With JDK8 it seems to be impacted by whether the machine has multiple nodes
(or not):
$ numactl -H
available: 2 nodes (0-1)
node 0 cpus: 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42
44 46
node 0 size: 63560 MB
node 0 free: 24246 MB
node 1 cpus: 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43
45 47
node 1 size: 64497 MB
node 1 free: 26020 MB
node distances:
node 0 1
0: 10 21
1: 21 10
$ java -XX:+PrintFlagsFinal -XX:+UseNUMA -version | grep UseNUMA
bool UseNUMA := true
{product}
bool UseNUMAInterleaving := true
$ numactl -H
available: 1 nodes (0)
node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
24 25 26 27
node 0 size: 64342 MB
node 0 free: 25173 MB
node distances:
node 0
0: 10
$ java -XX:+PrintFlagsFinal -XX:+UseNUMA -version | grep UseNUMA
bool UseNUMA := false
{product}
bool UseNUMAInterleaving = false
{product}
On Wed, 28 Aug 2019 at 09:05, Ben Evans <[email protected]>
wrote:
> Hi,
>
> I've encountered an issue whereby, despite -XX:+UseNuma being
> explicitly set on the command line, the final flags list that is seen
> has it disabled. This is on OpenJDK 8u212.
>
> Has anyone encountered a runtime configuration or sequence of flags
> that will disable NUMA-awareness as a side-effect?
>
> I'll see if I can pull the exact startup flags as given and share them.
>
> Any pointers gratefully received.
>
> Thanks,
>
> Ben
>
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