Add +RTS -AL<size>

+RTS -AL<size> controls the total size of large objects that can be
allocated before a GC is triggered.  Previously this was always just the
value of -A, and the limit mainly existed to prevent runaway allocation
in pathalogical programs that allocate a lot of large objects.  However,
since the limit is shared between all cores, on a large multicore the
default becomes more restrictive, and can end up triggering GC well
before it would normally have been.

Arguably a better default would be A*N, but this is probably excessive.
Adding a flag lets you choose, and I've left the default as it was.

See docs for usage.

1 files changed, 5 insertions, 2 deletions

diff --git a/rts/sm/Storage.c b/rts/sm/Storage.c
index 18ae796864..3e421a6e9b 100644
--- a/rts/sm/Storage.c
+++ b/rts/sm/Storage.c
@@ -179,8 +179,11 @@ initStorage (void)
   debug_caf_list = (StgIndStatic*)END_OF_CAF_LIST;
   revertible_caf_list = (StgIndStatic*)END_OF_CAF_LIST;
    
-  /* initialise the allocate() interface */
-  large_alloc_lim = RtsFlags.GcFlags.minAllocAreaSize * BLOCK_SIZE_W;
+  if (RtsFlags.GcFlags.largeAllocLim > 0) {
+      large_alloc_lim = RtsFlags.GcFlags.largeAllocLim * BLOCK_SIZE_W;
+  } else {
+      large_alloc_lim = RtsFlags.GcFlags.minAllocAreaSize * BLOCK_SIZE_W;
+  }
 
   exec_block = NULL;