Long Format Directory Listing 15x Slower in FreeBSD 5.x
Kris Kennaway
kris at obsecurity.org
Mon Sep 12 17:51:48 PDT 2005
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.
Kris
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