2GB limit

Martin Pool mbp at canonical.com
Tue Oct 19 02:46:59 BST 2010


On 18 October 2010 15:57, Maritza Mendez <martitzam at gmail.com> wrote:
> This thread is getting pretty long, but I have new data on the repo which is
> tripping the OOM error.
> Again, the trunk is hosted on a lowly 512MB Lucid box.
>
> I then did a clean install of the stand-alone windows installer (2.2.1) on
> both a WinXP32 and a Win7x64 box.
>
> The OOM error occurs on a WinXP32 box with 2GB RAM when branching from the
> trunk:
>    - peak memory is 501MB, pagefaults=2.01million, just before the OOM
> error.
>
> But!  The error does not occur on a Win7x64 box with 4GB of RAM when
> branching from the trunk:
>    - peak memory is 870MB, pagefaults=2.38million, and the branch succeed
>
> And although it is risky to compare WinXP32 to Win7x64, I now believe that
> the real problem is not that I'm hitting the actual 2GB limit but that there
> isn't enough contiguous memory left to give python the 870MB it needs.
> Notice that the peak memory is about 350K until the "adding file contents"
> stage starts.  Then the peak memory skyrockets, along with the pagefaults of
> course.
>
> So... step 1 is have enough memory to go around.  Step 2 is to be able to
> use 64-bit code when the problem really is the 2GB limit.   Happily, I got
> bzr extensions built for x64 yesterday (but it needs testing).

We are probably not asking for a single 870MB block, but on win32 we
could well be running out of address space well before we run out of
usable vm.

If you get a traceback at the point where memory use is skyrocketing
(Ctrl-Pause then 'bt') that might give a clearer description of what's
causing it to be allocated.  (John may already know.)

Your progress on 64bit builds is very good to hear.  I think many
users would probably be pretty happy to have that even without shell
integration.

-- 
Martin



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