sounds to me a lot like the opposite of what
>> your parameter is.
>
> actually it is really max virtual memory.. but from the user point of
> view, user is supposed to care about the virtual memory he can manage,
> not about what the kernel will do with the rest. So if the user wants
> 3GB of virtual memory available to each task he will select 3GB. I
> really don't mind if you want to change it from the kernel point of
> view, but given it's the user who's supposed to compile it, also the
> current patch looks good enough to me.

The numbers are wrong anyway, because of vmalloc() and PCI space.
The PCI space is motherboard-dependent AFAIK, but you could at
least account for the 128 MB vmalloc() area:

user virtual space / non-kmap physical memory

3584/384
3072/896
2048/1920
1024/2944  (sure this works, even for syscalls w/ bad pointers?)
512/3456   (sure this works, even for syscalls w/ bad pointers?)