Date: Mon, 8 Aug 2005 03:05:33 +0800 From: Xin LI <delphij@frontfree.net> To: Chuck Swiger <cswiger@mac.com> Cc: freebsd-performance@FreeBSD.org Subject: Re: [RFC] Bumping ufs.dirhash_maxmem to a larger value? Message-ID: <20050807190533.GA61954@frontfree.net> In-Reply-To: <42F659AE.80905@mac.com> References: <20050807184707.GA61714@frontfree.net> <42F659AE.80905@mac.com>
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--Kj7319i9nmIyA2yE Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sun, Aug 07, 2005 at 02:57:50PM -0400, Chuck Swiger wrote: [snip] > On the other hand, I've got several firewall boxes with only 128MB, and= =20 > it's not reasonable to simply dedicate up to 64MB (half!) to dirhash=20 > without paying more attention to the amount of physical memory that is=20 > actually available. Forgot to mention that dirhash_maxmem is the upper limit, not the exact amount that dirhash must use. If your firewall does not host zillion of large directories then a bigger default dirhash_maxmem would essentially a big no-op :-) > How big should dirhash_maxmem be? 5-10% of available RAM, perhaps? Actually this depends on how many large directories that you actively access, not only the available RAM. If you access only a little of small directories, e.g. hosting a database, then dirhash won't help much. But with a lot of large directories having 1000+ files in most of them, then raising the dirhash_maxmem will be a great help for performance. I think it would be great if we can implement a automatical "suggested value" of dirhash during bootstrap stage, though, which can be overridden through sysctl.conf or subsequent sysctl. Cheers, --=20 Xin LI <delphij frontfree net> http://www.delphij.net/ See complete headers for GPG key and other information. --Kj7319i9nmIyA2yE Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.1 (FreeBSD) iD8DBQFC9lt9/cVsHxFZiIoRAm/kAJ9UZLf+FAk55+YA5BcEs3Su5IZTAACfRwzS ydUrVCocULNSkEkdUBlk2Ps= =eame -----END PGP SIGNATURE----- --Kj7319i9nmIyA2yE--
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