On Thu, 3 Apr 2008, Balaji Rao wrote:
> Hi Robert,
>
> Out of the 1G logical address space the kernel sees, 128MB is eaten up by
> VMALLOC_RESERVE for establishing (temporary) mappings into high memory,
> leaving only 896 MB as low memory.
>
> The definition for that 128 MB is found in arch/x86/mm/init_32.c as
>
> unsigned int __VMALLOC_RESERVE = 128 << 20;
>
> > * can it be changed at kernel config time?
>
> Apparently it can't be changed..
ah, but it apparently *can* be changed at boot time; see
arch/x86/kernel/setup_32.c:
...
/*
* vmalloc=size forces the vmalloc area to be exactly 'size'
* bytes. This can be used to increase (or decrease) the
* vmalloc area - the default is 128m.
*/
static int __init parse_vmalloc(char *arg)
{
if (!arg)
return -EINVAL;
__VMALLOC_RESERVE = memparse(arg, &arg);
return 0;
}
early_param("vmalloc", parse_vmalloc);
...
that's useful to know.
rday
--
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry:
Have classroom, will lecture.
http://crashcourse.ca Waterloo, Ontario, CANADA
========================================================================
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