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