Re: SRM vs ARC
On Sunday, 31 Jan, Oscar Levi wrote:
> >
> > [cassiel:linux]$ size vmlinux
> > text data bss dec hex filename
> > 1222869 216904 198988 1638761 190169 vmlinux
> >
> > The in-memory size of your kernel will be about 1.5MB.
> >
>
> Oh, duh. Are the allocated buffers visible from 'free'? In other
> words, is the kernel image the only memory consumption hidden from
> free? Do we lose something, .5MB, where the BIOS ROMS are located?
>
The breakdown is as follows.
Total memory as reported by `free' is counted as the full memory size
minus reserved pages. The number of reserved pages is shown on the
console when you press Shift-ScrollLock. Reserved pages come from the
following sources:
- Console (SRM or MILO): most of these contain the in-memory console
image, which is preserved all the time Linux is running (MILO is kept
compressed). The rest comprises PALcode and HWRPB (9 pages).
Current MILOs always report as taking up half a megabyte (an
overestimate), bringing total to 73; newer MILOs will report their
actual size.
- Kernel image: the size is as reported by `size' plus some very small
amount spent on alignments.
- "Static" kernel structures, allocated during startup, such as the
memory map. On my machine with 64 Mb RAM running 2.1.131 these
consume 98 pages.
On 2.1 and 2.2 kernels, some memory belonging to the kernel image is
freed after the initialisation (usually 8 pages).
For example, this is how it looks on my machine:
MILO: 73
vmlinux: 206
kernel allocated: 98
freed: -8
------------------------
Total reserved: 369 pages (2952 kB)
$ free
total used free shared buffers cached
Mem: 62584 60768 1816 30792 3304 25272
-/+ buffers/cache: 32192 30392
Swap: 131064 14216 116848
Nikita
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