Date: Sun, 23 Sep 2001 12:47:02 +0200 From: Wilko Bulte <wkb@freebie.xs4all.nl> To: Matt Dillon <dillon@earth.backplane.com> Cc: Poul-Henning Kamp <phk@critter.freebsd.dk>, David Greenman <dg@root.com>, Seigo Tanimura <tanimura@r.dl.itc.u-tokyo.ac.jp>, bright@wintelcom.net, hackers@FreeBSD.ORG Subject: Re: Conclusions on... was Re: More on the cache_purgeleafdirs() routine Message-ID: <20010923124702.B9914@freebie.xs4all.nl> In-Reply-To: <200109231040.f8NAeXw86352@earth.backplane.com>; from dillon@earth.backplane.com on Sun, Sep 23, 2001 at 03:40:33AM -0700 References: <96469.1001237641@critter> <200109231040.f8NAeXw86352@earth.backplane.com>
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On Sun, Sep 23, 2001 at 03:40:33AM -0700, Matt Dillon wrote: > > :> VM Page Cache, and thus not be candidates for reuse anyway. So my patch > :> has a very similar effect but without the overhead. > : > :Back when I rewrote the VFS namecache back in 1997 I added that > :clause because I saw directories getting nuked in no time because > :there were no pages holding on to them (device nodes were even worse!) > : > :So refresh my memory here, does directories get pages cached in VM if > :you have vfs.vmiodirenable=0 ? > : > :What about !UFS filesystems ? Do they show a performance difference ? > : > :Also, don't forget that if the VM system gave preferential caching to > :directory pages, we wouldn't need the VFS-cache very much in the first > :place... > : > :-- > :Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > > Ah yes, vmiodirenable. We should just turn it on by default now. I've Has the problem of small-memory machines (< 64M IIRC) solved now? As I understand it vmiodirenable is counter-productive for these boxes. Maybe one could decide on-boot whether the amount of mem is enough to make it useful? Just a thought of course. > been waffling too long on that. With it off the buffer cache will > remember at most vfs.maxmallocspace worth of directory data (read: not > very much), and without VMIO backing, which means vnodes could be > reclaimed immediately. Ah! Now I see why that clause was put > in... but it's obsolete now if vmiodirenable is turned on, and it > doesn't scale well to large-memory machines if it is left in. -- | / o / /_ _ email: wilko@FreeBSD.org |/|/ / / /( (_) Bulte Arnhem, The Netherlands To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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