From owner-freebsd-hackers Fri Apr 13 0:30:21 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from critter.freebsd.dk (critter.freebsd.dk [212.242.86.163]) by hub.freebsd.org (Postfix) with ESMTP id 0300B37B423 for ; Fri, 13 Apr 2001 00:30:11 -0700 (PDT) (envelope-from phk@critter.freebsd.dk) Received: from critter (localhost [127.0.0.1]) by critter.freebsd.dk (8.11.3/8.11.3) with ESMTP id f3D7SRC64015; Fri, 13 Apr 2001 09:28:27 +0200 (CEST) (envelope-from phk@critter.freebsd.dk) To: Matt Dillon Cc: Rik van Riel , David Xu , freebsd-hackers@FreeBSD.ORG Subject: Re: vm balance In-Reply-To: Your message of "Thu, 12 Apr 2001 14:24:36 PDT." <200104122124.f3CLOaq25845@earth.backplane.com> Date: Fri, 13 Apr 2001 09:28:27 +0200 Message-ID: <64013.987146907@critter> From: Poul-Henning Kamp Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG In message <200104122124.f3CLOaq25845@earth.backplane.com>, Matt Dillon writes: >:>:> scaleability. >:>: >:>:Uhm, that is actually not true. >:>: >:>:We keep namecache entries around as long as we can use them, and that >:>:generally means that recreating them is a rather expensive operation, >:>:involving creation of vnode and very likely a vm object again. >:> >:> The vnode cache is a different cache. positive namei hits will >:> reference a vnode, but namei elements can be flushed at any >:> time without flushing the underlying vnode. >: >:Right, but doing so means that to refind that vnode from the name >:is (comparatively) very expensive. >: >:-- >:Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 >:phk@FreeBSD.ORG | TCP/IP since RFC 956 > > The only thing that is truely expensive is having to physically > scan a large directory in order to instantiate a new namei > record. Everything else is inexpensive by comparison (by two > orders of magnitude!), even constructing new vnodes. > > Without vmiodirenable turned on, any directory [...] It's worse than that, we are still way too rude in throwing away directory data... -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message