Re: Windows 8 Release Preview. fork problems with rsync

[Corinna Vinschen <corinna-cygwin@cygwin.com>]

On Jun  7 10:35, Ryan Johnson wrote:
> On 06/06/2012 12:12 PM, Corinna Vinschen wrote:
> >On Jun  6 16:41, Bertrand Latinville wrote:
> >>I'm using
> >>
> >>  rsync --chmod=ug=rwX -arvz --prune-empty-dirs  --include="*/"
> >>--include-from=include-file.txt  --exclude="*" ${source_dir}/
> >>${dest_dir}
> >Thanks.  I can confirm the effect.  For no apparent reason, the OS
> >reserves a 1 Megs shared memory region, top-down allocated, of which it
> >uses about 20K.  It's not the PEB or one of the TEBs, though.  Nor is
> >it a thread stack.  I checked, and it turns out that it's allocated
> >in every process, on 32 and 64 bit systems.  That's kind of worrying
> >since that's bound to collide with mmaped regions and pthread stacks a
> >lot.  I don't know what to do at this point.
> Given that the OS always gets there first, why not just adjust
> Cygwin's definition of "top" for win8? Or does heap randomization
> move that mystery chunk around?

Yes, the chunk is moved around.  Thousands of tests show a lowest
memory slot, but the problem is that top-down allocation is not a
manual functionality done by Cygwin.  It's just a flag in calls
to VirtualAlloc or MapViewOfFileEx.  Therefore, if we have to define
our own highest memory slot, it requires Cygwin to do some trickery
on its own, which was just not necessary so far.

I'm going to ask Microsoft about this issue first.  Maybe it's 
something only in the release preview which will go away in the
gold release.  If so, I won't start to workaround it.


Corinna


-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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