Parallel GC thread priority

Dmytro Sheyko dmytro_sheyko at
Fri Sep 7 15:17:23 UTC 2012


I can see that Parallel GC works on threads with NormPriority, while CMS and G1 threads run with NearMaxPriority. This probably not an issue if java application works alone, but some time ago I observed GC log like this (it was Jenkins CI on Windows):

[Full GC [PSYoungGen: 10352K->0K(171904K)] [PSOldGen: 403417K->114637K(415872K)] 413769K->114637K(587776K) [PSPermGen: 76315K->76315K(83968K)], 30.2595731 secs] [Times: user=0.77 sys=0.41, real=30.26 secs]

Despite cpu time for GC was just 1.18 sec (= 0.77 + 0.41), the real time was 30.26 sec! It seems to me that the system was busy that time and GC threads was starving.

If we could raise priority of Parallel GC threads, other application would have less impact on GC duration.

What do you think?

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