Date: Wed, 23 Feb 2011 15:13:24 GMT From: Martin Simmons <martin@lispworks.com> To: freebsd-fs@freebsd.org Subject: Re: Why is procfs deprecated in favor of procstat? Message-ID: <201102231513.p1NFDOw4031044@higson.cam.lispworks.com> In-Reply-To: <20110222211444.GD78089@deviant.kiev.zoral.com.ua> (message from Kostik Belousov on Tue, 22 Feb 2011 23:14:44 %2B0200) References: <201102211707.p1LH7c8n075660@lurza.secnetix.de> <476667.58379.qm@web121516.mail.ne1.yahoo.com> <20110222095211.GA96223@icarus.home.lan> <201102220931.17733.jhb@freebsd.org> <alpine.GSO.2.01.1102221304163.7969@freddy.simplesystems.org> <20110222211444.GD78089@deviant.kiev.zoral.com.ua>
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>>>>> 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. __Martin
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