Hello,
I tried to get the amount of total physical memory. I looked at /proc/meminfo
and found this line (2.4.18):
MemTotal: 30844 kB
But this is not correct the system have 32768 kB Memory. I looked at kernel
sources and I found the variable max_mapnr. Can I use it to detect the
correct memory size? It seems that it stores the maximum number of pages
usable. So I can convert it with macro K() in linux/fs/proc/proc_misc.c to a
value in kB.
But there are 1924 kB not available (32768 kB - 30844 kB). On system boot I
get the following message:
Memory: 30780k available (960k kernel code, 392k data, 64k init, 0k highmem)
So I calculated:
1924 kB
-960 kB Kernel
- 392 kB Data
- 64 kB Init
--------------------
508 kB
There are 508 kB lost (?) memory. It seems the boot allocator is reserving
this memory, but linux doesn't tell for what. I want to know for what the 508
kB are. Is the kernel stack included in the 508 kB or in the 30844 kB. I
don't think so, because the value 30844 kB isn't changing after boot. And
every process should allocate 8 kB kernel stack.
Best Regards
J?rgen Urban
--
J?rgen Urban <[email protected]>
Software Engineer
SYSGO Real-Time Solutions AG
Am Pfaffenstein 14
55270 Klein-Winternheim, Germany
Telefon: +49-6136-9948-0
FAX: +49-6136-9948-10
http://www.sysgo.com
On Monday 19 January 2004 12:22, J?rgen Urban wrote:
> Hello,
>
> I tried to get the amount of total physical memory. I looked at
> /proc/meminfo and found this line (2.4.18):
>
> MemTotal: 30844 kB
>
> But this is not correct the system have 32768 kB Memory. I looked at
> kernel sources and I found the variable max_mapnr. Can I use it to detect
> the correct memory size? It seems that it stores the maximum number of
> pages usable. So I can convert it with macro K() in
> linux/fs/proc/proc_misc.c to a value in kB.
There are some addresses that cannot be used on PC because there is
something mapped (for example System ROM...), you can see these regions
doing "cat /proc/iomem".
Here there is my output:
00000000-0009fbff : System RAM
0009fc00-0009ffff : reserved
000a0000-000bffff : Video RAM area
000c0000-000c7fff : Video ROM
000f0000-000fffff : System ROM
00100000-07febfff : System RAM
00100000-00298596 : Kernel code
00298597-00322f27 : Kernel data
07fec000-07feefff : ACPI Tables
07fef000-07ffefff : reserved
07fff000-07ffffff : ACPI Non-volatile Storage
de800000-de81ffff : Promise Technology, Inc. 20265
df000000-df0000ff : Cologne Chip Designs GmbH ISDN network controller
[HFC-PCI]
df800000-df8000ff : Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+
df800000-df8000ff : 8139too
e0000000-e3dfffff : PCI Bus #01
e0000000-e1ffffff : 3Dfx Interactive, Inc. Voodoo Banshee
e3f00000-e5ffffff : PCI Bus #01
e4000000-e5ffffff : 3Dfx Interactive, Inc. Voodoo Banshee
e6000000-e7ffffff : VIA Technologies, Inc. VT8363/8365 [KT133/KM133]
ffff0000-ffffffff : reserved
Bye
--
Paolo Ornati
Linux v2.4.24
On Mon, Jan 19, 2004 at 06:58:05PM +0100, Paolo Ornati wrote:
> On Monday 19 January 2004 12:22, J?rgen Urban wrote:
> > Hello,
> >
> > I tried to get the amount of total physical memory. I looked at
> > /proc/meminfo and found this line (2.4.18):
> >
> > MemTotal: 30844 kB
> >
> > But this is not correct the system have 32768 kB Memory. I looked at
> > kernel sources and I found the variable max_mapnr. Can I use it to detect
> > the correct memory size? It seems that it stores the maximum number of
> > pages usable. So I can convert it with macro K() in
> > linux/fs/proc/proc_misc.c to a value in kB.
>
> There are some addresses that cannot be used on PC because there is
> something mapped (for example System ROM...), you can see these regions
> doing "cat /proc/iomem".
That's usually just a few KB, but don't forget that MemTotal is what's left
after kernel memory is mapped.