So the problem is only with the data structures on the heap that are pinned in place to play nice with C?
I'd be curious to understand the change too, though per se pinned memory (a la storable or or bytestring) will by definition cause memory fragmentation in a gc'd lang as a rule, (or at least one like Haskell).
-Carter
On Thu, Sep 20, 2012 at 8:59 PM, John Lato
<jwlato@gmail.com> wrote:
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.
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