Potential problem with Big Pages feature on HP Tru64 UNIX V5.1B-1/PK3 and 5.1B-2/PK4



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 Advisory Information

RELEASE DATE: 24 May 2005


This Engineering Advisory supersedes previous EA BU040915_EW02.

A number of  Tru64 UNIX customers have reported system crashes while running Tru64 UNIX 5.1B-1/PK3 and 5.1B-2/PK4 on platforms with 'Big Pages' enabled. Please note that the 'Big Pages' feature is, by default, disabled on Tru64 UNIX, so most users will not encounter this situation. We are actively working to determine the root cause and to provide a solution.

If your customer encounters this problem they should immediately enter a problem report. In such cases, it is essential that L1 and L2 support engineering provide a full sys_check -escalate at the time of the crash. Please refer to the Tru64 Engineering case submission template for the location to forward all related case files.

There are two types of hash failed problems that we have been working on:

  • ubc_wire: hash failed
  • ubc_bigpage_alloc: hash failed

We have workarounds for each.

For the first type of hash failure (ubc_wire: hash failed) the system is trying to deal with replicated pages on a non-NUMA system. A valid workaround is to disable page replication for user code, which is done by changing the following sysconfig parameter and rebooting:


replicate_user_text = 0

This workaround should only be applied to non-NUMA systems. There should be no negative performance impact. The only expected outcome of this change is no more panics of this nature. There have been no reports of this failure on Sierra clusters but there is no risk to setting this tunable on Sierra systems.

For the other panic (ubc_bigpage_alloc: hash failed), we recommend disabling the segmentation tunable within Big Pages. This action also allows users to avoid a kernel memory fault from pmap_remove_all().

In sysconfig, make the following changes, then reboot:


vm_bigpg_enabled = 1

vm_bigpg_seg = 0

Target Audience: Any customer running 5.1B-1/PK3 or 5.1B-2/PK4.


The following versions are affected:

  • HP Tru64 UNIX 5.1B-2/PK4
  • HP Tru64 UNIX 5.1B-1/PK3

No fix is available at this time. When a fix is available a separate Engineering Advisory (EA) and Early Release Patch (ERP) will be issued for each affected version.