Hi Pannaga!
Use the mem= parameter on the kernel command-line to specify less memory
than what is available. Then you can use the last unused chunk of memory,
e.g. if you have 256M memory and you want to "steal" a 40M chunk at the end:
mem=216M
> Hi all,
> 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 = .;
>
> First, I put these lines in code segment and found that 'my_size'
> cannot go beyond 0x500000(5MB) . Any larger value , the kernel image
> refuses to
> boot up. I found the same problem with these lines being in data segment
> or in the bss segment.
>
> But putting these line after
>
> _end = .;
>
> line in vmlinux.lds, I am able to give 0x1700000(17MB) to my_size and
> still boot with that kernel image.
>
> My questions are :
>
> 1. Is there any other way I can get to keep 40MB(or even 20MB) of
> contiguous kernel memory space ?
>
> 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).
> if yes, are the pages corresponding to this region swappable or
> is it that since this hole appears in kernel image, it is locked to a
> physical space
> and this is never swapped. (basically, i want by data in kernel space
> always available to kernel without having to bother abt swapping the
> pages back)
>
> Thanx in advance,
> Pannaga Bhushan
>
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--Regards Abraham
UNIX enhancements aren't.
__________________________________________________________ Abraham vd Merwe - 2d3D, Inc.
Device Driver Development, Outsourcing, Embedded Systems
Cell: +27 82 565 4451 Snailmail: Tel: +27 21 761 7549 Block C, Aintree Park Fax: +27 21 761 7648 Doncaster Road Email: abraham@2d3d.co.za Kenilworth, 7700 Http: http://www.2d3d.com South Africa
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