porting an app that checks /proc/meminfo

[Brooks Davis]

[Please don't top post on freebsd lists.]

On Wed, Jan 25, 2006 at 08:06:13AM -0800, Jeremy Chadwick wrote:
> 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

I was refering to sysctl.  A few of the kvm calls are usable as wrappers
to sysctl calls, but I don't really think that's a good idea unless you
need to support core dumps in your utility.

> 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.

That's basicly correct.

-- Brooks

> -- 
> | 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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