Date: Fri, 13 Apr 2001 09:28:27 +0200 From: Poul-Henning Kamp <phk@critter.freebsd.dk> To: Matt Dillon <dillon@earth.backplane.com> Cc: Rik van Riel <riel@conectiva.com.br>, David Xu <bsddiy@21cn.com>, freebsd-hackers@FreeBSD.ORG Subject: Re: vm balance Message-ID: <64013.987146907@critter> In-Reply-To: Your message of "Thu, 12 Apr 2001 14:24:36 PDT." <200104122124.f3CLOaq25845@earth.backplane.com>
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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
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