Date: Sat, 18 Jan 2003 13:20:28 -0700 From: Scott Long <scott_long@btc.adaptec.com> To: Hiten Pandya <hiten@unixdaemons.com> Cc: Craig Rodrigues <rodrigc@attbi.com>, Will Andrews <will@csociety.org>, Joe Marcus Clarke <marcus@marcuscom.com>, freebsd-current@freebsd.org, dillon@freebsd.org Subject: Re: VM_METER no longer defined? Message-ID: <3E29B70C.9070500@btc.adaptec.com> In-Reply-To: <XFMail.20030117052330.conrads@cox.net> References: <XFMail.20030117052330.conrads@cox.net> <3E284083.3030504@btc.adaptec.com> <1042826526.328.24.camel@gyros> <20030117182610.GR30015@procyon.firepipe.net> <20030117232821.GA5237@attbi.com> <3E28943E.3000702@btc.adaptec.com> <20030118142031.GA96568@unixdaemons.com>
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Hiten Pandya wrote:
> On Fri, Jan 17, 2003 at 04:39:42PM -0700, Scott Long wrote the words
> in effect of:
>
> >Craig Rodrigues wrote:
> >
> >
> >>On Fri, Jan 17, 2003 at 10:26:10AM -0800, Will Andrews wrote:
> >>
> >>
> >>>Of course, these things can be fixed. But I consider this change
> >>>gratuitous and it breaks standard compatability rules: deprecate
> >>>for one major version and remove in the second. I haven't seen
> >>>any reason why this couldn't be added to vm/vm_param.h:
> >>>
> >>>#define VM_METER VM_TOTAL
> >>>
> >>>for compatability purposes. This change is way too sudden in an
> >>>external API (if it's supposed to be internal, then protect it
> >>>with an #ifdef _KERNEL already!).
> >>
> >>
> >>How about this then:
> >>
> >>
> >>Index: vm_param.h
> >>===================================================================
> >>RCS file: /home/ncvs/src/sys/vm/vm_param.h,v
> >>retrieving revision 1.16
> >>diff -u -r1.16 vm_param.h
> >>--- vm_param.h 2003/01/11 07:29:46 1.16
> >>+++ vm_param.h 2003/01/17 23:25:52
> >>@@ -89,6 +89,8 @@
> >>#define VM_SWAPPING_ENABLED 11 /* swapping enabled */
> >>#define VM_MAXID 12 /* number of valid vm ids */
> >>
> >>+#define VM_METER VM_TOTAL /* backwards compatibility, struct vmmeter
> >>*/
> >>+
> >>#define CTL_VM_NAMES { \
> >> { 0, 0 }, \
> >> { "vmtotal", CTLTYPE_STRUCT }, \
> >>
> >>
> >>
> >>
> >>
> >>The only place where VM_METER is used in this directory was in
> vm_meter.c:
> >>
> >> 240 SYSCTL_PROC(_vm, VM_METER, vmmeter, CTLTYPE_OPAQUE|CTLFLAG_RD,
> >> 241 0, sizeof(struct vmtotal), vmtotal, "S,vmtotal",
> >> 242 "System virtual memory statistics");
> >>
> >>This changed to:
> >>
> >> 240 SYSCTL_PROC(_vm, VM_TOTAL, vmtotal, CTLTYPE_OPAQUE|CTLFLAG_RD,
> >> 241 0, sizeof(struct vmtotal), vmtotal, "S,vmtotal",
> >> 242 "System virtual memory statistics");
> >>
> >>
> >>
> >
> >This is ugly and only further perpetuates what appears to be a
> >gratuitous API
> >change. Let's wait to hear from the submitter (Hiten) and committer
> >(Matt) to
> >see why this was needed in the first place.
> >
> >Hiten? Matt?
>
>
> The change was made, because VM_METER was a bogus name for what it did.
> It returned struct vmtotal, but we named it VM_METER. Infact, I tried
> to push this change some long time ago, but there were complications
> (people busy etc...).
>
> I think applicatins to should be changed to use VM_TOTAL, instead of
> VM_METER, because that's the correct name. This is the same issue with
> the KMEM_METER define, which will be resolved once I get around to it.
>
> I sent this change to Matt first, to check if it was right, since he is
> the VM guru and whatnot. Also, the change was made quite a while ago.
> Before we entered the freeze, IIRC. IMHO, backing it out will just make
> more and more apps use it, and it will be totally sad -- but hey, I am
> not Release Engineer, so final decision is up to you.
>
> Cheers.
>
> P.S. Apologies for taking long to reply, I was out party-ing. :^)
>
> --
> Hiten Pandya (hiten@unixdaemons.com, hiten@uk.FreeBSD.org)
> http://www.unixdaemons.com/~hiten/
Ok, I agree that the naming could cause confusion since there is a
vmmeter struct and a vmtotal struct. However, the Release Engineering
policy that was set out at the start of RELENG_5_0 is that public API
changes need review. I'm not saying that those reviews won't be
approved, but we want to keep the pain involved in 5.0->5.1 as low
as possible. This is causing pain with several high-profile ports.
In my opinion, the inconsistency in VM_METER was annoying, but
not enough to justify breaking an interface that has been existence
since _1994_. Dude, that is _9_ years. If you'd like the name to
change, lets hold of for RELENG_5 to happen. Please back out the
name change.
Scott
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