porting an app that checks /proc/meminfo

[Jeremy Chadwick]

I believe the calls he's referring to are the kvm*(3) calls and the
sysctl*(3) calls.  Here's a list:

kvm(3)                   - kernel memory interface
kvm_geterr(3)            - get error message on kvm descriptor
kvm_getfiles(3)          - survey open files
kvm_getloadavg(3)        - get load average of the system
kvm_getprocs(3), kvm_getargv(3), kvm_getenvv(3) - access user process state
kvm_getswapinfo(3)       - return swap summary statistics for the system
kvm_nlist(3)             - retrieve symbol table names from a kernel image
kvm_open(3), kvm_openfiles(3), kvm_close(3) - initialize kernel virtual memory access
kvm_read(3), kvm_write(3) - read or write kernel virtual memory
sysctl(3), sysctlbyname(3), sysctlnametomib(3) - get or set system information

Secondly, yes, these are "BSD" specific.  I believe these will work
on NetBSD, OpenBSD, and FreeBSD (4, 5, 6, and 7); however, some of
the BSDs handle the kvm*(3) differently (some need to be linked with
libkvm, others do not).

Thirdly, no, there is no standardised way to get VM/system information
from different operating systems.  Linux nuts use /proc, BSD folk use
the above, Solaris folk use whatever Solaris has (I honestly forget
but probably some subset of kvm), and so on and so forth.

To anyone else: if I'm wrong, please correct me.

-- 
| Jeremy Chadwick                                 jdc at parodius.com |
| Parodius Networking                        http://www.parodius.com/ |
| UNIX Systems Administrator                   Mountain View, CA, USA |
| Making life hard for others since 1977.                             |

On Wed, Jan 25, 2006 at 10:02:28AM -0300, Fernan Aguero wrote:
> +----[ Brooks Davis <brooks at one-eyed-alien.net> (24.Jan.2006 23:06):
> |
> | On Tue, Jan 24, 2006 at 03:56:57PM -0200, Rainer Alves wrote:
> | > Fernan Aguero wrote:
> | > >The program builds fine, but because it uses /proc/meminfo
> | > >to check for available memory, when you run it, it will
> | > >complain about the lack of /proc/meminfo and won't let you
> | > >do anything. 
> | > >
> | > ...
> | > >How does one gets the values of i) memory used by the
> | > >program/process and ii) amount of RAM available in the
> | > >computer without using /proc/meminfo in FreeBSD? 
> | > 
> | > Take a loot at sysutils/muse, which uses /dev/mem to gather this info:
> | 
> | Please don't do this.  Really!  There's no point in gratuitously
> | groveling around in the kernel's live memory image to get data you have
> | access to via unprivileged calls.
> |
> +----]
> 
> Brooks,
> 
> what are these unprivileged calls? can you list a few so we
> can check the corresponding man pages? Are they BSD
> specific?
> 
> Again I'm not versed in C so what follows is just what I
> could grasp from a few google searches.
> 
> It seems like in linux you can also use unprivileged calls
> to get this info, but you have also the option of using the
> /proc filesystem. I don't know what are these unprivileged
> calls like in linux ... but perhaps they are pretty standard
> across systems?
> 
> I'm not positive about this but I just have the impression
> that there should be a generic (not linux-specific or BSD
> specific) way to get this info, like a generic call that has
> the same name and similar arguments across different OS (of
> course the internal implementation should be different in
> each OS) ... does such thing exist?
> 
> Fernan
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