RFR (XXS): 8165153: Crash in rebuild_cpu_to_node_map

Robbin Ehn robbin.ehn at oracle.com
Wed Sep 7 06:06:04 UTC 2016

Looks good!


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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