Re: vmalloc kernel parameter

[Rodrigo Amestica <ramestic@nrao.edu>]

Hi Sergey,

the uppermem workaround for grub did not work well for me when I tried to add 
the mem+memmap parameters to the kernel. My machine has 2GB of ram and trying to 
set mem beyond the 1GB limit made the machine unable to boot. Setting mem to a 
value below 1GB allowed the machine to boot but VmallocTotal reported unexpected 
values.

I have switched now to lilo and things seems to work just fine. The following 
lilo config

 image=/boot/vmlinuz
        label=vmalloc
        initrd=/boot/initrd.img
        read-only
        append="root=LABEL=/ vmalloc=256M mem=1899M memmap=128M#1899M"

let's the machine boot just fine reporting the following values in /proc/meminfo

MemTotal:      1925632 kB
VmallocTotal:   245752 kB

Rodrigo

Rodrigo Amestica wrote:
> Hi Sergey, many thanks for the reply.
>
> I saw those links before but I did not get their full meaning.
>
> By setting uppermem to 512M it does actually work. However, now I'm 
> trying to reserve RAM for DMA sake. For that I use mem=1899M; where 1899 
> comes from the total memory reported under normal booting less 128M, 
> which are the Megs that I'm trying to reserve.
>
> It seems that by adding mem to the boot line goes into conflicting with 
> the uppermem+vmalloc arrangement.
>
> Without providing more details on what's actually happening can you tell 
> that there is something wrong on what I'm trying to do?
>
> Would switching to lilo help any?
>
> thanks,
>  Rodrigo
>
> Sergey Vlasov wrote:
> > This is a known problem with GRUB: it tries to put initrd at the highest
> > possible address in memory, and assumes the standard vmalloc area size.
> > You need to trick GRUB into thinking that your machine has less memory
> > by using "uppermem 524288" (512M) or even lower - then the initrd data
> > will still be accessible for the kernel even with larger vmalloc area.
> >
> > http://lkml.org/lkml/2005/4/4/283
> > http://lists.linbit.com/pipermail/drbd-user/2005-April/002890.html
> >
> > > ps: my kernel version is 2.6.15.2, and my machine is a dual opteron
> > > with 2GB of ram
> > >
> > > title with vmalloc
> > >          root (hd0,0)
> >
> > Add "uppermem 524288" here.
> >
> > >          kernel /boot/vmlinuz ro root=LABEL=/ vmalloc=256M
> > >          initrd /boot/initrd.img
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