Re: Large arrays (again), problem case for GNAT

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Thu, 14 Apr 2005 05:11:56 +0400 (MSD), Alexander E. Kopilovich wrote:

> Robert A Duff wrote;
> 
>> "(see below)" <yaldnif.b@blueyonder.co.uk> writes:
>>
>>> I see that Adrian is using Linux.
>>> Is Linux not notorious for problems of this kind?
>>> 
>>> I seem to remember that it has some kind of optimistic allocator
>> that can grant a memory allocation request, only for it to fail
>> when you try to use the memory you appear to have been granted.
>>
>>...
>>
>> I'm not sure why you say "notorious".  It seems to me that
>> allocate-on-write is desirable.
> 
> So, what is the meaning of malloc call with this approach? In which court
> (somewhere in Linux or outside) I should defend my right to use the memory,
> which I legally requested by malloc, was granted, and then deprived of it?

It is a well known and very old design flaw of many OSes including Linux,
that successful allocation does not give you any amount of virtual memory
until you commit the pages. It is not memory you are granted, it is even
not virtual memory, it is address space which is worth of nothing. This
controversy is as old as in-out parameters of Ada functions...

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de