kcore

Walter Cazzola cazzola at dico.unimi.it
Wed Apr 20 07:48:49 UTC 2011


On Tue, 19 Apr 2011, Robert Nichols wrote:

> On 04/19/2011 07:08 PM, Patrick Dupre wrote:
>> Hello,
>>
>> I have a /proc/kcore file which is huge: 1059057664
>> Is it normal ?
>
> Everything in /proc is just a window into various kernel data structures.
> The pseudo-filesystem you see there doesn't exist on disk.  In your case,
> that kcore "file" just allows read-access to the ~1GiB of virtual memory
> in your 32-bit kernel's address space.  For my 64-bit kernel:
>
>  -r--------. 1 root root 140737486266368 2011-04-19 22:13:33 /proc/kcore
>
> I can assure you that I don't have ~128 terabytes of disk storage or
> physical memory on this system.

I'm puzzled, my kcore shows exactly the size you reported (and I just
have 8Gb of RAM) but from the proc manual I get:

   /proc/kcore
          This file represents the physical memory of the system and is
          stored in the ELF core file format.  With this pseudo-file, and
          an unstripped kernel (/usr/src/linux/vmlinux) binary, GDB can
          be used to examine the current state of any kernel data
          structures.

          The total length of the file is the size of physical memory
          (RAM) plus 4KB.

So 8Gb are quite far from 128Tb (even if considering the 4KB extra) so
somewhere there should be a mistake, where?

Walter
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