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SubjectRe: Reserved memory
Rui Sousa wrote:

> Hi,
>
> Can someone explain me what is happening here?
>
> kernel 2.2.14 SMP:
>
> Jan 25 01:03:45 localhost kernel:
> Memory: 128392k/131072k available (692k kernel code, 424k reserved, 1516k data,
> 48k init)
>
> kernel 2.3.42 SMP:
>
> Feb 3 18:48:29 localhost kernel: e820: 0009fc00 @ 00000000 (usable)
> Feb 3 18:48:29 localhost kernel: e820: 00000400 @ 0009fc00 (reserved)
> Feb 3 18:48:29 localhost kernel: e820: 00020000 @ 000e0000 (reserved)
> Feb 3 18:48:29 localhost kernel: e820: 07f00000 @ 00100000 (usable)
> Feb 3 18:48:29 localhost kernel: e820: 00001000 @ fec00000 (reserved)
> Feb 3 18:48:29 localhost kernel: e820: 00001000 @ fee00000 (reserved)
> Feb 3 18:48:29 localhost kernel: e820: 00040000 @ fffc0000 (reserved)
> ....
> Feb 3 18:48:29 localhost kernel: zone(0): 4096 pages.
> Feb 3 18:48:29 localhost kernel: zone(1): 28672 pages.
> Feb 3 18:48:29 localhost kernel: zone(2): 0 pages.
> ....
> Feb 3 18:48:29 localhost kernel: Memory: 126424k/131072k available (1103k
> kernel code, 4260k reserved, 105k data, 152k init, 0k highmem)
>
> These are similarly configured kernels. kernel code + data got smaller which is
> good. init
> is bigger but it doesn't matter. What's up with the ~ 4 MB of reserved memory?
> Does it make
> sense or not? For what is it reserved?
>
> Rui Sousa

Rui, I dont know if you got your answer yet or not but the boot-time accounting of

memory utilization changed between 2.2 and 2.3. As memory is allocated by the
kernel at boot time it is marked as "reserved". In 2.2 that reserved memory is
carefully
divided into "kernel code", "data", "init" and what is left over is "reserved".
In 2.3
memory that is allocated at boot time is still marked as "reserved" but the "data"
size
only includes the data section of the vmlinux kernel itself, not what is allocated
at boot
time by the kernel. This accounts for most of the larger "reserved" size in 2.3,
then
the additional 2MB is just a larger overall kernel. Perhaps there were more
modules
in your 2.2 than there is in your 2.3 kernel configuration.

Larry Woodman

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