Date: Thu, 6 Jun 2019 14:35:52 -0400 From: Mark Johnston <markj@freebsd.org> To: Alan Somers <asomers@freebsd.org> Cc: src-committers <src-committers@freebsd.org>, svn-src-all <svn-src-all@freebsd.org>, svn-src-head <svn-src-head@freebsd.org> Subject: Re: svn commit: r348737 - head/sys/kern Message-ID: <20190606183552.GD3015@raichu> In-Reply-To: <CAOtMX2jvfnXx35DoV3JBGeVcm%2BDtbd4HWmqFBSNNEbGO4eBa9Q@mail.gmail.com> References: <201906061504.x56F4odw034764@repo.freebsd.org> <201906061735.x56HZGIJ058845@gndrsh.dnsmgr.net> <CAOtMX2iQ=Q9tR2MviXQDRqs_UNW6gQq=BGiDpNwXbpWjG%2BH7CQ@mail.gmail.com> <c6d9a869-d678-212b-0bc6-d0046f892e76@FreeBSD.org> <CAOtMX2jvfnXx35DoV3JBGeVcm%2BDtbd4HWmqFBSNNEbGO4eBa9Q@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Thu, Jun 06, 2019 at 12:04:52PM -0600, Alan Somers wrote: > On Thu, Jun 6, 2019 at 12:01 PM John Baldwin <jhb@freebsd.org> wrote: > > > > On 6/6/19 10:39 AM, Alan Somers wrote: > > > On Thu, Jun 6, 2019 at 11:35 AM Rodney W. Grimes > > > <freebsd@gndrsh.dnsmgr.net> wrote: > > >> > > >>> Author: asomers > > >>> Date: Thu Jun 6 15:04:50 2019 > > >>> New Revision: 348737 > > >>> URL: https://svnweb.freebsd.org/changeset/base/348737 > > >>> > > >>> Log: > > >>> Add a testing facility to manually reclaim a vnode > > >>> > > >>> Add the debug.try_reclaim_vnode sysctl. When a pathname is written to it, it > > >>> will be reclaimed, as long as it isn't already or doomed. The purpose is to > > >>> gain test coverage for vnode reclamation, which is otherwise hard to > > >>> achieve. > > >>> > > >>> Add the debug.ftry_reclaim_vnode sysctl. It does the same thing, except > > >>> that its argument is a file descriptor instead of a pathname. > > >> > > >> Should not this all be wrapped in some #ifdef or other protection, > > >> is it really a good idea to have this on every single box running > > >> FreeBSD? > > > > > > I initially thought so too, but kib thought that it could be useful > > > for debugging problems in the field. The potential downside is > > > limited, because only root can write to the sysctls, and the > > > worse-case damage is similar to a "umount -f". > > > > A compromise might be to stick this in a kernel module instead of in the > > base kernel. You could still kldload it in the field for debugging but > > not necessarily have it directly available out of the box. > > > > -- > > John Baldwin > > If we already had such a module, it would make sense to put these > sysctls in there. But I don't want to create an entire module for > just a few dozen LOC. Nor do I want to mediate a bike shed. So let's > vote. kib already registered a vote for making them available all of > the time. rgrimes voted to guard them by INVARIANTS. Anybody else > who cares can reply to this thread. I'll count the votes in 24 hours. +1 to making it unconditional. We already have lots of debugging sysctls enabled in !INVARIANTS kernels, and these sorts of things end up being handy in unexpected ways. For a long time I've carried a patch which unconditionally compiles debug.vm_lowmem because I kept having to recompile to get it.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20190606183552.GD3015>