Compact Regions

This brings in initial support for compact regions, as described in the
ICFP 2015 paper "Efficient Communication and Collection with Compact
Normal Forms" (Edward Z. Yang et.al.) and implemented by Giovanni
Campagna.

Some things may change before the 8.2 release, but I (Simon M.) wanted
to get the main patch committed so that we can iterate.

What documentation there is is in the Data.Compact module in the new
compact package.  We'll need to extend and polish the documentation
before the release.

Test Plan:
validate
(new test cases included)

Reviewers: ezyang, simonmar, hvr, bgamari, austin

Subscribers: vikraman, Yuras, RyanGlScott, qnikst, mboes, facundominguez, rrnewton, thomie, erikd

Differential Revision: https://phabricator.haskell.org/D1264

GHC Trac Issues: #11493

1 files changed, 23 insertions, 0 deletions

diff --git a/rts/ProfHeap.c b/rts/ProfHeap.c
index 664ee50d70..956a250747 100644
--- a/rts/ProfHeap.c
+++ b/rts/ProfHeap.c
@@ -940,6 +940,24 @@ static void heapProfObject(Census *census, StgClosure *p, size_t size,
             }
 }
 
+// Compact objects require special handling code because they
+// are not stored consecutively in memory (rather, each object
+// is a list of objects), and that would break the while loop
+// below. But we know that each block holds at most one object
+// so we don't need the loop.
+//
+// See Note [Compact Normal Forms] for details.
+static void
+heapCensusCompactList(Census *census, bdescr *bd)
+{
+    for (; bd != NULL; bd = bd->link) {
+        StgCompactNFDataBlock *block = (StgCompactNFDataBlock*)bd->start;
+        StgCompactNFData *str = block->owner;
+        heapProfObject(census, (StgClosure*)str,
+                       compact_nfdata_full_sizeW(str), rtsTrue);
+    }
+}
+
 /* -----------------------------------------------------------------------------
  * Code to perform a heap census.
  * -------------------------------------------------------------------------- */
@@ -1116,6 +1134,10 @@ heapCensusChain( Census *census, bdescr *bd )
                 size = sizeofW(StgTRecChunk);
                 break;
 
+            case COMPACT_NFDATA:
+                barf("heapCensus, found compact object in the wrong list");
+                break;
+
             default:
                 barf("heapCensus, unknown object: %d", info->type);
             }
@@ -1153,6 +1175,7 @@ void heapCensus (Time t)
       // Are we interested in large objects?  might be
       // confusing to include the stack in a heap profile.
       heapCensusChain( census, generations[g].large_objects );
+      heapCensusCompactList ( census, generations[g].compact_objects );
 
       for (n = 0; n < n_capabilities; n++) {
           ws = &gc_threads[n]->gens[g];