Hello, We've noticed that some applications exhibit significantly worse memory usage when compiled with ghc-7.6.1 compared to ghc-7.4, leading to out of memory errors in some cases. Running one app with +RTS -s, I see this: ghc-7.4 525,451,699,736 bytes allocated in the heap 53,404,833,048 bytes copied during GC 39,097,600 bytes maximum residency (2439 sample(s)) 1,547,040 bytes maximum slop 628 MB total memory in use (0 MB lost due to fragmentation) ghc-7.6 512,535,907,752 bytes allocated in the heap 53,327,184,712 bytes copied during GC 40,038,584 bytes maximum residency (2391 sample(s)) 1,456,472 bytes maximum slop 3414 MB total memory in use (2744 MB lost due to fragmentation) The total memory in use (consistent with 'top's output) is much higher when built with ghc-7.6, due entirely to fragmentation. I've filed a bug report (http://hackage.haskell.org/trac/ghc/ticket/7257, http://hpaste.org/74987), but I was wondering if anyone else has noticed this? I'm not entirely sure what's triggering this behavior (some applications work fine), although I suspect it has to do with allocation of pinned memory. John L.