Date: Mon, 12 Sep 2005 18:33:53 -0700 From: Brooks Davis <brooks@one-eyed-alien.net> To: Kris Kennaway <kris@obsecurity.org> Cc: freebsd-stable@freebsd.org, Nikolai Schupbach <nikolai@net24.co.nz> Subject: Re: Long Format Directory Listing 15x Slower in FreeBSD 5.x Message-ID: <20050913013353.GA13778@odin.ac.hmc.edu> In-Reply-To: <20050913005144.GA46178@xor.obsecurity.org> References: <4326158B.8010502@net24.co.nz> <20050913005144.GA46178@xor.obsecurity.org>
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--Kj7319i9nmIyA2yE Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Sep 12, 2005 at 08:51:44PM -0400, Kris Kennaway wrote: > On Tue, Sep 13, 2005 at 11:55:55AM +1200, Nikolai Schupbach wrote: > > Hello, > >=20 > > We have been trying to migrate to FreeBSD 5.4 from an older 4.x release= =20 > > for one of our busy mail servers. But we have encountered problems with= =20 > > directory listings on 5.4. > >=20 > > Our /var/mail directory contains approximately 8,000 files doing a long= =20 > > directory listing (ls -l) takes approximately 5 min and during this tim= e=20 > > the CPU is running near 100%, on a FSBD 4 box the same directory=20 > > contents takes less than 20 seconds to list. Even on a directory with= =20 > > 200 files, each file with a different owner, it will still take at leas= t=20 > > 4-5 seconds to list. The problems only seems to occur when the director= y=20 > > contains files from many different users. (as in /var/mail). If I chown= =20 > > all the files in the /var/mail directory to a single user the directory= =20 > > listing is near instant. > >=20 > > It appears it has something to do with 'ls' looking up the id's in the= =20 > > password database, because if I instruct ls to display numeric IDs (ls= =20 > > -ln), rather than converting to user and group names, the directory wit= h=20 > > 8,000 files, with 8,000 different owners will list instantly. > >=20 > > The reason this concerns me so much is we are also having a problem wit= h=20 > > our Washington IMAP / POP3 server on FBSD 5 using a lot of CPU while=20 > > operating on small and even 0 byte mailboxes, when there are approx fiv= e=20 > > or more concurrent POP3 or IMAP sessions. And I can't help thinking tha= t=20 > > the two problems are related. > >=20 > > Does anyone have any ideas? Has anyone else noticed this problem? If I= =20 > > can't resolve it I'm most likely going to revert to using 4.11, but I'd= =20 > > really like to know what is going on. (and yes I'm using UFS_DIRHASH) >=20 > Sounds like the real problem is that you have >8000 users on your > machine and lookups are taking a long time. There has been discussion > of this problem and how to solve it on freebsd-questions@ several > times..I think it involves making a minor change to pwd_mkdb and > rebuilding. Please search the archives for that mailing list. If you are using NIS and have any compat options in /etc/nsswitch.conf your performance will really suck in situations like this. IIRC, the compat code is worse than O(n^2) if you look up each user and the non-compat code is close to O(n). I'd really like to stop generating nsswitch.conf entries that use compat in 7.0. -- Brooks --=20 Any statement of the form "X is the one, true Y" is FALSE. PGP fingerprint 655D 519C 26A7 82E7 2529 9BF0 5D8E 8BE9 F238 1AD4 --Kj7319i9nmIyA2yE Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iD8DBQFDJix/XY6L6fI4GtQRAgfoAJ0QZkqvtozWbB/MZeqskfPRJCmzYQCfexnd setgC2tS9De4fyECrp4cfFE= =Dmm9 -----END PGP SIGNATURE----- --Kj7319i9nmIyA2yE--
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