Why is procfs deprecated in favor of procstat?

[Kostik Belousov]

On Wed, Feb 23, 2011 at 03:13:24PM +0000, Martin Simmons wrote:
> >>>>> On Tue, 22 Feb 2011 23:14:44 +0200, Kostik Belousov said:
> > 
> > On Tue, Feb 22, 2011 at 01:10:57PM -0600, Bob Friesenhahn wrote:
> > > On Tue, 22 Feb 2011, John Baldwin wrote:
> > > >
> > > >Actually, the replacement for procfs is not sysctl, but ptrace(2), and
> > > >there
> > > 
> > > I have been following this discussion with my jaw agape.  It seems 
> > > that the many men standing around this elephant are all perceiving 
> > > completely different things based on their own interests and 
> > > experiences.
> > > 
> > > My own software is using procfs to efficiently determine the path to 
> > > the currently running executable.  I am sure that other software does 
> > > the same since Linux procfs (and probably OS X) supports the same 
> > > mechanism.  It is difficult to imagine how this would be done via 
> > > ptrace(2).
> > Look at the PT_VM_TIMESTAMP + PT_VM_ENTRY. You would iterate over
> > the the mappings in the address space and look at the binaries at
> > pve_path, if any. The one that is elf object f the ET_EXEC type
> > is the binary. It is somewhat clumsy but the end result is the same
> > as if reading /proc/<pid>/file.
> > 
> > Or, you use sysctl kern.proc.vmmap and get essentially the same data.
> > PT_VM_ENTRY was added long after the sysctl, I did not objected exactly
> > because ptrace(2) looked more logical.
> > 
> > The advantage of using procfs or sysctl instead of ptrace(2) is that
> > you do not need to attach as debugger, causing the issues with signal
> > delivery for the debugee.
> 
> Another advantage I find of (linux) procfs is that you always get a textual
> version of it, which can be useful in shell scripts and debugging situations.
> 
> /sbin/sysctl kern.proc.vmmap isn't usable because the command has no way to
> specify the pid.
> 
> /usr/bin/procstat gives access to only part of the procfs and sysctl
> namespace.

Apparently, there is kern.proc.pathname sysctl and -b switch to procstat.
I never claimed that sysctls are useful from the command line, rather,
they form a binary interface for the programs.
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