CRR (XS): 7089625: G1: policy for how many old regions to add to the CSet (when young gen is fixed) is broken
Tony Printezis
tony.printezis at oracle.com
Mon Sep 12 16:09:30 UTC 2011
I had to re-arrange some code when I added the ergo decision output to
G1 and I unfortunately got a condition wrong which broke the policy of
how many old regions to add to the CSet.
Could I please get a couple of quick code review for the two-line fix?
http://cr.openjdk.java.net/~tonyp/7089625/webrev.0/
I attached a description of the issue (from the CR) below.
Tony
--------------------------
The original code was:
should_continue =
( hr != NULL) &&
( (adaptive_young_list_length()) ? time_remaining_ms > 0.0
: _collection_set_size < _young_list_fixed_length );
In the fix for 7050392 I refactored it to be able to emit the correct
ergo policy output:
should_continue = true;
if (hr == NULL) {
// No need for an ergo verbose message here,
// getNextMarkRegion() does this when it returns NULL.
should_continue = false;
} else {
if (adaptive_young_list_length()) {
if (time_remaining_ms < 0.0) {
ergo_verbose1(ErgoCSetConstruction, ...);
should_continue = false;
}
} else {
if (_collection_set_size < _young_list_fixed_length) {
ergo_verbose2(ErgoCSetConstruction, ...);
should_continue = false;
}
}
}
and unfortunately I didn't negate the _collection_set_size <
_young_list_fixed_length condition. The intention of this code is: if hr
!= NULL (which means: we've just found and added an old region to the
CSet) and !adaptive_young_list_length() (which means: the young gen size
is fixed), we should carry on adding old regions to the CSet until the
CSet length (_collection_set_size) reaches the fixed young list target
length (_young_list_fixed_length). So, should_continue should be set to
false when _collection_set size >= _young_list_fixed_length, not when
_collection_set_size < _young_list_fixed_length.
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