Add mblocks_allocated to GC stats API

This exposes mblocks_allocated in the GCStats struct.

Test Plan: it builds

Reviewers: bgamari, simonmar, austin, hvr, erikd

Reviewed By: erikd

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2429

includes/rts/storage/GC.h

@@ -237,6 +237,7 @@ typedef struct _GCStats {
   StgWord64 current_bytes_slop;
   StgWord64 max_bytes_slop;
   StgWord64 peak_megabytes_allocated;
+  StgWord64 mblocks_allocated;
   StgWord64 par_tot_bytes_copied;
   StgWord64 par_max_bytes_copied;
   StgDouble mutator_cpu_seconds;

libraries/base/GHC/Stats.hsc

@@ -72,6 +72,7 @@ data GCStats = GCStats
     , peakMegabytesAllocated :: !Int64
     -- | CPU time spent running mutator threads.  This does not include
     -- any profiling overhead or initialization.
+    , mblocksAllocated :: !Int64 -- ^ Number of allocated megablocks
     , mutatorCpuSeconds :: !Double
 
     -- | Wall clock time spent running mutator threads.  This does not
@@ -131,6 +132,7 @@ getGCStats = do
     currentBytesSlop <- (# peek GCStats, current_bytes_slop) p
     maxBytesSlop <- (# peek GCStats, max_bytes_slop) p
     peakMegabytesAllocated <- (# peek GCStats, peak_megabytes_allocated ) p
+    mblocksAllocated <- (# peek GCStats, mblocks_allocated) p
     {-
     initCpuSeconds <- (# peek GCStats, init_cpu_seconds) p
     initWallSeconds <- (# peek GCStats, init_wall_seconds) p

rts/Stats.c

@@ -883,6 +883,7 @@ extern void getGCStats( GCStats *s )
     s->max_bytes_used = max_residency*sizeof(W_);
     s->cumulative_bytes_used = cumulative_residency*(StgWord64)sizeof(W_);
     s->peak_megabytes_allocated = (StgWord64)(peak_mblocks_allocated * MBLOCK_SIZE / (1024L * 1024L));
+    s->mblocks_allocated = (StgWord64)mblocks_allocated;
     s->bytes_copied = GC_tot_copied*(StgWord64)sizeof(W_);
     s->max_bytes_slop = max_slop*(StgWord64)sizeof(W_);
     s->current_bytes_used = current_residency*(StgWord64)sizeof(W_);