MaxTenuringThreshold has a new ergonomic value???

[Thomas Schatzl]

Hi,

On Mon, 2013-09-02 at 11:58 +0200, Kirk Pepperdine wrote:
> Hi,
> 
> Where does ergonomics calculate MaxTenuringhreshold for ParNew? It seems
>that I missed the memo that the default ergonomics setting for this
>flag has drifted from 4 to 6? Is this now the case?

arguments.cpp, Arguments::set_cms_and_parnew_gc_flags():

1218:   intx   tenuring_default = (intx)6;
[...]
1286:  // Unless explicitly requested otherwise, definitely
1287:  // promote all objects surviving "tenuring_default" scavenges.
1288:  if (FLAG_IS_DEFAULT(MaxTenuringThreshold) &&
1289:      FLAG_IS_DEFAULT(SurvivorRatio)) {
1290:    FLAG_SET_ERGO(uintx, MaxTenuringThreshold, tenuring_default);
1291:  }


Note that the most recent change in line 1218 of that file dates back to
March 2011.

I do not know the rationale for this change.

The RFR does not give additional details:
http://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2011-March/002384.html

Hth,
Thomas