Red Hat Bugzilla – Bug 174760
Provide support for more than 8 logical processors
Last modified: 2013-03-06 00:59:22 EST
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Description of problem:
Currently, RHEL 4.0 only supports a maximum of eight logical processors for the 64-bit x86_64 (AMD64/EM64T) architecture. (On the 32-bit x86 architecture, 32 logical processors are supported.)
These limits are outlined on the following Red Hat page:
With the release of new multi-core processors from Intel and AMD, and new hardware from vendors supporting large numbers of processor cores, this limit is quickly becoming problematic.
For example, a multi-processor system containing 4 Intel dual core processors (e.g., Paxville) with hyperthreading enabled will show up as 16 logical processors under Linux. On x86, this works fine, but on x86_64, only 8 logical processors show up, and hyperthreading is effectively disabled.
Worse yet, on a multi-processor system containing 8 AMD dual core processors you effectively lose access to half the cores in the system under x86_64.
Intel and systems vendors assure me that Red Hat is aware of this problem and that fixes are being planned, but I've been unable to locate a bugzilla bug which is tracking this need. Thus, I'm opening this bug. If there is some internal/hidden bug to track this development, please feel free to dupe the bug. (Note that this bug is similar/related to but NOT a duplicate of Bug 147823.)
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. Install RHEL 4.0 x86_64 on a system with more than eight logical processors.
2. cat /proc/cpuinfo
Actual Results: Only eight logical processors will be listed.
Expected Results: All available logical processors should be listed.
*** This bug has been marked as a duplicate of 163641 ***
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 the 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.