Red Hat Bugzilla – Bug 178839
CPU's being incorrectly numbered
Last modified: 2014-08-14 21:43:03 EDT
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Description of problem:
4-node IBM x460 each with 4 physical dual-core cpu's with hyperthreading enabled.
cat'ing /proc/cpuinfo only reports 32 logical cpu's, where we would expect 64.
dmesg output shows that the cpu's are not being sequentially numbered. As a result, some are being incorrectly numbered as being above #128 & thus are not being utilised, eg:
ACPI: LAPIC (acpi_id[0x20] lapic_id[0x80] enabled)
Processor #128 invalid (max 128)
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. boot system with largesmp kernel
Created attachment 123626 [details]
output from "cat /proc/cpuinfo"
Created attachment 123627 [details]
I should add that with hyperthreading disabled, only 16 logical cpu's are reported.
This is a duplicate of Bug 177561. The CPUs are in fact being numbered
correctly. The problem is that the kernel only recognized a maximum CPU id of
128 when in fact the hardware limit is 255.
The 460 in particular implements "sparse" numbering of CPUs; each successive
node starts numbering CPUs at the next multiple of 64, which is why half of the
CPUs are in the 128-255 range and thus unused.
A patch has already been committed for this.
*** This bug has been marked as a duplicate of 177561 ***
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.