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

["J.A. Magallon" <jamagallon@able.es>]

On Tue, 10 Jan 2006 14:16:19 -0500, Mark Lord <lkml@rtr.ca> wrote:

> Okay, fixed the ordering of the "default" lines
> so that the Kconfig actually works correctly.
> 
> Best for Andrew to soak this one in -mm.
> 
> Signed-off-by:  Mark Lord <mlord@pobox.com>
> 

Working nice on top of 2.6.15-mm2.
Even with the 'evil binary' nVidia driver 8178 ;).
In fact, I have been using the 1Gb-lowmem patch on -mm and the nVidia
driver since long ago, without problems.

I really like to see this in -mm, and finally in mainline.

My only objection is about the menu entry names and help. I think
people building a kernel would not exactly understand what all this is
about (even I think I don't have it realle clear).

Is there any doc which states clearly somthing like:

- no highmem is the fastest
- 4Gb introduces one indirection, so it is slower...(really ?)
- 64Gb introduces two (PAE ?)

mixed with

- 3G/1G standard maping:
   - nor user nor kernel can use any memory above 860 Mb
   - user processes (my numbercruncher) can not allocate more than XGb
- 2G/2G: idem:
   - max memory seen by my linux system (not kernel, but kernel+userspace,
   - how much can I allocate for a single process (how big my problem
     can be ?)

If there is already a doc like that, it would be very interesting to
have pointer/link to it in the help text.

For example, when I read this:

+	  If the address range available to the kernel is less than the
+	  physical memory installed, the remaining memory will be available
+	  as "high memory". Accessing high memory is a little more costly
+	  than low memory, as it needs to be mapped into the kernel first.

Does this mean that with 3/1 standard split, I still can use the lost
128 Mb for something ? I though I can't.

Don't be too hard with me, just anxious to finally understand this...

--
J.A. Magallon <jamagallon()able!es>     \               Software is like sex:
werewolf!able!es                         \         It's better when it's free
Mandriva Linux release 2006.1 (Cooker) for i586
Linux 2.6.15-jam2 (gcc 4.0.2 (4.0.2-1mdk for Mandriva Linux release 2006.1))

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