question about /proc/kcore

[Jamie Levy]

Hello,

I know this list has been rather quiet for a while...  so I might as
well ask a question :-)

I've been trying to find some information on /proc/kcore and have not
been entirely successful.  I know is that it is an alias to memory,
that is in ELF format, and that can be used with gdb to debug the
kernel.  The `k' seems to imply that it is the kernel's memory, but
all documentation I've found states that it is the size of physical
memory plus 4KB (example below):

https://www.redhat.com/docs/manuals/enterprise/RHEL-4-Manual/en-US/Refere...

This does not seem to be the case, however, when I do a listing in
/proc/kcore on my machine (F8) which has 2 GB of memory:

ls -lh /proc/kcore
-r-------- 1 root root 897M 2008-08-01 19:05 /proc/kcore

I have confirmed the same type of results on other machines to which I
have access.  I also do not seem to have the kcore.h file on my system
(and I have kernel-devel installed), since it is a zero byte file:

-rw-r--r-- 1 root root 0 2008-07-21 02:05
/usr/src/kernels/2.6.25.11-60.fc8-i686/include/config/proc/kcore.h

I am also aware of other tools that can be used to extract information
about kcore like the redhat crash utility:

http://people.redhat.com/anderson/

I am wondering why there is a discrepancy between the documentation
and the actual implementation of the /proc/kcore file?  I would also
like to know where I can find more detailed information about the
kcore file besides the usual description of what it is and how to use
it for debugging.

All the best,

-Jamie Levy

[Astarta]

Jamie Levy wrote:
>  Hello,
>  
>  I know this list has been rather quiet for a while...  so I might as
>  well ask a question :-) 
Hello,

I really thought that this list is completely dead :-)

>  
>  This does not seem to be the case, however, when I do a listing in
>  /proc/kcore on my machine (F8) which has 2 GB of memory:
>  
>  ls -lh /proc/kcore
>  -r-------- 1 root root 897M 2008-08-01 19:05 /proc/kcore
>  
>  I have confirmed the same type of results on other machines to which I
>  have access.  I also do not seem to have the kcore.h file on my system
>  (and I have kernel-devel installed), since it is a zero byte file:
>  
>  -rw-r--r-- 1 root root 0 2008-07-21 02:05
>  /usr/src/kernels/2.6.25.11-60.fc8-i686/include/config/proc/kcore.h
>   

As far as I know, the size of kcore is equal not to the size of _all_ 
physical memory installed on the machine, but just to the amount of 
memory accessible by kernel.
Your kernel seems to be compiled with HIGHMEM support, and if you do `ls 
-l /proc/kcore` you see your LOWMEM size, the real memory that the 
kernel uses. That the reason why the difference you mentioned comes.

Someone will correct me, if I'm wrong :)

>  
>  All the best,
>  
>  -Jamie Levy
>  
>  _______________________________________________
>  Fedora-women-list mailing list
>  Fedora-women-list(a)redhat.com
>  https://www.redhat.com/mailman/listinfo/fedora-women-list 

-- 
with best regards,
Fadeeva Marina.

[Gayathri Swaminathan]

Think Jamie is right.

I have observed behaviour were this file grows based on accessed memory
(would this be kernel shared mem params?)

But it is definitely not just size of physical RAM+4KB on a machine.

gayathri

On Sat, Aug 2, 2008 at 3:54 PM, Astarta <astarta(a)rat.ru&gt; wrote:

>  Jamie Levy wrote:
>
> > Hello,
> >
> > I know this list has been rather quiet for a while...  so I might as
> > well ask a question :-)
> >
>
>  Hello,
>
>  I really thought that this list is completely dead :-)
>
>
> > This does not seem to be the case, however, when I do a listing in
> > /proc/kcore on my machine (F8) which has 2 GB of memory:
> >
> > ls -lh /proc/kcore
> > -r-------- 1 root root 897M 2008-08-01 19:05 /proc/kcore
> >
> > I have confirmed the same type of results on other machines to which I
> > have access.  I also do not seem to have the kcore.h file on my system
> > (and I have kernel-devel installed), since it is a zero byte file:
> >
> > -rw-r--r-- 1 root root 0 2008-07-21 02:05
> > /usr/src/kernels/2.6.25.11-60.fc8-i686/include/config/proc/kcore.h
> >
> >
>
>  As far as I know, the size of kcore is equal not to the size of _all_
>  physical memory installed on the machine, but just to the amount of memory
>  accessible by kernel.
>  Your kernel seems to be compiled with HIGHMEM support, and if you do `ls -l
>  /proc/kcore` you see your LOWMEM size, the real memory that the kernel uses.
>  That the reason why the difference you mentioned comes.
>
>  Someone will correct me, if I'm wrong :)
>
>
> > All the best,
> >
> > -Jamie Levy
> >
> > _______________________________________________
> > Fedora-women-list mailing list
> > Fedora-women-list(a)redhat.com
> > https://www.redhat.com/mailman/listinfo/fedora-women-list
> >
>
>
>  --
>  with best regards,
>  Fadeeva Marina.
>
>
>  _______________________________________________
>  Fedora-women-list mailing list
>  Fedora-women-list(a)redhat.com
>  https://www.redhat.com/mailman/listinfo/fedora-women-list
>  


