Description of problem: For large maps (6000+ entries) we need to decrease hash chain size to improve performance, which we should be able to do by increasing the hash table size. Unfortunately, the additive hashing algorithm used by autofs results in a clustering of hash values around the average hash chain size. It is biased toward a small range of hash indexes which becomes more of a problem as the hash table size increases. Testing shows that the "One-at-a-time" hash function gives a much better distribution of hash indexes as table size increases. This change has been implemented upstream and should also be done in RHEL-5 autofs.
Release note added. If any revisions are required, please set the "requires_release_notes" flag to "?" and edit the "Release Notes" field accordingly. All revisions will be proofread by the Engineering Content Services team. New Contents: Previously, the additive hashing algorithm used by autofs to generate hash values would result in a clustering of values that favoured a small range of hash indexes and led to reduced performance in large maps. Autofs now uses a "one-at-a-time" hash function which gives a better distribution of hash values in large hash tables. Use of the "one-at-a-time" hash function safeguards lookup performance as maps increase to 8,000 entries and beyond.
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHBA-2009-1397.html