Date: Wed, 23 Feb 2011 17:34:19 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: Martin Simmons <martin@lispworks.com> Cc: freebsd-fs@freebsd.org Subject: Re: Why is procfs deprecated in favor of procstat? Message-ID: <20110223153419.GQ78089@deviant.kiev.zoral.com.ua> In-Reply-To: <201102231513.p1NFDOw4031044@higson.cam.lispworks.com> 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> <201102231513.p1NFDOw4031044@higson.cam.lispworks.com>
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[-- Attachment #1 --] 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. [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (FreeBSD) iEYEARECAAYFAk1lKPoACgkQC3+MBN1Mb4h40QCfaX563yW53iGI6besxmMkbCcv gkMAn0aDetdGj8xoSnL8apFxJBDDE981 =tG46 -----END PGP SIGNATURE-----
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