From owner-freebsd-arch  Mon Jan 15 11:14:57 2001
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Date: Mon, 15 Jan 2001 11:14:39 -0800
From: Alfred Perlstein <bright@wintelcom.net>
To: Hajimu UMEMOTO <ume@FreeBSD.org>
Cc: arch@FreeBSD.org
Subject: Re: dynamic vs static sysctls?
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* Hajimu UMEMOTO <ume@FreeBSD.org> [010115 10:51] wrote:
> >>>>> On Mon, 15 Jan 2001 10:37:57 -0800
> >>>>> Alfred Perlstein <bright@wintelcom.net> said:
> 
> bright> Well all the sysctl's I've added have been dynamic, I think the
> bright> only reason for the 'static' sysctls is to give sysctl() a
> bright> numeric way to get at the sysctls, which isn't very useful 
> bright> when we have getsysctlbyname().
> 
> You mean dynamic sysctl is just use of OID_AUTO, right?  I thought
> SYSCTL_ADD_INT().
> 
> bright> Using a dynamic sysctl It would reduce the delta by quite a bit.
> 
> Indeed.
> 
> bright> The stuff your patch does seems to allow programs to use the old
> bright> (IMHO) depricated sysctl() versus getsysctlbyname() function.
> 
> bright> No one I know wants to use sysctl instead of getsysctlbyname afaik,
> bright> however, I would like to know if my opinions are the what we're
> bright> aiming for.
> 
> Okey, I'll change to use OID_AUTO.

Just do this:

static unsigned int nforks = 0;
SYSCTL_UINT(_kern, OID_AUTO, nforks, CTLFLAG_RD, &nforks, 0,
	"number of fork()s since boot");

document the sysctl. :)

> 
> bright> Any other comments?
> 
> One question.  How can I detect newly added sysctl?  In static, I can
> just do by #ifdef OID.

Oh, you mean in a kernel module?  I think you need to use
kernel_sysctl() (from kern/kern_sysctl.c), I'm not sure if it's
documented anywhere, if not it'd be nice to have a sysctl(9) manpage.
:)

> bright> Besideds the way the sysctl is done, the change is pretty nice
> bright> to see, but will need mplocking later.
> 
> Do you mean ALLPROC_LOCK(AP_EXCLUSIVE) / ALLPROC_LOCK(AP_RELEASE) ?
> If so, I'll move nforks++ between them.

No, don't do that, we'll figure out how to lock it later, you may
want to use the mp_fixme (mpfixme?) macro near the sysctl variable
though.

-- 
-Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org]
"I have the heart of a child; I keep it in a jar on my desk."


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