Date: Thu, 8 Dec 2016 15:09:43 -0800 From: Mark Johnston <markj@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: Gleb Smirnoff <glebius@freebsd.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r309658 - head/sys/vm Message-ID: <20161208230943.GA25503@wkstn-mjohnston.west.isilon.com> In-Reply-To: <1613947.95yg9mLP0R@ralph.baldwin.cx> References: <201612062252.uB6Mqjhr019191@repo.freebsd.org> <20161207212647.GO27748@FreeBSD.org> <20161207221548.GA33409@wkstn-mjohnston> <1613947.95yg9mLP0R@ralph.baldwin.cx>
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On Thu, Dec 08, 2016 at 07:50:17AM -0800, John Baldwin wrote: > On Wednesday, December 07, 2016 02:15:49 PM Mark Johnston wrote: > > On Wed, Dec 07, 2016 at 01:26:47PM -0800, Gleb Smirnoff wrote: > > > On Tue, Dec 06, 2016 at 10:52:45PM +0000, Mark Johnston wrote: > > > M> Author: markj > > > M> Date: Tue Dec 6 22:52:45 2016 > > > M> New Revision: 309658 > > > M> URL: https://svnweb.freebsd.org/changeset/base/309658 > > > M> > > > M> Log: > > > M> Provide dummy sysctls for v_cache_count and v_tcached. > > > M> > > > M> Some utilities (notably top(1)) exit if any of their input sysctls don't > > > M> exist, and the removal of the above-mentioned PG_CACHE-related sysctls > > > M> makes it difficult to run such utilities on different versions of the > > > M> kernel without recompiling. > > > M> > > > M> Requested by: bde > > > M> > > > M> Modified: > > > M> head/sys/vm/vm_meter.c > > > M> > > > M> Modified: head/sys/vm/vm_meter.c > > > M> ============================================================================== > > > M> --- head/sys/vm/vm_meter.c Tue Dec 6 22:48:28 2016 (r309657) > > > M> +++ head/sys/vm/vm_meter.c Tue Dec 6 22:52:45 2016 (r309658) > > > M> @@ -314,3 +314,14 @@ VM_STATS_VM(v_forkpages, "VM pages affec > > > M> VM_STATS_VM(v_vforkpages, "VM pages affected by vfork()"); > > > M> VM_STATS_VM(v_rforkpages, "VM pages affected by rfork()"); > > > M> VM_STATS_VM(v_kthreadpages, "VM pages affected by fork() by kernel"); > > > M> + > > > M> +#ifndef BURN_BRIDGES > > > M> +/* > > > M> + * Provide compatibility sysctls for the benefit of old utilities which exit > > > M> + * with an error if they cannot be found. > > > M> + */ > > > M> +SYSCTL_UINT(_vm_stats_vm, OID_AUTO, v_cache_count, CTLFLAG_RD, > > > M> + (u_int *)NULL, 0, "Dummy for compatibility"); > > > M> +SYSCTL_UINT(_vm_stats_vm, OID_AUTO, v_tcached, CTLFLAG_RD, > > > M> + (u_int *)NULL, 0, "Dummy for compatibility"); > > > M> +#endif > > > > > > IMHO, there should be some garbage collecting timeout for them. I'd suggest to > > > delete them from head after stable/12 branch is forked. > > > > The intent was to improve compatibility with old userlands, not just to > > help bridge the transition from 11.0 to 12.0. In general I'm all for > > removing cruft, but these sysctls are unobtrusive and I don't see any > > reason to remove them in a specific time frame provided that nothing > > else breaks compatibility for top(1) (and vmstat(8)). Please feel free > > to add a timeout if you still disagree, though. > > I would suggest sticking them under COMPAT_FREEBSD11 then. That would give > users control via the COMPAT_FREEBSD<x> options the way we do with other > compat shims. The only nit is you need to add the COMPAT_FREEBSD11 option > first (probably in a separate commit). Ok. I've put up a CR here if anyone would like to take a look first: https://reviews.freebsd.org/D8736
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