Re: Chat with Wesley Terpstra

On Thu, Apr 29, 2010 at 6:22 PM, Wesley W. Terpstra <[email protected]>wrote:

>  One thing that you could check is the behavior of this memory leak program
>> on x86-mingw (on a machine with >4GiB memory):
>>
>>  fun loop (l,w) =
>>     if (w = 0wx0)
>>        then let
>>                val w = List.foldl Word.xorb 0wx0 l
>>                val _ = print (concat ["w = ", Word.toString w, "\n"])
>>             in
>>                loop (l, if w = 0wx0 then 0wxAAAAAAAA else w)
>>             end
>>     else loop (w::l, w - 0wx1)
>>  val _ = loop ([], 0wxAAAAAAAA)
>>
>
All of these results come from mingw r7454 as uploaded to the Experimental
page.

I tried it on my machine with =4GB of memory running 64-bit Windows 7, but
running it as a 32-bit application. With 'may-page-heap' off, it took 20
seconds. With 'may-page-heap' on, it took 56 seconds. I've attached the
output of both runs. It doesn't manage to get any more memory with the
'may-page-heap', because my windows mremap implementation can get just as
much memory as paging to disk (it expands in place). I imagine you'd see the
same behaviour in linux with native mremap?

I also tried it on the same machine (4GB, Windows 7, 64-bit) as a 64-bit
application. With 'may-page-heap' off, it took 10 minutes before I
terminated it. With 'may-page-heap' on, it ran for over 22 minutes before I
terminated it. Unfortunately, the stderr file gets truncated when I
interrupt it.

I noticed that the no-paging varient took more than 3.6GB of physical memory
in windows task manager (enough that my system thrashed). I didn't have task
manager open for the yes-paging test. Perhaps it is overestimating the
amount of physical memory and thus not stopping at 50% as it should? Or is
it the usual last-step resize = up to 2* maximum memory? Whatever is
happening, it's not ok to push a system to thrashing with default
parameters.

I can also try the 32-bit version under XP (32-bit) if that would useful. I
expect it will behave just like it did in Windows 7 (32-bit), however. In
other words, work perfectly.

It won't be easy for me to get +GB on a mingw test machine. Well, it would
be if I went and bought more RAM, but prices are bad right now. All the
machines I have access to with more memory are running linux and I can't
just switch them as they are servers.

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