-- 
Gayathri Swaminathan
gpgkey: 3EFB3D39
Volunteer, FDP

[Jamie Levy]

Thank you both for your responses.  I still have not figured this out,
but I appreciate your replies.  I wasn't sure if this list was still
around, but I thought I would try to liven it up with a question ;-)

All the best,

-Jamie



On Sat, Aug 2, 2008 at 5:58 PM, Gayathri Swaminathan
<gayathri.swa(a)gmail.com&gt; wrote:
>  Think Jamie is right.
>
>  I have observed behaviour were this file grows based on accessed memory
>  (would this be kernel shared mem params?)
>
>  But it is definitely not just size of physical RAM+4KB on a machine.
>
>  gayathri
>
>  On Sat, Aug 2, 2008 at 3:54 PM, Astarta <astarta(a)rat.ru&gt; wrote:
> >
> > Jamie Levy wrote:
> >>
> >> Hello,
> >>
> >> I know this list has been rather quiet for a while...  so I might as
> >> well ask a question :-)
> >
> > Hello,
> >
> > I really thought that this list is completely dead :-)
> >
> >>
> >> This does not seem to be the case, however, when I do a listing in
> >> /proc/kcore on my machine (F8) which has 2 GB of memory:
> >>
> >> ls -lh /proc/kcore
> >> -r-------- 1 root root 897M 2008-08-01 19:05 /proc/kcore
> >>
> >> I have confirmed the same type of results on other machines to which I
> >> have access.  I also do not seem to have the kcore.h file on my system
> >> (and I have kernel-devel installed), since it is a zero byte file:
> >>
> >> -rw-r--r-- 1 root root 0 2008-07-21 02:05
> >> /usr/src/kernels/2.6.25.11-60.fc8-i686/include/config/proc/kcore.h
> >>
> >
> >
> > As far as I know, the size of kcore is equal not to the size of _all_
> > physical memory installed on the machine, but just to the amount of memory
> > accessible by kernel.
> > Your kernel seems to be compiled with HIGHMEM support, and if you do `ls
> > -l /proc/kcore` you see your LOWMEM size, the real memory that the kernel
> > uses. That the reason why the difference you mentioned comes.
> >
> > Someone will correct me, if I'm wrong :)
> >
> >>
> >> All the best,
> >>
> >> -Jamie Levy
> >>
> >> _______________________________________________
> >> Fedora-women-list mailing list
> >> Fedora-women-list(a)redhat.com
> >> https://www.redhat.com/mailman/listinfo/fedora-women-list
> >
> >
> > --
> > with best regards,
> > Fadeeva Marina.
> >
> > _______________________________________________
> > Fedora-women-list mailing list
> > Fedora-women-list(a)redhat.com
> > https://www.redhat.com/mailman/listinfo/fedora-women-list
>
>
>
>  --
>  Gayathri Swaminathan
>  gpgkey: 3EFB3D39
>  Volunteer, FDP
>  


-- 
==============================
 Jamie Levy
 Computer Science Dept
 Queens College
 http://venus.cs.qc.edu/~jlevy
==============================

[Gayathri Swaminathan]

And, thanks for bringing it to life!

There are many RHEL-ish issues/resolutions that I encounter as well.

Will start sharing them here on :)

On Sun, Aug 3, 2008 at 9:31 PM, Jamie Levy <jamie.levy(a)gmail.com&gt; wrote:

>  Thank you both for your responses.  I still have not figured this
> out,
>  but I appreciate your replies.  I wasn't sure if this list was still
>  around, but I thought I would try to liven it up with a question ;-)
>
>  All the best,
>
>  -Jamie
>