Note: this question really belongs on <[EMAIL PROTECTED]>.
[Pannaga Bhushan]
> I am looking for a setup where I need to have a certain amount
> of data always available to the kernel. The size of data I am looking
> at is abt 40MB(preferably, but I will settle for 20MB too) . So the
> normal kmalloc will not help me. So what I did was, I created a hole
> in kernel space by putting the following line in vmlinux.lds
>
> ALIGN(4096);
> __hole_start = .;
> . = . + 0xmy_size;
> __hole_end = .;
I assume you also tried the old-fashioned C method:
#include <asm/page.h>
static char __hole_start[0xmy_size] __attribute__((__aligned__(PAGE_SIZE)));
Did that not work either?
> 1. Is there any other way I can get to keep 40MB(or even 20MB) of
> contiguous kernel memory space ?
There used to be a patch out there called `bigphysarea' - look around,
perhaps someone is still maintaining it. It should do what you want.
> 2. Abt the 17MB hole, I am able to use after the _end = .;
> .... is this 17MB really there in kernel image?('cos it isn't in
> any segment and also it appears after _end).
I doubt it is accessible, but that is really uninformed speculation on
my part.
> (basically, i want by data in kernel space always available to kernel
> without having to bother abt swapping the pages back)
User space could allocate this space and then call mlockall(). That
does not guarantee *physically* contiguous space, though, and is only
accessible within to the address space of that one process.
Peter
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