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, > > > > We have been trying to migrate to FreeBSD 5.4 from an older 4.x release > > for one of our busy mail servers. But we have encountered problems with > > directory listings on 5.4. > > > > Our /var/mail directory contains approximately 8,000 files doing a long > > directory listing (ls -l) takes approximately 5 min and during this time > > the CPU is running near 100%, on a FSBD 4 box the same directory > > contents takes less than 20 seconds to list. Even on a directory with > > 200 files, each file with a different owner, it will still take at least > > 4-5 seconds to list. The problems only seems to occur when the directory > > contains files from many different users. (as in /var/mail). If I chown > > all the files in the /var/mail directory to a single user the directory > > listing is near instant. > > > > It appears it has something to do with 'ls' looking up the id's in the > > password database, because if I instruct ls to display numeric IDs (ls > > -ln), rather than converting to user and group names, the directory with > > 8,000 files, with 8,000 different owners will list instantly. > > > > The reason this concerns me so much is we are also having a problem with > > our Washington IMAP / POP3 server on FBSD 5 using a lot of CPU while > > operating on small and even 0 byte mailboxes, when there are approx five > > or more concurrent POP3 or IMAP sessions. And I can't help thinking that > > the two problems are related. > > > > Does anyone have any ideas? Has anyone else noticed this problem? If I > > can't resolve it I'm most likely going to revert to using 4.11, but I'd > > really like to know what is going on. (and yes I'm using UFS_DIRHASH) > > 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 -- 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
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