Date: Sun, 23 Sep 2001 15:06:36 +0200 From: Poul-Henning Kamp <phk@critter.freebsd.dk> To: Matt Dillon <dillon@earth.backplane.com> Cc: 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: <98331.1001250396@critter> In-Reply-To: Your message of "Sun, 23 Sep 2001 03:40:33 PDT." <200109231040.f8NAeXw86352@earth.backplane.com>
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In message <200109231040.f8NAeXw86352@earth.backplane.com>, Matt Dillon writes: > Ah yes, vmiodirenable. We should just turn it on by default now. I've > 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. > > If we turn vmiodirenable on then directory blocks get cached by the > VM system. There is no preferential treatment of directory blocks > but there doesn't need to be, the VM system does a very good job figuring > out which blocks to keep and which not to. Well, benchmarks will show that. A directory page may hold the access to hundred files so it should not be pushed out by one file. I think getting directory pages VM cached is The Right Way for this, because it means that also the not-earlier used filenames become cheaply accessible. Things to look out for: 1. !ufs filesystems 2. inode->vnode hash/search algorithms may become much more important. -- 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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