Make clearNursery free

Summary:
clearNursery resets all the bd->free pointers of nursery blocks to
make the blocks empty.  In profiles we've seen clearNursery taking
significant amounts of time particularly with large -N and -A values.

This patch moves the work of clearNursery to the point at which we
actually need the new block, thereby introducing an invariant that
blocks to the right of the CurrentNursery pointer still need their
bd->free pointer reset.  This should make things faster overall,
because we don't need to clear blocks that we don't use.

Test Plan: validate

Reviewers: AndreasVoellmy, ezyang, austin

Subscribers: thomie, carter, ezyang, simonmar

Differential Revision: https://phabricator.haskell.org/D318

1 files changed, 21 insertions, 1 deletions

diff --git a/rts/sm/Storage.h b/rts/sm/Storage.h
index 0016876066..943c3e39b7 100644
--- a/rts/sm/Storage.h
+++ b/rts/sm/Storage.h
@@ -88,10 +88,30 @@ void     resizeNurseriesFixed ( W_ blocks );
 W_       countNurseryBlocks   ( void );
 
 /* -----------------------------------------------------------------------------
+   Allocation accounting
+
+   See [Note allocation accounting] in Storage.c
+   -------------------------------------------------------------------------- */
+
+//
+// Called when we are finished allocating into a block; account for the amount
+// allocated in cap->total_allocated.
+//
+INLINE_HEADER void finishedNurseryBlock (Capability *cap, bdescr *bd) {
+    cap->total_allocated += bd->free - bd->start;
+}
+
+INLINE_HEADER void newNurseryBlock (bdescr *bd) {
+    bd->free = bd->start;
+}
+
+void    updateNurseriesStats (void);
+StgWord calcTotalAllocated   (void);
+
+/* -----------------------------------------------------------------------------
    Stats 'n' DEBUG stuff
    -------------------------------------------------------------------------- */
 
-void  updateNurseriesStats (void);
 W_    countLargeAllocated  (void);
 W_    countOccupied        (bdescr *bd);
 W_    calcNeeded           (rtsBool force_major, W_ *blocks_needed);