RE: 2.1.17 performance issues

["Howard Chu" <hyc@highlandsun.com>]

> -----Original Message-----
> From: xoror@infuse.org [mailto:xoror@infuse.org]

> On Wed, 16 Apr 2003, Howard Chu wrote:
> > Since you say that the performance degradation persists past a directory
> > restart, it sounds like your BDB environment has run out of resources.
You
> > should examine the statistics that db_stat provides. You should read the
> > SleepyCat documentation on how to use the Berkeley DB library.
>
> I have gone through the cache settings again and now have solved my
> problem. The DB_CONFIG needs to be set before you create anything.
> A cache file on disk will be created. This explains why a
> restart of slapd doesn't help a thing.

> I still have a question left. Why is the cache maintained on disk? Why is
> swapping out old pages/entries and swapping in new pages/entries so slow?
> Does this imply when you have a large cachefile swapping out/in takes a
> lot longer then a small cache file ?

These questions about why/how BerkeleyDB works are beyond the scope of this
mailing list. You might try finding someone at sleepycat.com to answer them
for you. In brief, BDB with transactions is designed to support reliable
database updates, such that changes persist and are not lost even if there
are other failures in the software or hardware environment. If you don't care
about persistence and recoverability you can leave your database environment
in a RAMdisk/tmpfs etc. or recompile back-bdb to use shared memory instead of
the on-disk cache. Doing so will leave you fairly vulnerable to power
failures and other common mishaps.

  -- Howard Chu
  Chief Architect, Symas Corp.       Director, Highland Sun
  http://www.symas.com               http://highlandsun.com/hyc
  Symas: Premier OpenSource Development and Support