Date: Wed, 29 Mar 2006 17:54:42 +0000 (GMT) From: Robert Watson <rwatson@FreeBSD.org> To: Dag-Erling =?iso-8859-1?Q?Sm=F8rgrav?= <des@des.no> Cc: Chris <chrcoluk@gmail.com>, "Conrad J. Sabatier" <conrads@cox.net>, freebsd-stable@freebsd.org, bmilekic@freebsd.org Subject: Re: nmbclusters Message-ID: <20060329175256.W19236@fledge.watson.org> In-Reply-To: <861wwlcsnj.fsf@xps.des.no> References: <3aaaa3a0603281134sd0d4e16x@mail.gmail.com> <20060329030459.40be9cb2.conrads@cox.net> <861wwlcsnj.fsf@xps.des.no>
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On Wed, 29 Mar 2006, Dag-Erling Smørgrav wrote: > "Conrad J. Sabatier" <conrads@cox.net> writes: >> Chris <chrcoluk@gmail.com> wrote: >>> so [kern.ipc.nmbclusters] has no affect, has this become a read only >>> tunable again only settable in loader.conf? >> To the best of my knowledge, this has *always* been a loader tunable, >> not configurable on-the-fly. > > kern.ipc.nmbclusters is normally computed at boot time. A compile- time > option to override it was introduced in 2.0-CURRENT. At that time, it was > defined in param.c. A read-only sysctl was introduced in 3.0-CURRENT. It > moved from param.c to uipc_mbuf.c in 4.0-CURRENT, then to subr_mbuf.c when > mballoc was introduced in 5.0-CURRENT; became a tunable at some point after > that; then moved again to kern_mbuf.c when mballoc was replaced with mbuma > in 6.0-CURRENT. That is the point where it became read-write, for no good > reason that I can see; setting it at runtime has no effect, because the size > of the mbuf zone is determined at boot time. Perhaps Bosko (who wrote both > mballoc and mbuma, IIRC) knows. Paul Saab from Yahoo! has a set of patches that allow run-time nmbclusters changes to be implemented -- while it won't cause the freeing of clusters referenced, it goes through and recalculates dependent variables, propagates them into UMA, etc. I believe they're running with this patch on 6.x, and I expect that they will be merged to -CURRENT and -STABLE in the relatively near future. Not before 6.1, however. If the nmbclusters setting really has no effect right now, we should mark the sysctl as read-only to make it more clear it doesn't, since allowing it to be set without taking effect is counter-intuitive. Robert N M Watson
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