RFR (XXS): 8165153: Crash in rebuild_cpu_to_node_map

David Holmes david.holmes at oracle.com
Wed Sep 7 06:21:28 UTC 2016

Thanks Robbin.


On 7/09/2016 4:06 PM, Robbin Ehn wrote:
> Looks good!
> /Robbin
> On 09/07/2016 03:00 AM, David Holmes wrote:
>> webrev: http://cr.openjdk.java.net/~dholmes/8165153/webrev/
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8165153
>> The NUMA rebuild_cpu_to_node_map code is intended to map from physical
>> CPU ID's to nodes on a system. To determine how many CPUs there are it
>> uses os::active_processor_count(). That is actually incorrect as it
>> needs to how many CPUs the system has, not how many have been made
>> available to the JVM. This worked** in the past because the
>> active_processor_count() returned the number of online CPUs. However,
>> after the fix for 6515172, it returned the number of available CPUs, as
>> it should.
>> The fix is to change that code to use processor_count(), which is the
>> number of configured CPUs on the system.
>> Thanks,
>> David
>> ** The old code would likely also fail if the number of online CPUs
>> dynamically increased after the JVM was started!

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