Tweak compaction candidate selection to avoid keeping page with low occupancy around.

Tweak compaction candidate selection to avoid keeping page with low occupancy around.

Increase slots buffer chain length to 15 to make compaction more aggressive and usefull.

Pass gc and collector selection reasons to GCTracer to allow more meaningull --gc-trace.

Print fragmentation of spaces that we do not compact.

R=erik.corry@gmail.com

Committed: https://code.google.com/p/v8/source/detail?r=10601

[Erik Corry, 2012-02-03 10:12:39]

LGTM

https://chromiumcodereview.appspot.com/9323007/diff/1/src/mark-compact.cc
File src/mark-compact.cc (right):

https://chromiumcodereview.appspot.com/9323007/diff/1/src/mark-compact.cc#new...
src/mark-compact.cc:578: space->CountFreeListItems(p, &sizes);
This call worries me.  It can potentially take a long time, and really all we
need to know is whether there is a small number of live objects on the page.  If
the page consists of 100k objects and 100k gaps then we are not interested in it
for the purposes of REDUCE_MEMORY_FOOTPRINT.  So I think CountFreeList should
take a maximum number of free list nodes to traverse.

I think the other 2 places this is used would also benefit from a max argument.