Number of Parallel GC Threads

Clemens Eisserer linuxhippy at
Fri Jan 23 15:36:23 UTC 2009

Hi Nicolas,

> However, we also have some little Java-based agents running on our systems which
> just use the defaults. On our T5240's and T5440's they end up having 128 resp.
> 256 parallel gc threads! I'm wondering whether this is really a "reasonable"
> default behavior?! Would someone really run just one JVM on such a large system?
> Does it make sense to have 256 parallel gc threads as a *default* on such
> servers?

Well, except a bit of wasted memory (because each thread has its own
private data structures) I think it does not hurt a lot.
It should be a rather rare case that two JVMs running run a gc-cycle
at the same time for which performance will be a bit worse, however
when there are no gc-cycle "collisions" each JVM will have lowest
possible gc pause time.

- Clemens

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